U.S. patent application number 17/160003 was filed with the patent office on 2021-05-20 for method and apparatus for estimating battery state of health.
The applicant listed for this patent is Huawei Technologies Co., Ltd.. Invention is credited to Kejie GAO, Zhe LI, Zhongxiao LIU, Zuqi LIU, Zhiwei WU, Jianbo ZHANG.
Application Number | 20210148988 17/160003 |
Document ID | / |
Family ID | 1000005370720 |
Filed Date | 2021-05-20 |
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United States Patent
Application |
20210148988 |
Kind Code |
A1 |
GAO; Kejie ; et al. |
May 20, 2021 |
METHOD AND APPARATUS FOR ESTIMATING BATTERY STATE OF HEALTH
Abstract
Estimating a battery state of health (SOH) is described. The
state of heath is estimated by obtaining a partial charge or
discharge capacity of a target battery in a state of charge (SOC)
interval of each of a plurality of SOCs. First dV/dSOC data is
separately calculated for each SOC in an m.sup.th preset battery
capacity based on the m.sup.th preset battery capacity and the
partial charge or discharge capacity in the SOC interval of each
SOC. A smallest overall dV/dSOC data deviation is determined from
all overall dV/dSOC data deviations corresponding to M preset
battery capacities. A preset battery capacity is determined
corresponding to the smallest overall dV/dSOC data deviation as a
retention capacity of an aged target battery. The retention
capacity of the aged target battery is divided by a retention
capacity of the target battery in a new battery state, to obtain
the SOH estimate of the target battery.
Inventors: |
GAO; Kejie; (Shenzhen,
CN) ; LIU; Zhongxiao; (Beijing, CN) ; ZHANG;
Jianbo; (Beijing, CN) ; LI; Zhe; (Beijing,
CN) ; WU; Zhiwei; (Shanghai, CN) ; LIU;
Zuqi; (Shenzhen, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Huawei Technologies Co., Ltd. |
Shenzhen |
|
CN |
|
|
Family ID: |
1000005370720 |
Appl. No.: |
17/160003 |
Filed: |
January 27, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16657651 |
Oct 18, 2019 |
10948548 |
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17160003 |
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PCT/CN2017/087564 |
Jun 8, 2017 |
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16657651 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 10/48 20130101;
G01R 31/392 20190101; G01R 31/388 20190101; G01R 31/3648
20130101 |
International
Class: |
G01R 31/392 20060101
G01R031/392; G01R 31/388 20060101 G01R031/388; G01R 31/36 20060101
G01R031/36; H01M 10/48 20060101 H01M010/48 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 18, 2017 |
CN |
201710254759.6 |
Claims
1. A method of estimating a state of health (SOH) of a battery,
comprising: obtaining a partial charge or discharge capacity of the
battery in each of a plurality of state of charge (SOC) ranges;
determining, based on the partial charge or discharge capacity of
the battery in each SOC range of the plurality of SOC ranges, an
overall dV/dSOC data deviation corresponding to each of M preset
battery capacities of the battery to obtain overall dV/dSOC data
deviations corresponding to the M preset battery capacities, where
M is a positive integer; and estimating the SOH of the battery
based on a preset battery capacity corresponding to a smallest
overall dV/dSOC data deviation in the overall dV/dSOC data
deviations.
2. The method according to claim 1, wherein the obtaining the
partial charge or discharge capacity of the battery in each of the
plurality of SOC ranges, comprises: obtaining the partial charge or
discharge capacity of the battery in a first SOC range based on a
coulombic efficiency of the battery, and a random current between a
start moment of the first SOC range and an end moment of the first
SOC range, where the first SOC range is one of the plurality of SOC
ranges.
3. The method according to claim 1, wherein each of the plurality
of SOC ranges starts with an SOC of a plurality of SOCs.
4. The method according to claim 1, wherein the determining an
overall dV/dSOC data deviation corresponding to each of M preset
battery capacities, comprises: obtaining, based on a first preset
battery capacity and the partial charge or discharge capacity of
the battery in each of the plurality of SOC ranges, a first dV/dSOC
data, where the first preset battery capacity is one of the M
preset battery capacities; obtaining, based on a dV/dSOC
characteristic function and the first dV/dSOC data, a second
dV/dSOC data; and obtaining the overall dV/dSOC data deviation
corresponding to the first preset battery capacity based on the
first dV/dSOC data and the second dV/dSOC data.
5. The method according to claim 1, wherein the estimating the SOH
of the battery based on a preset battery capacity corresponding to
a smallest overall dV/dSOC data deviation in the overall dV/dSOC
data deviations corresponding to the M preset battery capacities,
comprises: determining the preset battery capacity corresponding to
the smallest overall dV/dSOC data deviation as a retention capacity
of the battery in an aged state; and determining the SOH of the
battery based on the retention capacity of the battery in the aged
state and a retention capacity of the battery in a new battery
state.
6. An apparatus, comprising a processor; and a memory configured to
store a computer execution instructions, wherein the processor is
configured execute the computer execution instructions to carry out
the following: obtaining a partial charge or discharge capacity of
a battery in each of a plurality of state of charge (SOC) ranges;
determining, based on the partial charge or discharge capacity of
the battery in each SOC range, an overall dV/dSOC data deviation
corresponding to each of M preset battery capacities of the battery
to obtain overall dV/dSOC data deviations corresponding to the M
preset battery capacities, where M is a positive integer; and
estimating the SOH of the battery based on a preset battery
capacity corresponding to a smallest overall dV/dSOC data deviation
in the overall dV/dSOC data deviations.
7. The apparatus according to claim 6, wherein the obtaining the
partial charge or discharge capacity of the battery in each of the
plurality of SOC ranges, comprises: obtaining the partial charge or
discharge capacity of the battery in a first SOC range based on a
coulombic efficiency of the battery, and a random current between a
start moment of the first SOC range and an end moment of the first
SOC rang, where the first SOC range is one of the plurality of SOC
ranges.
8. The apparatus according to claim 6, wherein each of the
plurality of SOC ranges starts with an SOC of a plurality of
SOCs.
9. The apparatus according to claim 6, wherein the determining an
overall dV/dSOC data deviation corresponding to each of M preset
battery capacities, comprises: obtaining, based on a first preset
battery capacity and the partial charge or discharge capacity of
the battery in each of the plurality of SOC ranges, a first dV/dSOC
data, where the first preset battery capacity is one of the M
preset battery capacities; obtaining, based on a dV/dSOC
characteristic function and the first dV/dSOC data, a second
dV/dSOC data; and obtaining the overall dV/dSOC data deviation
corresponding to the first preset battery capacity based on the
first dV/dSOC data and the second dV/dSOC data.
10. The apparatus according to claim 6, wherein the estimating the
SOH of the battery based on a preset battery capacity corresponding
to a smallest overall dV/dSOC data deviation in the overall dV/dSOC
data deviations corresponding to the M preset battery capacities,
comprises: determining the preset battery capacity corresponding to
the smallest overall dV/dSOC data deviation as a retention capacity
of the battery in an aged state; and determining the SOH of the
battery based on the retention capacity of the battery in the aged
state and a retention capacity of the battery in a new battery
state.
11. A non-transitory computer-readable storage medium, comprising a
program, wherein the program is configured to be executed by a
processor to carry out the following: obtaining a partial charge or
discharge capacity of a battery in each of a plurality of state of
charge (SOC) ranges; determining, based on the partial charge or
discharge capacity of the battery in each SOC range, an overall
dV/dSOC data deviation corresponding to each of M preset battery
capacities of the battery to obtain overall dV/dSOC data deviations
corresponding to the M preset battery capacities, where M is a
positive integer; and estimating the SOH of the battery based on a
preset battery capacity corresponding to a smallest overall dV/dSOC
data deviation in the overall dV/dSOC data deviations.
12. The non-transitory computer-readable storage medium according
to claim 11, wherein the obtaining the partial charge or discharge
capacity of the battery in each of the plurality of SOC ranges,
comprises: obtaining the partial charge or discharge capacity of
the battery in a first SOC range based on a coulombic efficiency of
the battery, and a random current between a start moment of the
first SOC range and an end moment of the first SOC range, where the
first SOC range is one of the plurality of SOC ranges.
13. The non-transitory computer-readable storage medium according
to claim 11, wherein each of the plurality of SOC ranges starts
with an SOC of a plurality of SOCs.
14. The non-transitory computer-readable storage medium according
to claim 11, wherein the determining an overall dV/dSOC data
deviation corresponding to each of M preset battery capacities,
comprises: obtaining, based on a first preset battery capacity and
the partial charge or discharge capacity of the battery in each of
the plurality of SOC ranges, a first dV/dSOC data, where the first
preset battery capacity is one of the M preset battery capacities;
obtaining, based on a dV/dSOC characteristic function and the first
dV/dSOC data, a second dV/dSOC data; and obtaining the overall
dV/dSOC data deviation corresponding to the first preset battery
capacity based on the first dV/dSOC data and the second dV/dSOC
data.
15. The non-transitory computer-readable storage medium according
to claim 11, wherein the estimating the SOH of the battery based on
a preset battery capacity corresponding to a smallest overall
dV/dSOC data deviation in the overall dV/dSOC data deviations
corresponding to the M preset battery capacities, comprises:
determining the preset battery capacity corresponding to the
smallest overall dV/dSOC data deviation as a retention capacity of
the battery in an aged state; and determining the SOH of the
battery based on the retention capacity of the battery in the aged
state and a retention capacity of the battery in a new battery
state.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 16/657,651, filed on Oct. 18, 2019, which is a
continuation of International Patent Application No.
PCT/CN2017/087564, filed on Jun. 8, 2017, which claims priority to
Chinese Patent Application No. 201710254759.6, filed on Apr. 18,
2017. The disclosures of the aforementioned applications are hereby
incorporated by reference in their entireties.
TECHNICAL FIELD
[0002] This application relates to the field of battery management
technologies, and in particular, to a method and an apparatus for
estimating a battery state of health (SOH).
BACKGROUND
[0003] With development of society, batteries are more widely used
in various mobile or fixed devices, such as electric vehicles. A
battery SOH is an important parameter for evaluating a battery
management system. Therefore, how to estimate the battery SOH
becomes a hot topic researched in industry.
[0004] In some current methods for estimating a battery SOH, a
percentage of a retention capacity of an aged battery in a capacity
of a battery in anew battery state is defined as a battery SOH.
When the retention capacity of the aged battery is determined, the
parameter usually can be obtained only by performing one full
charge or full discharge test. However, in consideration of safe
usage, the battery usually cannot be fully charged/fully
discharged. In addition, due to a difference between individuals in
a battery pack, it is more unable to ensure that all batteries are
fully charged/fully discharged. Therefore, it is difficult to
evaluate the battery SOH because the foregoing implementation
condition for determining the retention capacity of the aged
battery is relatively harsh.
SUMMARY
[0005] Embodiments of this application provide a method and an
apparatus for estimating a battery SOH, to resolve a current
problem that during evaluation of a battery SOH, it is difficult to
evaluate the battery SOH because a retention capacity of an aged
battery needs to be determined based on full charging/full
discharging of a battery.
[0006] To achieve the foregoing objective, the embodiments of this
application provide the following technical solutions:
[0007] According to a first aspect, an embodiment of this
application provides a method for estimating a battery state of
health (SOH). The method includes: obtaining a partial charge or
discharge capacity of a target battery in a state of charge (SOC)
interval of each of a plurality of states of charge (SOCs), where
the SOC interval of each SOC is an interval whose start SOC is the
SOC and whose length is dSOC; when determining that there are M
preset battery capacities, separately calculating, according to
steps S1 to S3, an overall dV/dSOC data deviation corresponding to
each preset battery capacity, where M is a positive integer: S1.
separately calculating first dV/dSOC data of each SOC in an
m.sup.th preset battery capacity based on the m.sup.th preset
battery capacity and the partial charge or discharge capacity in
the SOC interval of each SOC, where m is a positive integer less
than or equal to M; S2. separately calculating, based on a
prestored dV/dSOC characteristic function, second dV/dSOC data
corresponding to each SOC, where the dV/dSOC characteristic
function is obtained by charging or discharging the target battery
based on a preset current in a new battery state, the preset
current is not greater than 1/20 Q.sub.BOL, and Q.sub.BOL indicates
a retention capacity of the target battery in the new battery
state; and S3. calculating an m.sup.th overall dV/dSOC data
deviation of the plurality of SOCs based on the first dV/dSOC data
of each SOC in the m.sup.th preset battery capacity and the second
dV/dSOC data corresponding to each SOC; determining a smallest
overall dV/dSOC data deviation from all overall dV/dSOC data
deviations; determining a preset battery capacity corresponding to
the smallest overall dV/dSOC data deviation as a retention capacity
of an aged target battery; and dividing the retention capacity of
the aged target battery by the retention capacity of the target
battery in the new battery state, to obtain an SOH of the target
battery. In other words, in this solution, the retention capacity
of the aged target battery is estimated based on the partial charge
or discharge capacity in the SOC interval of each SOC. In this way,
this solution is unlike the prior art in which the parameter can be
obtained only by performing one full charge or full discharge test,
and therefore an implementation condition of this solution is
simpler and more flexible. In addition, this solution does not need
to rely on historical data, and therefore is more robust.
[0008] In a possible design, the obtaining a partial charge or
discharge capacity of a target battery in a SOC interval of each of
a plurality of SOCs includes: obtaining the partial charge or
discharge capacity of the target battery in the SOC interval of
each of the plurality of SOCs with reference to the following first
preset formula, where the first preset formula includes:
[0009]
q.sub.SOC.sub.n=.eta..intg..sub.SOC.sub.n.sub.-t.sub.start.sup.SOC.-
sup.n.sup.-t.sup.endi(t)SOC.sub.ndt, where SOC.sub.n, represents an
n.sup.th SOC, q.sub.SOC.sub.n represents a partial charge or
discharge capacity in a SOC interval of SOC.sub.n, .eta. is
coulombic efficiency of the target battery,
0.ltoreq..eta..ltoreq.1, SOC.sub.n-t.sub.start, represents a start
moment of the SOC interval of SOC.sub.n, SOC.sub.n-t.sub.end
represents an end moment of the SOC interval of SOC.sub.n, and
i(t).sub.SOC.sub.n represents a random current in the SOC interval
of SOC.sub.n. Based on this solution, the partial charge or
discharge capacity of the target battery in the SOC interval of
each of the plurality of SOCs can be obtained.
[0010] In a possible design, the separately calculating first
dV/dSOC data of each SOC in an m.sup.th preset battery capacity
based on the m.sup.th preset battery capacity and the partial
charge or discharge capacity in the SOC interval of each SOC
includes: separately calculating the first dV/dSOC data of each SOC
in the m.sup.th preset battery capacity based on the m.sup.th
preset battery capacity and the partial charge or discharge
capacity in the SOC interval of each SOC and with reference to a
second preset formula, where the second preset formula
includes:
g 1 ( SOC n ) = Q m ( dV dq ) SOC n , ##EQU00001##
where Q.sub.m represents the m.sup.th preset battery capacity,
SOC.sub.n represents the n.sup.th SOC, g.sub.1(SOC.sub.n)
represents first dV/dSOC data of SOC.sub.n in the m.sup.th preset
battery capacity, V represents a voltage, q represents a partial
charge or discharge capacity, and
( dV dq ) SOC n ##EQU00002##
represents
dV dq ##EQU00003##
corresponding to SOC.sub.n. Based on this solution, the first
dV/dSOC data of each SOC in the m.sup.th preset battery capacity
can be calculated.
[0011] In a possible design, when the target battery works in a
discharge state, after the target battery is stable and static for
a period of time, or a working condition of the target battery
keeps at a very small current for a period of time, it can be
considered that battery polarization disappears. In this case, a
terminal voltage (V) of the target battery at an initial moment can
be considered as an open circuit voltage (OCV) of the target
battery at the initial moment. In addition, because an OCV-SOC
curve is linear in a short period of time, it can be learned that
dq is proportional to dOCV in a short period of time. Therefore,
when the target battery works in the discharge state, the second
preset formula specifically includes:
g 1 ( SOC n ) = Q m ( dV dq ) SOC n = Q m OCV SOC n - t end - OCV
SOC n - t start q SOC n ' , ##EQU00004##
where SOC.sub.n-t.sub.start represents the start moment of the SOC
interval of SOC.sub.n, SOC.sub.n-t.sub.end represents the end
moment of the SOC interval of SOC.sub.n,
OCV.sub.SOC.sub.n.sub.-t.sub.end represents an OCV at
SOC.sub.n-t.sub.start, OCV.sub.SOC.sub.n.sub.-t.sub.start
represents an OCV at SOC.sub.n-t.sub.end, and q'.sub.SOC.sub.n
represents a partial discharge capacity in the SOC interval of
SOC.sub.n.
[0012] In a possible design, the dV/dSOC characteristic function
includes:
g 0 ( SOC n ) = a 0 + j = 1 6 ( a j * sin ( j * .omega. * SOC n ) +
b j * cos ( j * .omega. * SOC n ) ) , ##EQU00005##
where SOC.sub.n represents the n.sup.th SOC, SOC.sub.n is an
independent variable of the dV/dSOC characteristic function,
g.sub.0(SOC.sub.n) represents second dV/dSOC data corresponding to
SOC.sub.n, j represents an order, a.sub.0, a.sub.j, and b.sub.j are
coefficients of terms, sin( ) represents a sine function, cos( )
represents a cosine function, and co represents frequency. The
dV/dSOC characteristic function provided in this solution is a
six-order Fourier function. To be specific, in this embodiment of
this application, when the dV/dSOC characteristic function is
fitted by using a fitting tool, the fitting is performed on a basis
that the characteristic function is the six-order Fourier function.
Certainly, in practice, the characteristic function may further
include but is not limited only to a polynomial function, a Fourier
function, an exponential function, and the like. This is not
specifically limited in this embodiment of this application.
[0013] In a possible design, the calculating an m.sup.th overall
dV/dSOC data deviation of the plurality of SOCs based on the first
dV/dSOC data of each SOC in the m.sup.th preset battery capacity
and the second dV/dSOC data corresponding to each SOC includes:
calculating the m.sup.th overall dV/dSOC data deviation of the
plurality of SOCs based on the first dV/dSOC data of each SOC in
the m.sup.th preset battery capacity and the second dV/dSOC data
corresponding to each SOC and with reference to a third preset
formula, where the third preset formula includes:
G m = n = 1 N ( g 0 ( SOC n ) - g 1 ( SOC n ) ) 2 ,
##EQU00006##
where N represents a quantity of SOCs, N is a positive integer not
less than 2, SOC.sub.n represents the n.sup.th SOC,
g.sub.0(SOC.sub.n) represents the second dV/dSOC data corresponding
to SOC.sub.n, g.sub.1(SOC.sub.n) represents the first dV/dSOC data
of SOC.sub.n in the m.sup.th preset battery capacity, and G.sub.m
represents the m.sup.th overall dV/dSOC data deviation of the
plurality of SOCs. Based on this solution, the m.sup.th overall
dV/dSOC data deviation of the plurality of SOCs can be
calculated.
[0014] According to a second aspect, an embodiment of this
application provides an apparatus for estimating a battery SOH. The
apparatus for estimating a battery SOH has a function of
implementing behavior in the foregoing method embodiment. The
function may be implemented by hardware, or may be implemented by
hardware by executing corresponding software. The hardware or the
software includes one or more modules corresponding to the
foregoing function.
[0015] According to a third aspect, an embodiment of this
application provides an apparatus for estimating a battery SOH,
including a processor, a memory, a bus, and a communications
interface. The memory is configured to store a computer execution
instruction. The processor is connected to the memory by using the
bus. When the apparatus for estimating a battery SOH runs, the
processor executes the computer execution instruction stored in the
memory, so that the apparatus for estimating a battery SOH performs
the method for estimating a battery SOH in any possible design of
the first aspect.
[0016] According to a fourth aspect, an embodiment of this
application provides a computer-readable storage medium, configured
to store a computer software instruction used by the foregoing
apparatus for estimating a battery SOH. When the computer software
instruction runs on a computer, the computer can perform the method
for estimating a battery SOH in any possible design of the first
aspect.
[0017] According to a fifth aspect, an embodiment of this
application provides a computer program product that includes an
instruction. When the computer program product runs on a computer,
the computer can perform the method for estimating a battery SOH in
any possible design of the first aspect.
[0018] For technical effects brought by any design manner of the
second to the fourth aspects, refer to technical effects brought by
different design manners of the first aspect, and details are not
described herein again.
[0019] According to a sixth aspect, an embodiment of this
application discloses a method for estimating a battery state of
health (SOH). The method includes:
[0020] obtaining N states of charge (SOCs) of a target battery in N
states, where the SOC is a ratio of a remaining capacity of the
target battery to a full charge capacity of the target battery;
separately calculating first dV/dSOC data of each SOC in an
n.sup.th state of charge based on a charge/discharge capacity of
the target battery in the n.sup.th SOC and an M.sup.th preset
capacity of the battery, where N represents a quantity of SOCs, N
is a positive integer not less than 2, n is a positive integer less
than or equal to N, m is a positive integer from 1 to M, and M is a
quantity of preset capacities; separately calculating, based on a
dV/dSOC-SOC characteristic function, second dV/dSOC data
corresponding to each SOC, where the dV/dSOC-SOC characteristic
function is obtained by charging or discharging the target battery
based on a preset current in an new battery state, the preset
current is not greater than 1/20 Q.sub.BOL, and Q.sub.BOL indicates
a retention capacity of the target battery in the new battery
state; obtaining an m.sup.th overall dV/dSOC data deviation of the
plurality of SOCs through calculation based on the first dV/dSOC
data of each SOC in the m.sup.th preset battery capacity and the
second dV/dSOC data corresponding to each SOC; determining a
smallest overall dV/dSOC data deviation from M overall dV/dSOC data
deviations; determining a preset battery capacity corresponding to
the smallest overall dV/dSOC data deviation as a retention capacity
of an aged target battery; and obtaining an SOH of the target
battery through calculation based on the retention capacity of the
aged target battery. In this way, this solution is unlike the prior
art in which the parameter can be obtained only by performing one
full charge or full discharge test, and therefore an implementation
condition of this solution is simpler and more flexible. In
addition, this solution does not need to rely on historical data,
and therefore is more robust.
[0021] With reference to the sixth aspect, it should be noted that
the obtaining an SOH of the target battery through calculation
based on the retention capacity of the aged target battery
includes: dividing the retention capacity of the aged target
battery by the retention capacity of the target battery in the new
battery state, to obtain the SOH of the target battery.
[0022] With reference to the sixth aspect, in a possible design,
the method further includes: obtaining a partial charge or
discharge capacity of the target battery in a SOC interval of each
SOC in the n.sup.th SOC, where the SOC interval of each SOC is an
interval whose start SOC is the SOC and whose length is dSOC, and
the charge/discharge capacity in the n.sup.th SOC is a partial
charge or discharge capacity in the interval.
[0023] Specifically, the obtaining a partial charge or discharge
capacity of the target battery in a SOC interval of each SOC in the
n.sup.th SOC includes:
[0024] obtaining the partial charge or discharge capacity of the
target battery in the SOC interval of each of the plurality of SOCs
with reference to the following first preset formula, where the
first preset formula includes:
[0025]
q.sub.SOC.sub.n=.eta..intg..sub.SOC.sub.n.sub.-t.sub.start.sup.SOC.-
sup.n.sup.-t.sup.endi(t)SOC.sub.ndt, where SOC.sub.n represents the
n.sup.th SOC, q.sub.SOC.sub.n represents a partial charge or
discharge capacity in a SOC interval of SOC.sub.n, .eta. is
coulombic efficiency of the target battery,
0.ltoreq..eta..ltoreq.1, SOC.sub.n-t.sub.start represents a start
moment of the SOC interval of SOC.sub.n, SOC.sub.n-t.sub.end
represents an end moment of the SOC interval of SOC.sub.n, and
i(t)SOC.sub.n represents a random current in the SOC interval of
SOC.sub.n.
[0026] With reference to the sixth aspect, the separately
calculating first dV/dSOC data of each SOC in an n.sup.th state of
charge based on a charge/discharge capacity of the target battery
in the n.sup.th SOC and an m.sup.th preset capacity of the battery
includes:
[0027] separately calculating the first dV/dSOC data of each SOC in
the m.sup.th preset battery capacity based on the m.sup.th preset
battery capacity and the partial charge or discharge capacity in
the SOC interval of each SOC and with reference to a second preset
formula, where the second preset formula includes:
g 1 ( SOC n ) = Q m ( dV dq ) SOC n , ##EQU00007##
where Q.sub.m represents the m.sup.th preset battery capacity,
SOC.sub.n represents the n.sup.th SOC, g.sub.1(SOC.sub.n)
represents first dV/dSOC data of SOC.sub.n in the m.sup.th preset
battery capacity, V represents a voltage, q represents a partial
charge or discharge capacity, and
( dV dq ) SOC n ##EQU00008##
represents
d V d q ##EQU00009##
corresponding to SOC.sub.n.
[0028] When the target battery works in a discharge state, the
second preset formula specifically includes:
g 1 ( SOC n ) = Q m ( dV dq ) SOC n = Q m OCV SOC n - t end - OCV
SOC n - t start q SOC n ' , ##EQU00010##
where SOC.sub.n-t.sub.start represents the start moment of the SOC
interval of SOC.sub.n, SOC.sub.n-t.sub.end represents the end
moment of the SOC interval of SOC.sub.n,
OCV.sub.SOC.sub.n.sub.-t.sub.end represents an OCV at
SOC.sub.n-t.sub.start, OCV.sub.SOC.sub.n.sub.-t.sub.start
represents an OCV at SOC.sub.n-t.sub.end, and q'.sub.SOC represents
a partial discharge capacity in the SOC interval of SOC.sub.n.
[0029] In addition, it should be noted that the dV/dSOC-SOC
characteristic function includes:
g 0 ( SOC n ) = a 0 + j = 1 6 ( a j * sin ( j * .omega. * SOC n ) +
b j * cos ( j * .omega. * SOC n ) ) , ##EQU00011##
where SOC.sub.n represents the n.sup.th SOC.sub.n is an independent
variable of the dV/dSOC-SOC characteristic function,
g.sub.0(SOC.sub.n) represents second dV/dSOC data corresponding to
SOC.sub.n, j represents an order, a.sub.0, a.sub.j, and b.sub.j are
coefficients of terms, sin( ) represents a sine function, cos( )
represents a cosine function, and co represents frequency.
[0030] With reference to the sixth aspect, it should be noted that
the calculating an m.sup.th overall dV/dSOC data deviation of the
plurality of SOCs based on the first dV/dSOC data of each SOC in
the m.sup.th preset battery capacity and the second dV/dSOC data
corresponding to each SOC includes:
[0031] calculating the m.sup.th overall dV/dSOC data deviation of
the plurality of SOCs based on the first dV/dSOC data of each SOC
in the m.sup.th preset battery capacity and the second dV/dSOC data
corresponding to each SOC and with reference to a third preset
formula, where the third preset formula includes:
G m = n = 1 N ( g 0 ( SOC n ) - g 1 ( SOC n ) ) 2 ,
##EQU00012##
[0032] where N represents the quantity of SOCs, N is a positive
integer not less than 2, SOC.sub.n represents the n.sup.th SOC,
g.sub.0(SOC) represents the second dV/dSOC data corresponding to
SOC.sub.n, g.sub.1(SOC.sub.n) represents the first dV/dSOC data of
SOC.sub.n in the m.sup.th preset battery capacity, and G.sub.m
represents the m.sup.th overall dV/dSOC data deviation of the
plurality of SOCs.
[0033] According to a seventh aspect, an embodiment of the present
invention discloses an apparatus for estimating a battery state of
health (SOH). The apparatus includes an obtaining module and a
calculation module, where the obtaining module obtains N states of
charge (SOCs) of a target battery in N states, where the SOC is a
ratio of a remaining capacity of the target battery to a full
charge capacity of the target battery; and the calculation module
is configured to: separately calculate first dV/dSOC data of each
SOC in an n.sup.th state of charge based on a charge/discharge
capacity of the target battery in the n.sup.th SOC and an m.sup.th
preset capacity of the battery, where N represents a quantity of
SOCs, N is a positive integer not less than 2, n is a positive
integer less than or equal to N, m is a positive integer from 1 to
M, and M is a quantity of preset capacities;
[0034] separately calculate, based on a dV/dSOC-SOC characteristic
function, second dV/dSOC data corresponding to each SOC, where the
dV/dSOC-SOC characteristic function is obtained by charging or
discharging the target battery based on a preset current in an new
battery state, the preset current is not greater than 1/20
Q.sub.BOL, and Q.sub.BOL indicates a retention capacity of the
target battery in the new battery state;
[0035] obtain an m.sup.th overall dV/dSOC data deviation of the
plurality of SOCs through calculation based on the first dV/dSOC
data of each SOC in the m.sup.th preset battery capacity and the
second dV/dSOC data corresponding to each SOC;
[0036] determine a smallest overall dV/dSOC data deviation from M
overall dV/dSOC data deviations;
[0037] determine a preset battery capacity corresponding to the
smallest overall dV/dSOC data deviation as a retention capacity of
an aged target battery; and
[0038] obtain an SOH of the target battery through calculation
based on the retention capacity of the aged target battery.
[0039] Optionally, the calculation module is specifically
configured to divide the retention capacity of the aged target
battery by the retention capacity of the target battery in the new
battery state, to obtain the SOH of the target battery.
[0040] With reference to the seventh aspect, the obtaining module
is further configured to obtain a partial charge or discharge
capacity of the target battery in a SOC interval of each SOC in the
n.sup.th SOC, where the SOC interval of each SOC is an interval
whose start SOC is the SOC and whose length is dSOC, and the
charge/discharge capacity in the n.sup.th SOC is a partial charge
or discharge capacity in the interval.
[0041] With reference to the seventh aspect, optionally, the
obtaining module is specifically configured to:
[0042] obtain the partial charge or discharge capacity of the
target battery in the SOC interval of each of the plurality of SOCs
with reference to the following first preset formula, where the
first preset formula includes:
[0043]
q.sub.SOC.sub.n=.eta..intg..sub.SOC.sub.n.sub.-t.sub.start.sup.SOC.-
sup.n.sup.-t.sup.endi(t)SOC.sub.ndt, where SOC.sub.n, represents
the n.sup.th SOC, q.sub.SOC.sub.n represents a partial charge or
discharge capacity in a SOC interval of SOC.sub.n, .eta. is
coulombic efficiency of the target battery,
0.ltoreq..eta..ltoreq.1, SOC.sub.n-t.sub.start represents a start
moment of the SOC interval of SOC.sub.n, SOC.sub.n-t.sub.end
represents an end moment of the SOC interval of SOC.sub.n, and
i(t).sub.SOC.sub.n represents a random current in the SOC interval
of SOC.sub.n.
[0044] With reference to the seventh aspect, optionally, the
calculation module is specifically configured to:
[0045] separately calculate the first dV/dSOC data of each SOC in
the m.sup.th preset battery capacity based on the m.sup.th preset
battery capacity and the partial charge or discharge capacity in
the SOC interval of each SOC and with reference to a second preset
formula, where the second preset formula includes:
g 1 ( SOC n ) = Q m ( dV dq ) SOC n , ##EQU00013##
where Q.sub.m represents the m.sup.th preset battery capacity,
SOC.sub.n represents the n.sup.th SOC, g.sub.1(SOC.sub.n)
represents first dV/dSOC data of SOC.sub.n in the m.sup.th preset
battery capacity, V represents a voltage, q represents a partial
charge or discharge capacity, and
( dV d q ) SOC n ##EQU00014##
represents
d V d q ##EQU00015##
corresponding to SOC.sub.n.
[0046] It should be noted that, when the target battery works in a
discharge state, the second preset formula specifically
includes:
g 1 ( SOC n ) = Q m ( d V d q ) SOC n = Q m O C V SOC n - t end - O
C V SOC n - t start q SOC n ' , ##EQU00016##
where SOC.sub.n-t.sub.start represents the start moment of the SOC
interval of SOC.sub.n, SOC.sub.n-t.sub.end represents the end
moment of the SOC interval of SOC.sub.n,
OCV.sub.SOC.sub.n.sub.-t.sub.end, represents an OCV at
SOC.sub.n-t.sub.start, OCV.sub.SOC.sub.n.sub.-t.sub.start
represents an OCV at SOC.sub.n-t.sub.end, and q'.sub.SOC.sub.n
represents a partial discharge capacity in the SOC interval of
SOC.sub.n.
[0047] With reference to the seventh aspect, it should be noted
that the dV/dSOC-SOC characteristic function includes:
g 0 ( SOC n ) = a 0 + j = 1 6 ( a j * sin ( j * .omega. * S O C n )
+ b j * cos ( j * .omega. * S O C n ) ) , ##EQU00017##
where SOC.sub.n represents the n.sup.th SOC, SOC.sub.n is an
independent variable of the dV/dSOC-SOC characteristic function,
g.sub.0(SOC.sub.n) represents second dV/dSOC data corresponding to
SOC.sub.n, j represents an order, a.sub.0, a.sub.j, and b.sub.j are
coefficients of terms, sin( ) represents a sine function, cos( )
represents a cosine function, and co represents frequency.
[0048] With reference to the seventh aspect, optionally, the
calculation module is specifically configured to:
[0049] calculate the m.sup.th overall dV/dSOC data deviation of the
plurality of SOCs based on the first dV/dSOC data of each SOC in
the m.sup.th preset battery capacity and the second dV/dSOC data
corresponding to each SOC and with reference to a third preset
formula, where the third preset formula includes:
G m = n = 1 N ( g 0 ( SO C n ) - g 1 ( SO C n ) ) 2 ,
##EQU00018##
where N represents the quantity of SOCs, N is a positive integer
not less than 2, SOC.sub.n represents the n.sup.th SOC,
g.sub.0(SOC) represents the second dV/dSOC data corresponding to
SOC.sub.n, g.sub.1(SOC.sub.n) represents the first dV/dSOC data of
SOC.sub.n in the m.sup.th preset battery capacity, and G.sub.m
represents the m.sup.th overall dV/dSOC data deviation of the
plurality of SOCs.
[0050] According to an eighth aspect, an embodiment of this
application discloses an apparatus for estimating a battery SOH,
including a processor, a memory, a bus, and a communications
interface. The memory is configured to store a computer execution
instruction. The processor is connected to the memory by using the
bus. When the apparatus runs, the processor executes the computer
execution instruction stored in the memory, so that the apparatus
performs the method for estimating a battery SOH in the sixth
aspect.
[0051] According to a ninth aspect, an embodiment of this
application provides a computer-readable storage medium, configured
to store a computer software instruction used by the foregoing
apparatus for estimating a battery SOH. When the computer software
instruction runs on a computer, the computer can perform the method
for estimating a battery SOH in any possible design of the sixth
aspect.
[0052] According to a tenth aspect, an embodiment of this
application provides a computer program product that includes an
instruction. When the computer program product runs on a computer,
the computer can perform the method for estimating a battery SOH in
any possible design of the sixth aspect.
[0053] These aspects or other aspects of this application are
clearer and more comprehensible in descriptions of the following
embodiments.
BRIEF DESCRIPTION OF DRAWINGS
[0054] FIG. 1 is a schematic architectural diagram of a system for
estimating a battery SOH according to an embodiment of this
application;
[0055] FIG. 2 is a schematic diagram of a hardware structure of an
apparatus for estimating a battery SOH according to an embodiment
of this application;
[0056] FIG. 3 is a schematic flowchart of a method for estimating a
battery SOH according to an embodiment of this application;
[0057] FIG. 4 is a voltage-capacity line graph of charging or
discharging a target battery based on a preset current in a new
battery state and at different aging degrees according to an
embodiment of this application;
[0058] FIG. 5 is a V-SOC line graph, corresponding to FIG. 4, of
charging or discharging a target battery based on a preset current
in a new battery state and at different aging degrees according to
an embodiment of this application;
[0059] FIG. 6 shows dV/dSOC characteristic curves of charging or
discharging a target battery based on a preset current in a new
battery state and at different aging degrees according to an
embodiment of this application;
[0060] FIG. 7 is a schematic diagram of comparing a fitted curve
with an actual curve according to an embodiment of this
application;
[0061] FIG. 8 is a schematic structural diagram of an apparatus for
estimating a battery SOH according to an embodiment of this
application; and
[0062] FIG. 9 is a schematic structural diagram of another
apparatus for estimating a battery SOH according to an embodiment
of this application.
DESCRIPTION OF EMBODIMENTS
[0063] To facilitate understanding of the technical solutions in
the embodiments of this application, explanations of several key
terms are first provided as follows:
[0064] Retention capacity: a full charge or discharge capacity that
is of a battery and that is obtained after the battery is used for
a period of time or left unused for a long period of time.
[0065] Aging: a phenomenon that a battery capacity naturally
attenuates when a battery is used for a period of time or left
unused for a long period of time. Specifically, aging of a battery
generally includes two parts: aging in a cycle process (namely, a
cycle life), and aging in a process in which the battery is left
unused (namely, a calendar life). The aging in the cycle process
means that as a quantity of times of charging/discharging the
battery increases, an available quantity of times that the battery
can be charged/discharged decreases correspondingly, where a total
quantity of times of charging/discharging the battery is measurable
and can be estimated; and a retention capacity during each time of
charging/discharging attenuates. The aging in the process in which
the battery is left unused means that when the battery is not
charged/discharged, a retention capacity of the battery attenuates
with time. A form of the aging in the embodiments of this
application is not limited. Uniform description is provided herein,
and details are not described below again.
[0066] A new battery state (beginning of life, BOL) is specifically
a battery state in which a retention capacity is 100%.
[0067] State of health (SOH): a percentage of a retention capacity
of an aged battery in a capacity of a battery in a new battery
state is defined as a battery SOH.
[0068] State of charge (SOC): the SOC is a ratio of a remaining
capacity of a battery to a full charge capacity of the battery, and
is usually expressed as a percentage.
[0069] Open circuit voltage (OCV): a terminal voltage of a battery
in an open circuit state is referred to as the open circuit
voltage.
[0070] Battery polarization: a phenomenon that an actual electrode
potential deviates from a balanced electrode potential after a
static state is broken due to current flow.
[0071] The following describes the technical solutions in the
embodiments of this application with reference to the accompanying
drawings in the embodiments of this application. In the
descriptions of this application, unless otherwise stated, "I"
indicates "or", for example, A/B may indicate A or B; and "and/or"
in this specification describes merely an association relationship
for describing associated objects, and indicates that three
relationships may exist. For example, A and/or B may indicate the
following three cases: Only A exists, both A and B exist, and only
B exists. In addition, in the descriptions of this application, "a
plurality of" means "two or more".
[0072] FIG. 1 shows a system 10 for estimating a battery SOH
according to an embodiment of this application. The system 10 for
estimating a battery SOH includes a battery 20, a battery detection
apparatus 21, a charging/discharging execution apparatus 22, an
absolute-time unit 23, a controller 24, a storage chip 25, and an
apparatus 26 for estimating a battery SOH.
[0073] The battery detection apparatus 21 is configured to upload
data that is detected in real time to the controller. The battery
detection apparatus 21 includes three parts: a battery voltage
sampling component, a current sampling unit, and a temperature
sampling component. The battery voltage sampling component includes
a sampling chip and a connection bundle. The current sampling unit
includes a current sampling chip and a current sensor. The
temperature sampling component includes a temperature sampling chip
and a temperature sensor.
[0074] The charging/discharging execution apparatus 22 is
configured to charge/discharge the battery.
[0075] The absolute-time unit 23 is configured to send, to the
controller 24 in real time, an absolute time provided by a
high-frequency crystal oscillator.
[0076] The controller 24 is configured to: control sampling for the
battery, receive the absolute time, and pack sampled data and the
absolute time and then store the packed sampled data and absolute
time in the storage chip 25; and control a charge/discharge current
and a state of the battery by using the charging/discharging
execution apparatus 22.
[0077] The storage chip 25 is configured to: prestore dV/dSOC-SOC
information of a new battery, and store collected valid battery
data in real time and in a particular format.
[0078] The apparatus 26 for estimating a battery SOH is configured
to: perform an ordered storage and read operation on data in the
storage chip 25, and estimate a battery SOH based on the read data.
For a specific implementation, refer to the following method
embodiment, and details are not described herein.
[0079] The system 10 for estimating a battery SOH may further
include a power supply, a security protection apparatus, an
insulation apparatus, and the like although they are not shown.
This is not specifically limited in this embodiment of this
application.
[0080] FIG. 2 is a schematic diagram of a hardware structure of an
apparatus 26 for estimating a battery SOH according to an
embodiment of this application. The apparatus 26 for estimating a
battery SOH includes at least one processor 2601, a communications
bus 2602, a memory 2603, and at least one communications interface
2604.
[0081] The processor 2601 may be a general-purpose central
processing unit (CPU), a microprocessor, an application-specific
integrated circuit (ASIC), or one or more integrated circuits
configured to control program execution of the solutions in this
application.
[0082] The communications bus 2602 may include a channel for
transmitting information between the foregoing components.
[0083] The communications interface 2604 is configured to use any
apparatus like a transceiver to communicate with another device or
a communications network, such as the Ethernet, a radio access
network (RAN), or a wireless local area network (WLAN).
[0084] The memory 2603 may be a read-only memory (ROM) or another
type of static storage device capable of storing static information
and instructions, or a random access memory (RAM) or another type
of dynamic storage device capable of storing information and
instructions, or may be an electrically erasable programmable
read-only memory (EEPROM), a compact disc read-only memory (CD-ROM)
or another compact disc storage, an optical disc storage (including
a compressed optical disc, a laser disc, an optical disc, a digital
versatile disc, a Blu-ray optical disc, and the like), a magnetic
disk storage medium or another magnetic storage device, or any
other medium capable of carrying or storing expected program code
in a form of an instruction or a data structure and capable of
being accessed by a computer. However, the memory 2603 is not
limited thereto. The memory may exist independently, and is
connected to the processor by using the bus. Alternatively, the
memory may be integrated with the processor.
[0085] The memory 2603 is configured to store application program
code for executing the solutions in this application, and the
processor 2601 controls the execution. The processor 2601 is
configured to execute the application program code stored in the
memory 2603, to implement the method for estimating a battery SOH
that is provided in the embodiments of this application.
[0086] During specific implementation, in an embodiment, the
processor 2601 may include one or more CPUs, for example, a CPU 0
and a CPU 1 in FIG. 2.
[0087] During specific implementation, in an embodiment, the
apparatus 26 for estimating a battery SOH may include a plurality
of processors, for example, the processor 2601 and a processor 2608
in FIG. 2. Each of the processors may be a single-core (single-CPU)
processor, or may be a multi-core (multi-CPU) processor. The
processor herein may be one or more devices, circuits, and/or
processing cores for processing data (e.g., a computer program
instruction).
[0088] During specific implementation, in an embodiment, the
apparatus 26 for estimating a battery SOH may further include an
output device 2605 and an input device 2606. The output device 2605
communicates with the processor 2601, and can display information
in a plurality of manners. For example, the output device 2605 may
be a liquid crystal display (LCD), a light emitting diode (LED)
display device, a cathode-ray tube (CRT) display device, or a
projector. The input device 2606 communicates with the processor
2601, and can receive a user input in a plurality of manners. For
example, the input device 2606 may be a mouse, a keyboard, a
touchscreen device, or a sensing device.
[0089] FIG. 3 shows a method for estimating a battery SOH according
to an embodiment of this application. The method includes the
following steps.
[0090] S301. An apparatus for estimating a battery SOH obtains a
partial charge or discharge capacity of a target battery in a SOC
interval of each of a plurality of SOCs.
[0091] The SOC interval of each SOC is an interval whose start SOC
is the SOC and whose length is dSOC.
[0092] S302. When determining that there are M preset battery
capacities, the apparatus for estimating a battery SOH separately
calculates, according to steps S1 to S3, an overall dV/dSOC data
deviation corresponding to each preset battery capacity, where M is
a positive integer.
[0093] S1. The apparatus for estimating a battery SOH separately
calculates first dV/dSOC data of each SOC in an m.sup.th preset
battery capacity based on the m.sup.th preset battery capacity and
the partial charge or discharge capacity in the SOC interval of
each SOC.
[0094] m is a positive integer less than or equal to M.
[0095] S2. The apparatus for estimating a battery SOH separately
calculates, based on a prestored dV/dSOC characteristic function,
second dV/dSOC data corresponding to each SOC.
[0096] The dV/dSOC characteristic function is obtained by charging
or discharging the target battery based on a preset current in a
new battery state, the preset current is not greater than 1/20
Q.sub.BOL, and Q.sub.BOL indicates a retention capacity of the
target battery in the new battery state.
[0097] S3. The apparatus for estimating a battery SOH calculates an
m.sup.th overall dV/dSOC data deviation of the plurality of SOCs
based on the first dV/dSOC data of each SOC in the m.sup.th preset
battery capacity and the second dV/dSOC data corresponding to each
SOC.
[0098] S303. The apparatus for estimating a battery SOH determines
a smallest overall dV/dSOC data deviation from all overall dV/dSOC
data deviations.
[0099] S304. The apparatus for estimating a battery SOH determines
a preset battery capacity corresponding to the smallest overall
dV/dSOC data deviation as a retention capacity of an aged target
battery.
[0100] S305. The apparatus for estimating a battery SOH divides the
retention capacity of the aged target battery by a retention
capacity of the target battery in a new battery state, to obtain an
SOH of the target battery.
[0101] In step S301:
[0102] The SOC interval of each SOC is an interval whose start SOC
is the SOC and whose length is dSOC. For example, a SOC interval of
a first SOC is an interval whose start SOC is the first SOC and
whose length is dSOC. All SOCs intervals may have same dSOC, or may
have different dSOC. This is not specifically limited in this
embodiment of this application.
[0103] It should be noted that, for ease of representation, in this
embodiment of this application, the first SOC is denoted as
SOC.sub.1, a second SOC is denoted as SOC.sub.2, and an n.sup.th
SOC is denoted as SOC.sub.n. This is uniformly described herein,
and details are not described below again.
[0104] Optionally, the obtaining, by an apparatus for estimating a
battery SOH, a partial charge or discharge capacity of a target
battery in a SOC interval of each of a plurality of SOCs may
specifically include: obtaining, by the apparatus for estimating a
battery SOH, the partial charge or discharge capacity of the target
battery in the SOC interval of each of the plurality of SOCs with
reference to formula (1). Formula (1) is as follows:
q.sub.SOC.sub.n=.eta..intg..sub.SOC.sub.n.sub.-t.sub.start.sup.SOC.sup.n-
.sup.-t.sup.endi(t)SOC.sub.ndt formula (1)
[0105] SOC.sub.n represents the n.sup.th SOC. q.sub.SOC.sub.n
represents a partial charge or discharge capacity in a SOC interval
of SOC.sub.n, .eta. is coulombic efficiency of the target battery,
0.ltoreq..eta..ltoreq.1, and .eta. may be given based on a battery
type. For a lithium-ion battery, .eta. may be 1. For another type
of battery such as a lead-acid battery, a NiMH battery, or a Ni--Cd
battery, .eta. may be a value from 0.9 to 1 based on a different
type. SOC.sub.n-t.sub.start represents a start moment of the SOC
interval of SOC.sub.n. SOC.sub.n-t.sub.end represents an end moment
of the SOC interval of SOC.sub.n. i(t) SOC.sub.n, represents a
random current in the SOC interval of SOC.sub.n.
[0106] For example, when the target battery works in a charge
state, for the SOC interval of each SOC, when a charge current of
the target battery is less than a preset value, for example, when
in a large-current charge process, a current in an initial charge
phase and a current in an end charge phase are controlled to be
less than 1/20 Q.sub.BOL or a current in the entire charge process
is controlled to be less than 1/20 Q.sub.BOL the battery detection
apparatus 21 in FIG. 1 may flush all collected data into the
storage chip 25 in a form of a structure array. The structure
includes several array elements, such as a voltage, a current, a
temperature, an absolute time, and an initial SOC, and may be
specifically represented as Data (k) {V[ ], I[ ], Temp[ ], Time[ ],
SOC[ ]}, where k is a natural number from 0 to K and represents K
pieces of structure data. Recording frequency is recorded based on
sampling frequency, and recording duration is
.DELTA.t=t.sub.end-t.sub.start. Then, the apparatus for estimating
a battery SOH may read the foregoing structure data from the
storage chip 25, and then obtain a partial charge capacity of the
target battery in the SOC interval of each of the plurality of SOCs
with reference to formula (1).
[0107] For example, when the target battery works in a discharge
state, for the SOC interval of each SOC, when the target battery is
in an approximate open-circuit stable state, the battery detection
apparatus 21 in FIG. 1 may flush all collected data into the
storage chip 25 in a form of a structure array. The structure
includes several array elements, such as a voltage, a current, a
temperature, an absolute time, and an initial SOC, and may be
specifically represented as Data (k) {V[ ], I[ ], Temp[ ], Time[ ],
SOC[ ]}, where k is a natural number from 0 to K and represents K
pieces of structure data. Recording frequency is recorded based on
sampling frequency, and recording duration is
.DELTA.t=t.sub.end-t.sub.start. Then, the apparatus for estimating
a battery SOH may read the foregoing structure data from the
storage chip 25, and then obtain a partial discharge capacity of
the target battery in the SOC interval of each of the plurality of
SOCs with reference to formula (1). In this embodiment of this
application, if a current value I of the target battery is greater
than -.beta. and is less than .beta. and this lasts .gamma.
minutes, or the target battery is left unused in an open circuit
for more than 15 minutes, it is considered that the target battery
reaches the approximate open-circuit stable state. Values of .beta.
and .gamma. are determined based on a characteristic of the target
battery. Generally, .beta. is 2 A, and .gamma. is 5 to 10
minutes.
[0108] For example, for SOC.sub.1, the apparatus for estimating a
battery SOH may read K pieces of structure data in a SOC interval
of SOC.sub.1 from the storage chip 25, and obtain a partial charge
or discharge capacity in the SOC interval of SOC.sub.1 according to
formula (1). The partial charge or discharge capacity in the SOC
interval of SOC.sub.1 is as follows:
q SOC 1 = .eta. .intg. S O C 1 - t start S O C 1 - t e n d i ( t )
S O C 1 d t = .eta. k = 0 K I [ k ] S O C 1 ##EQU00019##
[0109] It should be noted that in this embodiment of this
application, a value of K depends on an absolute time t, an
absolute time t.sub.start is an absolute moment at which data is
recorded at the beginning of an algorithm, an absolute time
t.sub.end is an absolute moment at which an SOH starts to be
estimated at the end of the algorithm, and a time difference
between t.sub.start and t.sub.end is usually not more than one
month. In addition, the value of K cannot exceed a preset upper
limit value. For example, the preset upper limit value is 100, and
this indicates that data recording is performed for a maximum of
one hundred times. The preset upper limit value may be determined
based on a size of the storage chip 25. When storage permission is
met, a larger preset upper limit value indicates a larger amount of
data participating in estimation and higher estimation
accuracy.
[0110] In S1 of step S302:
[0111] Optionally, the separately calculating, by the apparatus for
estimating a battery SOH, first dV/dSOC data of each SOC in an
m.sup.th preset battery capacity based on the m.sup.th preset
battery capacity and the partial charge or discharge capacity in
the SOC interval of each SOC may specifically include: separately
calculating, by the apparatus for estimating a battery SOH, the
first dV/dSOC data of each SOC in the m.sup.th preset battery
capacity based on the m.sup.th preset battery capacity and the
partial charge or discharge capacity in the SOC interval of each
SOC and with reference to formula (2). Formula (2) is as
follows:
g 1 ( S O C n ) = Q m ( d V d q ) SOC n formula ( 2 )
##EQU00020##
[0112] Q.sub.m represents the m.sup.th preset battery capacity,
SOC.sub.n represents the n.sup.th SOC, g.sub.1(SOC.sub.n)
represents first dV/dSOC data of SOC.sub.n in the m.sup.th preset
battery capacity, V represents a voltage, q represents a partial
charge or discharge capacity, and
( dV d q ) SOC n ##EQU00021##
represents
d V d q ##EQU00022##
corresponding to SOC.sub.n.
[0113] For example, assuming that the apparatus for estimating a
battery SOH can read K pieces of structure data in the SOC interval
of SOC.sub.n from the storage chip 25, because a V-SOC curve is
linear in a short period of time, the apparatus for estimating a
battery SOH may calculate the first dV/dSOC data of SOC.sub.n in
the m.sup.th preset battery capacity according to formula (2). The
first dV/dSOC data of SOC.sub.n in the m.sup.th preset battery
capacity is as follows:
g 1 ( SOC n ) = Q m ( dV d q ) SOC n = Q m V SOC n - t end - V SOC
n - t start q SOC n = Q m V [ K ] SOC n - V [ 0 ] SOC n q SOC n
##EQU00023##
[0114] SOC.sub.n-t.sub.start represents the start moment of the SOC
interval of SOC.sub.n, SOC.sub.n-t.sub.end represents the end
moment of the SOC interval of SOC.sub.n,
V[K].sub.SOC.sub.n.sub.-t.sub.end represents a voltage at
SOC.sub.n-t.sub.end, V.sub.SOC.sub.n.sub.-t.sub.start represents a
voltage at SOC.sub.n-t.sub.start, V[K].sub.SOC.sub.n represents a
K.sup.th voltage in the SOC interval of SOC.sub.n, and
V[0].sub.SOC.sub.n, represents an initial voltage in the SOC
interval of SOC.sub.n.
[0115] Optionally, when the target battery works in a discharge
state, after the target battery is stable and static for a period
of time, or a working condition of the target battery keeps at a
very small current for a period of time, it can be considered that
battery polarization disappears. In this case, a terminal voltage V
of the target battery at an initial moment can be considered as an
OCV of the target battery at the initial moment. In addition,
because an OCV-SOC curve is linear in a short period of time, it
can be learned that dq is proportional to dOCV in a short period of
time. Therefore, when the target battery works in the discharge
state, the foregoing formula (2) can be evolved into the following
formula (3):
g 1 ( SOC n ) = Q m ( dV d q ) SOC n = Q m OCV SOC n - t end - OCV
SOC n - t start q SOC n ' formula ( 3 ) ##EQU00024##
[0116] OCV.sub.SOC.sub.n.sub.-t.sub.end represents an OCV at
SOC.sub.n-t.sub.start, OCV.sub.SOC.sub.n.sub.-t.sub.start
represents an OCV at SOC.sub.n-t.sub.start, and q'.sub.SOC
represents a partial discharge capacity in the SOC interval of
SOC.sub.n.
[0117] Optionally, the apparatus for estimating a battery SOH may
determine OCV.sub.t and OCV.sub.SOC.sub.n.sub.-t.sub.end based on a
start SOC and an end SOC of the SOC interval of SOC.sub.n and with
reference to a prestored correspondence between a SOC and an OCV.
This is not specifically limited in this embodiment of this
application.
[0118] For example, assuming that the apparatus for estimating a
battery SOH can read the K pieces of structure data in the SOC
interval of SOC.sub.n from the storage chip 25, the apparatus for
estimating a battery SOH may calculate the first dV/dSOC data in
the m.sup.th preset battery capacity according to formula (3). The
first dV/dSOC data in the m.sup.th preset battery capacity is as
follows:
g 1 ( SOC n ) = Q m ( dV dq ) SOC n = Q m ( OCV SOC n - t end - OCV
SOC n - t start q SOC n ' ) m OCV [ K ] SOC n - OCV [ 0 ] SOC n q
SOC n ' ##EQU00025##
[0119] OCV[K].sub.SOC.sub.n represents a K.sup.th OCV in the SOC
interval of SOC.sub.n, and OCV[0].sub.SOC.sub.n represents an
initial OCV in the SOC interval of SOC.sub.n. OCV[K].sub.SOC.sub.n
can be determined based on SOC.sub.n[K] and the prestored
correspondence between a SOC and an OCV, and OCV[0].sub.SOC.sub.n
can be determined based on SOC.sub.n[0] and the prestored
correspondence between a SOC and an OCV. SOC.sub.n[K] represents a
K.sup.th SOC in the SOC interval of SOC.sub.n, and SOC.sub.n[0]
represents an initial SOC in the SOC interval of SOC.sub.n.
[0120] In S2 of step S302:
[0121] That the apparatus for estimating a battery SOH separately
calculates, based on a prestored dV/dSOC characteristic function,
second dV/dSOC data corresponding to each SOC is specifically that
the apparatus for estimating a battery SOH separately substitutes
each SOC to the prestored dV/dSOC characteristic function to obtain
the second dV/dSOC data corresponding to each SOC.
[0122] Optionally, the prestored dV/dSOC characteristic function
may be obtained in the following manner:
[0123] Step 1: Charge or discharge the target battery based on a
preset current in a new battery state, to obtain a voltage-capacity
curve.
[0124] The preset current is not greater than 1/20 Q.sub.BOL. For
example, the preset current is 1/25 Q.sub.BOL.
[0125] For example, FIG. 4 is a voltage-capacity (V-Q) line graph
of charging or discharging the target battery based on the preset
current in the new battery state and at different aging degrees
according to this embodiment of this application. A curve 1 is a
V-Q line graph of charging or discharging the target battery based
on the preset current in the new battery state. A curve 2 is a V-Q
line graph of charging or discharging the target battery based on
the preset current at an aging degree of 400 cycles. A curve 3 is a
V-Q line graph of charging or discharging the target battery based
on the preset current at an aging degree of 1000 cycles. A curve 4
is a V-Q line graph of charging or discharging the target battery
based on the preset current at an aging degree of 2000 cycles. It
can be seen from FIG. 4 that a capacity that can be released by the
target battery decreases gradually as an aging degree increases, in
other words, as a quantity of cycle times increases, and V-Q curves
have an obvious deviation at the end of discharging.
[0126] It should be noted that, because a voltage in a
small-current condition very approximates to an OCV, the
voltage-capacity curve in this embodiment of this application very
approximates to an existing OCV-capacity curve. This is uniformly
described herein, and details are not described below again.
[0127] Step 2: Convert the voltage-capacity curve into a
voltage-state of charge (V-SOC) curve.
[0128] A charge/discharge capacity of the target battery is
converted into a ratio of a remaining capacity of the target
battery to a full charge capacity of the target battery based on
the voltage-capacity curve obtained in step 1 and according to a
definition of the SOC, to obtain the V-SOC curve.
[0129] For example, FIG. 5 is a V-SOC line graph, corresponding to
FIG. 4, of charging or discharging the target battery based on the
preset current in the new battery state and at the different aging
degrees. It can be seen from FIG. 5 that, when charging or
discharging is performed based on the preset current, V-SOC curves
at different aging degrees present a normalization characteristic.
In this embodiment of this application, the battery SOH is
estimated based on this normalization characteristic.
[0130] Step 3: Obtain a dV/dSOC characteristic curve of the target
battery based on the V-SOC curve.
[0131] For example, dV/dSOC characteristic curves of charging or
discharging the target battery based on the preset current in the
new battery state and at the different aging degrees may be shown
in FIG. 6.
[0132] Step 4: Extract points on the dV/dSOC characteristic curve
for fitting, to obtain the dV/dSOC characteristic function of the
target battery in the new state.
[0133] For example, points in an interval with a highest curve
normalization degree in FIG. 6 may be selected for fitting. For
example, points in a SOC interval from 0 to 0.7 are selected for
fitting.
[0134] When charging or discharging is performed based on the
preset current, the V-SOC curves at the different aging degrees
present the normalization characteristic. Therefore, when charging
or discharging is performed based on the preset current, the
dV/dSOC characteristic function that is of the target battery in
the new state and that is obtained by charging or discharging the
target battery based on the preset current in the new battery state
may also be considered as a dV/dSOC characteristic function of the
target battery at the different aging degrees.
[0135] For example, the dV/dSOC characteristic function may be
shown as formula (4):
g 0 ( SOC n ) = a 0 + j = 1 6 ( a j * sin ( j * .omega. * SOC n ) +
b j * cos ( j * .omega. * SOC n ) ) formula ( 4 ) ##EQU00026##
[0136] The characteristic function is a six-order Fourier function.
SOC.sub.n is an independent variable of the dV/dSOC characteristic
function. g.sub.0(SOC.sub.n) represents second dV/dSOC data
corresponding to SOC.sub.n. j represents an order, a.sub.0,
a.sub.j, and b.sub.j are coefficients of terms, and the order and
the coefficients are all obtained by using a fitting tool. sin( )
represents a sine function. cos( ) represents a cosine function.
.omega. represents frequency.
[0137] FIG. 7 is a schematic diagram of comparing a fitted curve
corresponding to the dV/dSOC characteristic function shown in
formula (4) with an original dV/dSOC characteristic curve, and the
two curves basically coincide.
[0138] Optionally, in this embodiment of this application, when the
dV/dSOC characteristic function is fitted by using a fitting tool,
the fitting is performed by using an example in which the
characteristic function is the six-order Fourier function.
Certainly, in practice, the characteristic function may further
include but is not limited only to a polynomial function, a Fourier
function, an exponential function, and the like. This is not
specifically limited in this embodiment of this application.
[0139] In S3 of step S302:
[0140] Optionally, the calculating, by the apparatus for estimating
a battery SOH, an m.sup.th overall dV/dSOC data deviation of the
plurality of SOCs based on the first dV/dSOC data of each SOC in
the m.sup.th preset battery capacity and the second dV/dSOC data
corresponding to each SOC specifically includes: calculating, by
the apparatus for estimating a battery SOH, the m.sup.th overall
dV/dSOC data deviation of the plurality of SOCs based on the first
dV/dSOC data of each SOC in the m.sup.th preset battery capacity
and the second dV/dSOC data corresponding to each SOC and with
reference to formula (5). Formula (5) includes:
G m = n = 1 N ( g 0 ( SOC n ) - g 1 ( SOC n ) ) 2 formula ( 5 )
##EQU00027##
[0141] N represents a quantity of SOCs, N is a positive integer not
less than 2, and G.sub.m represents the m.sup.th overall dV/dSOC
data deviation of the plurality of SOCs.
[0142] For example, g.sub.1(SOC) may be shown as formula (2),
g.sub.0(SOC) may be shown as formula (4), and the following formula
(6) can be obtained by substituting formula (2) and formula (4)
into formula (5):
G m = n = 1 N ( g 0 ( SOC n ) - g 1 ( SOC n ) ) 2 = n = 1 N ( ( a 0
+ j = 1 6 ( a j * sin ( j * .omega. * SOC n ) + b j * cos ( j *
.omega. * SOC n ) ) ) - Q m ( dV dq ) SOC n ) 2 .quadrature.
formula ( 6 ) ##EQU00028##
[0143] It can be learned that G.sub.m is related to Q.sub.m. Table
1 provides a group of mapping relationships between G.sub.m and
Q.sub.m, as shown below:
TABLE-US-00001 TABLE 1 Q Q.sub.EOL Q.sub.1 . . . . . . Q.sub.m . .
. Q.sub.BOL G G.sub.0 G.sub.1 . . . . . . G.sub.m . . . G.sub.M
[0144] Q.sub.EOL represents a full charge/full discharge capacity
of the target battery at the end of life (EOL), and Q.sub.BOL
represents a full charge/full discharge capacity of the target
battery in the new battery state.
[0145] In step S303:
[0146] The apparatus for estimating a battery SOH may determine the
smallest overall dV/dSOC data deviation from all the overall
dV/dSOC data deviations in a sorting manner, or may determine the
smallest overall dV/dSOC data deviation from all the overall
dV/dSOC data deviations in another manner. This is not specifically
limited in this embodiment of this application.
[0147] In step S304:
[0148] The apparatus for estimating a battery SOH determines the
preset battery capacity corresponding to the smallest overall
dV/dSOC data deviation as the retention capacity of the aged target
battery. It can be learned from the foregoing descriptions that the
dV/dSOC characteristic function that is of the target battery in
the new state and that is obtained by charging or discharging the
target battery based on the preset current in the new battery state
may also be considered as the dV/dSOC characteristic function of
the target battery at the different aging degrees. Therefore,
theoretically, the preset battery capacity corresponding to the
smallest overall dV/dSOC data deviation most approximates to an
estimated capacity value of an actual retention capacity.
[0149] In step S305:
[0150] According to a definition of the SOH, the SOH of the target
battery can be obtained only by dividing the retention capacity of
the aged target battery by the retention capacity of the target
battery in the new battery state.
[0151] In the method for estimating a battery SOH that is provided
in this embodiment of this application, the apparatus for
estimating a battery SOH obtains the partial charge or discharge
capacity of the target battery in the SOC interval of each of the
plurality of SOCs; separately calculates the first dV/dSOC data of
each SOC in the m.sup.th preset battery capacity based on the
m.sup.th preset battery capacity and the partial charge or
discharge capacity in the SOC interval of each SOC; separately
calculates, based on the prestored dV/dSOC characteristic function,
the second dV/dSOC data corresponding to each SOC, where the
dV/dSOC characteristic function is obtained by charging or
discharging the target battery based on the preset current in the
new battery state, the preset current is not greater than 1/20
Q.sub.BOL, and Q.sub.BOL indicates the retention capacity of the
target battery in the new battery state; calculates the m.sup.th
overall dV/dSOC data deviation of the plurality of SOCs based on
the first dV/dSOC data of each SOC in the m.sup.th preset battery
capacity and the second dV/dSOC data corresponding to each SOC;
determines the smallest overall dV/dSOC data deviation from all the
overall dV/dSOC data deviations; determines the preset battery
capacity corresponding to the smallest overall dV/dSOC data
deviation as the retention capacity of the aged target battery; and
determines the SOH of the target battery based on the retention
capacity of the aged target battery. In other words, in this
solution, the retention capacity of the aged target battery is
estimated based on the partial charge or discharge capacity in the
SOC interval of each SOC. In this way, this solution is unlike the
prior art in which the parameter can be obtained only by performing
one full charge or full discharge test, and therefore an
implementation condition of this solution is simpler and more
flexible. In addition, this solution does not need to rely on
historical data, and therefore is more robust.
[0152] The actions of the apparatus for estimating a battery SOH in
the foregoing steps S301 to S305 may be performed by the processor
2601 in the apparatus 26 for estimating a battery SOH that is shown
in FIG. 2, by invoking the application program code stored in the
memory 2603. This is not limited in this embodiment of this
application.
[0153] The foregoing mainly describes the solutions provided in the
embodiments of this application from a perspective that the
apparatus for estimating a battery SOH performs the method for
estimating a battery SOH. It may be understood that to implement
the foregoing functions, the apparatus for estimating a battery SOH
includes corresponding hardware structures and/or software modules
for performing the functions. A person skilled in the art should be
very easily aware that, with reference to the examples described in
the embodiments disclosed in this specification, units and
algorithm steps can be implemented in this application by hardware
or a combination of hardware and computer software. Whether a
function is implemented by hardware or by computer software by
driving hardware depends on particular applications and design
constraints of the technical solutions. A person skilled in the art
may use different methods to implement the described functions for
each particular application, but it should not be considered that
the implementation goes beyond the scope of this application.
[0154] In the embodiments of this application, functional modules
of the apparatus for estimating a battery SOH may be obtained
through division based on the foregoing method examples. For
example, each functional module may be obtained through division
for each corresponding function, or two or more functions may be
integrated into one processing module. The integrated module may be
implemented in a form of hardware, or may be implemented in a form
of a software function module. It should be noted that, in the
embodiments of this application, module division is merely an
example and is merely logical function division. During actual
implementation, there may be another division manner.
[0155] For example, when each functional module is obtained through
division for each corresponding function, FIG. 8 is a possible
schematic structural diagram of an apparatus 80 for estimating a
battery SOH in the foregoing embodiment. The apparatus 80 for
estimating a battery SOH includes an obtaining module 801, a
calculation module 802, and a determining module 803. The obtaining
module 801 is configured to support the apparatus 80 for estimating
a battery SOH in performing step S301 in FIG. 3. The calculation
module 802 is configured to support the apparatus 80 for estimating
a battery SOH in performing steps S302 and S305 in FIG. 3. The
determining module 803 is configured to support the apparatus 80
for estimating a battery SOH in performing steps S303 and S304 in
FIG. 3.
[0156] All related content of the steps in the foregoing method
embodiment can be cited in function descriptions of corresponding
functional modules, and details are not described herein.
[0157] When each functional module is obtained through division in
an integration manner, FIG. 9 is a possible schematic structural
diagram of an apparatus 90 for estimating a battery SOH in the
foregoing embodiment. As shown in FIG. 9, the apparatus 90 for
estimating a battery SOH includes a processing module 901. The
processing module 901 is configured to support the apparatus 90 for
estimating a battery SOH in performing steps S301 to S305 in FIG.
3.
[0158] All related content of the steps in the foregoing method
embodiment can be cited in function descriptions of corresponding
functional modules, and details are not described herein.
[0159] In the embodiments of this application, the apparatus for
estimating a battery SOH is presented in a form that each
functional module is obtained through division for each
corresponding function, or the apparatus for estimating a battery
SOH is presented in a form that each functional module is obtained
through division in an integration manner. The "module" herein may
be an application-specific integrated circuit (ASIC), a circuit, a
processor that executes one or more software or firmware programs
and a memory, an integrated logic circuit, and/or another component
that can provide the foregoing functions. In a simple embodiment, a
person skilled in the art may consider that the apparatus 80 for
estimating a battery SOH or the apparatus 90 for estimating a
battery SOH may use the form shown in FIG. 2. For example, the
obtaining module 801, the calculation module 802, and the
determining module 803 in FIG. 8 may be implemented by the
processor 2601 and the memory 2603 in FIG. 2. Specifically, the
obtaining module 801, the calculation module 802, and the
determining module 803 may be implemented by the processor 2601 by
invoking the application program code stored in the memory 2603.
This is not limited in the embodiments of this application.
Alternatively, for example, the processing module 901 in FIG. 9 may
be implemented by the processor 2601 and the memory 2603 in FIG. 2.
Specifically, the processing module 901 may be implemented by the
processor 2601 by invoking the application program code stored in
the memory 2603. This is not limited in the embodiments of this
application.
[0160] Because the apparatus for estimating a battery SOH that is
provided in the embodiments of this application may be configured
to perform the foregoing method for estimating a battery SOH, for a
technical effect that can be obtained by the apparatus for
estimating a battery SOH, refer to the foregoing method embodiment.
Details are not described herein again in the embodiments of this
application.
[0161] All or some of the foregoing embodiments may be implemented
by software, hardware, firmware, or any combination thereof. When a
software program is used to implement the embodiments, all or some
of the embodiments may be implemented in a form of a computer
program product. The computer program product includes one or more
computer instructions. When the computer program instructions are
loaded and executed on a computer, all or some of the procedures or
functions according to the embodiments of this application are
generated. The computer may be a general-purpose computer, a
dedicated computer, a computer network, or another programmable
apparatus. The computer instructions may be stored in a
computer-readable storage medium or may be transmitted from a
computer-readable storage medium to another computer-readable
storage medium. For example, the computer instructions may be
transmitted from a website, computer, server, or data center to
another website, computer, server, or data center in a wired (e.g.,
a coaxial cable, an optical fiber, or a digital subscriber line) or
wireless (for example, infrared, radio, or microwave) manner. The
computer-readable storage medium may be any usable medium
accessible by a computer, or a data storage device, such as a
server or a data center, integrating one or more usable media. The
usable medium may be a magnetic medium (e.g., a floppy disk, a hard
disk, or a magnetic tape), an optical medium (e.g., a DVD), a
semiconductor medium (e.g., a solid state disk), or the like.
[0162] Although this application is described herein with reference
to the embodiments, in a process of implementing this application
that claims protection, a person skilled in the art may understand
and implement another variation of the disclosed embodiments by
viewing the accompanying drawings, the disclosed content, and the
appended claims. In the claims, "comprising" does not exclude
another component or step, and "a" or "one" does not exclude a case
of "a plurality of". A single processor or another unit may
implement several functions enumerated in the claims. Some measures
are recorded in appended claims that are different from each other,
but this does not mean that these measures cannot be combined to
produce a better effect.
[0163] Although this application is described with reference to
specific features and the embodiments thereof, apparently, various
modifications and combinations may be made to this application
without departing from scope of this application. Correspondingly,
the specification and accompanying drawings are merely example
descriptions of this application defined by the appended claims,
and are considered to cover any of or all modifications,
variations, combinations, or equivalents within the scope of this
application. Apparently, a person skilled in the art can make
various modifications and variations to this application without
departing from the spirit and scope of this application. In this
way, this application is intended to cover these modifications and
variations of this application provided that they fall within the
scope of the claims of this application and equivalent technologies
thereof
* * * * *