U.S. patent application number 11/356117 was filed with the patent office on 2007-08-23 for method and apparatus for monitoring the condition of a battery by measuring its internal resistance.
This patent application is currently assigned to BPPOWER INC.. Invention is credited to Yung-Sheng Huang.
Application Number | 20070194791 11/356117 |
Document ID | / |
Family ID | 38009226 |
Filed Date | 2007-08-23 |
United States Patent
Application |
20070194791 |
Kind Code |
A1 |
Huang; Yung-Sheng |
August 23, 2007 |
Method and apparatus for monitoring the condition of a battery by
measuring its internal resistance
Abstract
A method comprises coupling a first power transistor as a first
external load in series with the battery, coupling a second power
transistor as a second external load in series with the battery,
conducting each power transistor to supply a transient large
current to the battery for sampling a group of sampled reference
voltages and sampled load voltages in a very transient sampling
time for a plurality of times and thus obtaining an internal
resistance of the battery. The internal resistance of the battery
can then be compared with a predetermined warning value thereof so
as to determine whether the former is equal to or larger than the
warning value or not, and issuing a warning through an I/O if the
determination is affirmative. The invention enables a driver to
correctly know the actual condition of the battery in substantially
real time while consuming a minimum amount of power.
Inventors: |
Huang; Yung-Sheng; (Toronto,
CA) |
Correspondence
Address: |
TROXELL LAW OFFICE PLLC
SUITE 1404
5205 LEESBURG PIKE
FALLS CHURCH
VA
22041
US
|
Assignee: |
BPPOWER INC.
|
Family ID: |
38009226 |
Appl. No.: |
11/356117 |
Filed: |
February 17, 2006 |
Current U.S.
Class: |
324/430 |
Current CPC
Class: |
G01R 31/3648 20130101;
G01R 31/389 20190101; G01R 31/3647 20190101 |
Class at
Publication: |
324/430 |
International
Class: |
G01N 27/416 20060101
G01N027/416 |
Claims
1. A method of monitoring the electric power of a battery by
measuring an internal resistance of the battery, comprising the
steps of: (1) coupling a first power transistor at two terminals of
the battery as a first external load with a transient large current
at a very transient sampling time to obtain a reference voltage;
(2) coupling second power transistor at two terminals of the
battery as second external load with a transient large current at a
very transient sampling time to obtain a load voltage; (3)
calculating the internal resistance of the battery by subtracting
the load voltage from the reference voltage and dividing by the
transient large current; and (4) comparing the internal resistance
of the battery with a predetermined warning value thereof such that
a warning can be displayed if the power is lower than a
predetermined level.
2. The method of claim 1, wherein the predetermined warning value
of the internal resistance of the battery to be measured is 0.001
.OMEGA. to 1.5 .OMEGA..
3. The method of claim 1, wherein the resistance of the external
load is in a range from 25u.OMEGA. to 5000 m.OMEGA..
4. The method of claim 1, wherein the resistance of the external
load is optionally coupled to an amplifier.
5. The method of claim 1, wherein the external load is provided as
an internal resistor of either power transistor.
6. The method of claim 1, wherein the transient large current is in
a range from 1 A to 500 A.
7. The method of claim 1, wherein the transient sampling time is
less than 0.01 second.
8. The method of claim 1, wherein a value of the internal
resistance of the battery is measured through Kelvin
connections.
9. A method of measuring the internal resistance of a battery,
comprising the steps of: (1) choosing an external load, the
resistance R of which is selected in accordance with the type of
the battery to be evaluated, (2) selecting a value for the nominal
internal resistance of the battery in accordance with its type; (3)
choosing a first power transistor or its related circuit as a first
external load to obtain a reference voltage Vr; (4) providing the
first power transistor controlled for connecting the first external
load across two terminals of the battery and repetitively
controlling the first power transistor to conduct so that a large
transient current is drawn from the battery by the first external
load at a very transient sampling time and sampling a first
reference voltage V.sub.r1 between two terminals of the battery and
sampling a second reference voltage V.sub.r2 between two terminals
of the external load, respectively for a plurality of times, and
calculating and storing average values of the voltages V.sub.r1 and
V.sub.r2; (5) choosing a second power transistor or its related
circuit as a second external load to obtain a load voltage V.sub.L;
(6) providing the second power transistor controlled for connecting
the second external load across two terminals of the battery and
repetitively controlling the second power transistor to conduct so
that a large transient current is drawn from the battery by the
second external load at a very transient sampling time and sampling
a first load voltage V.sub.L1 between two terminals of the battery
and sampling a second load voltage V.sub.L2 between two terminals
of the external load, respectively for a plurality of times, and
calculating and storing average values of the voltages V.sub.L1 and
V.sub.L2; (7) removing the second external loads for stopping
supplying the transient large current; (8) removing the first
external loads for stopping supplying the transient large current;
(9) determining the large transient current I drawn by the load by
subtracting V.sub.r2 from V.sub.L2 and dividing by the resistance
R; (10) calculating the internal resistance r of the battery by
subtracting V.sub.L1 from V.sub.r1 and dividing by the transient
large current I; (11) comparing the obtained internal resistance of
the battery to be measured with a predetermined warning value of
the internal resistance of the battery to be measured so as to
determine whether the former is equal to or larger than the
predetermined warning value or not; and (12) issuing a warning
through an input and output (I/O) if the determination in step (9)
is affirmative.
10. The method of claim 9, wherein the predetermined warning value
of the internal resistance of the battery to be measured is 0.001
.OMEGA. to 1.5 .OMEGA..
11. The method of claim 9, wherein the resistance of the external
load is in a range from 25 u.OMEGA. to 5000 m.OMEGA..
12. The method of claim 9, wherein the resistance of the external
load is optionally coupled to an amplifier.
13. The method of claim 9, wherein the external load is provided as
an internal resistor of either power transistor.
14. The method of claim 9, wherein the transient large current is
in a range from 1 A to 500 A.
15. The method of claim 9, wherein the transient sampling time is
less than 0.01 second.
16. The method of claim 9, wherein the I/O is one of a display, a
keyboard input, a wireless operation, net work, USB (Universal
Serial Bus) connector, databus, CAN (Controller Area Network) bus,
GPS (Global Positioning System), SMS (Simple Message Service), MMS
(Multimedia Message Service), WAP (Wireless Application Protocol)
or an access to the Internet.
17. The method of claim 9, wherein a value of the internal
resistance of the battery is measured through Kelvin
connections.
18. A method of evaluating the condition of a battery, comprising
the steps of: (1) beginning by setting an interrupt vector address
as an initial address of a program; (2) initializing a register and
I/O pins for setting an initial value of the register, activating
the interrupt vector and a timer, and defining a state and an
initial value of each I/O pin; (3) choosing an external load, a
resistance R of which is based on a type of the battery to be
evaluated; (4) selecting a value for a nominal internal resistance
of the battery in accordance with its type; (5) choosing a first
power transistors as first external load and conducting the first
power transistors for providing the transient large current; (6)
transiently sampling between two terminals of the battery with a
transient large current supplied from the conducted first power
transistor for K1 times, where K1.gtoreq.1 and for L1 times, where
L1.gtoreq.1, respectively so as to obtain an average of each group
of a first sampled reference voltage V.sub.r1 between two terminals
of the battery and a second sampled reference voltage V.sub.r2
between two terminals of the external load; (7) choosing a second
power transistor as second external loads and conducting the second
power transistors for providing the transient large current; (8)
transiently sampling at two terminals of the battery with a
transient large current supplied from the conducted second power
transistor for K2 times, where K2 .gtoreq.1 and for L2 times, where
L2.gtoreq.1, respectively so as to obtain an average of each group
of a first sampled load voltage V.sub.L2 between two terminals of
the battery and a second sampled load voltage V.sub.L1 between two
terminals of the external load; (9) removing the second external
load for stopping supplying the transient large current; (10)
removing the first external load for stopping supplying the
transient large current; (11) determining whether the number of
samplings is equal to N or not, where N .gtoreq.1 and if the
determination is negative then loops back to step (6); (12)
determining the large transient current I drawn by the load by
subtracting V.sub.r2 from V.sub.L2 and dividing by R; (13)
calculating the internal resistance (r) of the battery by
subtracting V.sub.L1 from V.sub.r1 and dividing by the transient
large current I of the battery; and (14) comparing the obtained
internal resistance (r) of the battery to be measured with the
selected nominal value thereof to determine the condition of the
battery to be measured.
19. The method of claim 18, wherein the transient sampling time is
less than 0.01 second.
20. The method of claim 18, wherein the I/O is one of a display, a
keyboard input, a wireless operation, net work, USB (Universal
Serial Bus) connector, databus, CAN (Controller Area Network) bus,
GPS (Global Positioning System), SMS (Simple Message Service), MMS
(Multimedia Message Service), WAP (Wireless Application Protocol)
or an access to the Internet.
21. The method of claim 18, wherein a value of the internal
resistance of the battery is measured through Kelvin
connections.
22. An apparatus for monitoring the condition of a battery by
coupling a first power transistor as a first external load to
obtain a first sampled reference voltage and a second sampled
reference voltage and coupling a second power transistor as a
second external load to obtain a first sampled load voltage and a
second sampled load voltage, comprising: a controller for
controlling the apparatus so as to sample a voltage across the
battery in predetermined periods of time responsive to imposition
of a known external load chosen responsive to the type of the
battery, calculate an internal resistance of the battery to be
measured, and compare the internal resistance of the battery to be
measured with a predetermined warning value therefor; an external
load being a load element and having a predetermined resistance,
the external load comprising the first and second external loads
both coupled in series with the battery, respectively; a
voltage-sampling circuit responsible for sampling voltages across
two terminals of the battery; a transient current control circuit
including the first power transistor and the second power
transistor, when the transient current control circuit is connected
across two terminals of the battery so as to be controlled by the
controller for being served as a switch of the apparatus so that a
large transient current of the first and second power transistors
is drawn by the first and second external loads from the battery
and sampling the above voltages of the battery at a very transient
sampling time for a plurality of times; and dividing a difference
between the second sampled load voltage and the second sampled
reference voltage by the resistance of the external load to obtain
a large transient current of the battery; and dividing a difference
between the average first sampled reference voltage and the average
first sampled load voltage by the large transient current of the
battery so as to obtain the internal resistance of the battery to
be measured; and an input/output(I/O) means responsive to the
controller for issuing a warning responsive to comparison of the
calculated value of the internal resistance of the battery with the
predetermined value thereof.
23. The apparatus of claim 22, wherein the apparatus further
comprises an amplifier optionally coupled to the parallel first and
second transistors taken as load.
24. The apparatus of claim 22, wherein the load element is an
internal resistance of the power transistor.
25. The apparatus of claim 22, wherein the transient current
control circuit comprises two or more parallel power
transistors.
26. The apparatus of claim 22, wherein the resistance of each of
the first and second power transistors is in a range from 25
u.OMEGA. to 5000 m.OMEGA..
27. The apparatus of claim 22 wherein the predetermined warning
value of the internal resistance of the battery to be measured is
0.001 .OMEGA. to 1.5 .OMEGA..
28. The apparatus of claim 22, wherein the transient large current
is in a range from 1 A to 500 A.
29. The apparatus of claim 22, wherein the voltage sampling time is
less than 0.01 second.
30. The apparatus of claim 22, wherein the I/O is one of a display,
a keyboard input, a wireless operation, net work, USB (Universal
Serial Bus) connector, databus, CAN (Controller Area Network) bus,
GPS (Global Positioning System), SMS (Simple Message Service), MMS
(Multimedia Message Service), WAP (Wireless Application Protocol)
or an access to the Internet.
31. The apparatus of claim 22, wherein a value of the internal
resistance of the battery is measured through Kelvin connections.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to monitoring apparatus and
more particularly to a method of monitoring the electric power of a
battery by measuring the internal resistance of the battery by
means of conducting a first power transistor as a first external
load to obtain a reference voltage and then conducting second power
transistor as second external load to obtain a load voltage and
comparing the internal resistance of the battery with a
predetermined warning value thereof such that a warning can be
displayed if the power is lower than a predetermined level prior to
starting the engine. The present invention further particularly
relates to such a monitoring apparatus.
[0003] 2. Description of Related Art
[0004] It is known that a driver has to start the engine of a motor
vehicle before driving it. Also, for successfully starting the
engine, there must be sufficient electric power stored in the
battery. Typically, a battery has an approximate lifetime. However,
factors such as ambient temperature, charging conditions and time,
and load discharge all can adversely affect the lifetime of the
battery. Thus, there is difference between the practical lifetime
and the approximate lifetime of any particular battery and the
difference is sometimes very large. Hence, in practice, there is no
way for a driver (or even an experienced one) to know the electric
power level of the battery prior to starting the engine. Typically,
only a motor vehicle repair shop technician is able to know the
electric power level by means of a test device. However, the test
device is somewhat bulky, thus prohibiting it from being carried by
the motor vehicle. It is common that a driver finds the battery to
be low only when it fails to start the engine. Alternatively, the
battery may be already damaged but the driver is not aware before
next start even it is successful in a particular start. This is not
desirable and may even be dangerous since the driver may park
his/her car in a remote area, mountain, or desert.
[0005] Advantageously, a battery power measuring device would be
installed in a car as requisite equipment. But power measurement of
the battery may also consume the electric power of the battery.
Hence, a frequent power measurements is not desirable. Thus, it is
specially desirable to accurately measure the electric power of
battery in a relatively short period of time by consuming a minimum
amount of electric power thereof. The present application is
relevant to commonly assigned U.S. Pat. Nos. 6,704,629 and
6,791,464 both entitled "Device for Monitoring Motor Vehicle's
Electric Power and Method Thereof". The present application is
closely relevant to a pending application with a Pub. No. US
2006/0001429 A1. The patent relates to a method and apparatus for
monitoring the condition of a battery by measuring its internal
resistance at two terminals of the battery by using a floating
voltage V.sub.0 as its reference voltage to compare with a sampling
voltage. However, a value of the floating voltage V.sub.0 itself is
not stable as it will be affected by intermittently charging on the
battery or up and down variation of load at two terminals of the
battery or ageing of the battery.
[0006] Tsuji U.S. Pat. No. 6,072,300 relates to characterization of
the individual batteries of a large set of batteries. Internal
resistance is estimated from cell voltage. See Col. 5, lines
32-38.
[0007] Fakruddin U.S. Pat. No. 5,027,294 also characterizes battery
condition based on measurements of voltage.
[0008] Huang U.S. Pat. No. 6,704,629, to the present inventor,
measures battery condition in part by drawing a substantial current
from the battery by connecting a significant load to it for a short
period of time, as is part of the method of the present invention,
but measures voltage only.
[0009] Arai U.S. Pat. No. 6,201,373 shows a circuit for measuring
the state of charge (SOC) of a battery, not a battery condition
evaluation device per se. Voltage and current are both sampled.
[0010] Hirzel U.S. Pat. No. 5,381,096 also relates to SOC
measurement.
[0011] Satake U.S. Pat. No. 6,531,875 teaches estimating the open
circuit voltage of a battery based on extrapolation from a series
of measurements.
[0012] Disser et al. Pub. No. US 2003/0067221 A1 shows voltage
regulator circuitry for automotive use.
[0013] Yokoo U.S. Pat. No. 5,828,218 shows a method for estimating
residual capacity of a battery based on discharge current and
voltage during discharge.
[0014] Munson patent 5,900,734 shows a battery monitoring system
wherein the battery voltage is compared to a fixed reference value
and an alarm is given when the battery voltage is less than the
reference value.
[0015] Bramwell U.S. Pat. No. 6,097,193 discusses various methods
of measuring the internal resistance and/or impedance of a battery,
including application of a small AC signal to the battery and using
a Wheatstone bridge or equivalent to measure the internal
resistance. See col. 1, lines 40-48. Bramwell's claimed method
includes the steps of measuring impedance of a battery by sourcing
to or sinking from the battery a current of known magnitude while
intervals while the vehicle sits. Col. 9, lines 18-50. An alarm
message can be given when QV falls below a predetermined
point--Col. 11, lines 28-39. Gollomp also measuring the terminal
voltage, and determining the impedance therefrom.
[0016] Turner et al. U.S. Pat. No. 6,249,106 shows a circuit for
preventing discharge of a battery beyond a predetermined point.
Yorksie et al. U.S. Pat. No. 3,852,732 is directed toward the same
objective. Finger et al. U.S. Pat. No. 4,193,026 is directed to
measuring the SOC of a battery by integrating a signal indicative
of reduction of the terminal voltage below a threshold value.
[0017] Reher et al. U.S. Pat. No. 5,130,699 shows a device for
monitoring a battery by measuring the terminal voltage at regular
intervals, comparing the measured values to a predetermined value,
and setting a flag in a shift register depending on the result.
When a predetermined number of flags indicate an under voltage
condition an alarm is given.
[0018] Sato et al. U.S. Pat. No. 5,193,067 discloses determining
the internal impedance of a battery by measuring the voltage during
discharge of a predetermined current, or by measuring the current
during discharge at a predetermined voltage.
[0019] Slepian U.S. Pat. No. 5,764,469 shows disconnecting
electronic equipment of a vehicle when the battery voltage falls
below a predetermined level.
[0020] Huang U.S. Pat. No. 6,791,464, to the present inventor,
shows evaluation of the condition of a motor vehicle's battery by
monitoring the voltage across the battery during starting, while
the starter provides a substantial load. The minimum voltage
reached during starting can be compared to predetermined value to
evaluate the condition of the battery.
[0021] Gollomp et al. U.S. Pat. No. 6,424,157 refers to the
difficulty of measuring battery SOC from open-circuit voltage (OCV)
because this requires that everything be disconnected. Gollomp
instead teaches monitoring of the quiescent voltage (QV), e.g.,
measured at 30 minutes intervals while the vehicle sits. Col. 9,
lines 18-50. An alarm message can be given when QV falls below a
predetermined point--Col. 11, lines 28-39. Gollomp also teaches
monitoring of voltage and current during engine starting. See FIG.
6. This data is stored in memory, see Col. 12, lines 48-50, and
used to determine dynamic internal resistance (IR) and polarization
resistance (PR). Gollomp also teaches monitoring SOC and QV over
time to determine when the battery won't be able to start the car;
see FIG. 3, Col. 14, line 22--Col. 16, line 36. Gollomp also
teaches storing the first IR value of the battery, or some
subsequent one, for "future use"--e.g., determination of IR change
over time. PR is similarly monitored over time; see Col. 17, line
12-Col. 18, line 35. The result is to give warning of incipient
battery failure or some problem with connections or the like. These
data can be monitored during successive starts--see claim 1.
[0022] Kchao patent 5,751,217 shows a method and circuit for
assessing battery impedance, which is stated to be applicable only
to fully charged batteries, see Col. 3, lines 49-55, and Col. 4,
line 12, and which is intended to be incorporated in a battery
charger. Applicant's device is not limited to fully charged
batteries and can be economically provided as a stand-alone
unit.
SUMMARY OF THE INVENTION
[0023] It is an object of the present invention to provide an
apparatus of long-term monitoring or short time test at two
terminals of the battery in a relatively transient sampling time
with a transient large current by consuming a minimum amount of
electric power thereof such that a warning can be displayed for the
driver via an I/O operation if the power is lower than a
predetermined level during running of the engine or prior to
starting the engine.
[0024] It is a further object of the present invention to provide a
method of monitoring electric power of a battery, comprising the
steps of (1) setting a resistance of an external load based on
battery type and an internal resistance of the battery to be
measured; (2) setting an internal resistance of the battery to be
measured; (3) transiently sampling at two terminals of the battery
to be measured with a transient large current supplied from a
conducted first power transistor for a plurality of first and
second times so as to obtain an average of each group of first and
second sampled reference voltages; (4) transiently sampling at two
terminals of the battery to be measured with a transient large
current supplied from a conducted second power transistor for a
plurality of first and second times so as to obtain an average of
each group of first and second sampled load voltages; (5) removing
the first and second power transistors; (6) dividing a difference
between the second sampled load voltage and the second sampled
reference voltage by the resistance of the external load to obtain
a transient large current of the battery; (7) dividing a difference
between the average first sampled reference voltage and the average
first sampled load voltage by the transient large current of the
battery to obtain the internal resistance of the battery; (8)
comparing the obtained internal resistance of the battery to be
measured with a predetermined warning value of the internal
resistance of the battery so as to determine whether the former is
equal to or larger than the predetermined warning value or not; and
(9) issuing a warning through an I/O if the determination in step
(8) is affirmative. By utilizing this method, it is possible of
enabling a driver to know the actual electric power capacity of the
battery in substantially real time.
[0025] It is another object of the present invention to provide a
method of monitoring electric power of a battery, comprising: (1)
coupling a first power transistor to two terminals of the battery
as a first external load with a transient large current at a very
transient sampling time to obtain a reference voltage;
[0026] (2) coupling second power transistor to two terminals of the
battery as second external load with a transient large current at a
very transient sampling time to obtain a load voltage;
[0027] (3) calculating the internal resistance of the battery by
subtracting the load voltage from the reference voltage and
dividing by the transient large current; and
[0028] (4) comparing the internal resistance of the battery with a
predetermined warning value thereof such that a warning can be
displayed if the power is lower than a predetermined level.
[0029] It is a further object of the present invention to provide
an apparatus for monitoring electric power of a battery, comprising
a MCU (microprocessor control unit) responsible for controlling the
apparatus so as to sample a voltage of the battery to be measured
in predetermined periods of time, calculate an internal resistance
of the battery to be measured, and compare the internal resistance
of the battery to be measured with a predetermined warning value of
the internal resistance of the battery to be measured; first and
second external loads both coupled in series with the battery to be
measured so as to calculate the internal resistance of the battery
to be measured; a voltage-sampling circuit responsible for sampling
voltages of two terminals of the battery to be measured, the first
power transistor, and the second power transistor with a transient
large amount of current; a transient current control circuit
including a first power transistor in series with the first
external load, and a second power transistor in series with the
second external load so as to be controlled by the MCU for being
served as a switch of the apparatus and being responsible for
controlling a magnitude of transient current of the first and
second power transistors and sampling voltage of the battery to be
measured; and an I/O responsible for issuing a warning if the
comparison done by the MCU shows the internal resistance of the
battery to be measured is equal to or larger than the predetermined
warning value of the internal resistance of the battery to be
measured.
[0030] The above and other objects, features and advantages of the
present invention will become apparent from the following detailed
description taken with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is a flow chart illustrating a process of monitoring
the electric power, i.e. the condition, of battery according to the
invention;
[0032] FIG. 2 is a detailed flow chart illustrating the FIG. 1
process;
[0033] FIG. 3 is an electrical block diagram of a first preferred
embodiment of apparatus for monitoring the battery's electric power
according to the invention;
[0034] FIG. 4 is an electrical block diagram of a second preferred
embodiment of apparatus for monitoring the battery's electric power
according to the invention;
[0035] FIG. 5 is an electrical block diagram of a third preferred
embodiment of apparatus for monitoring the battery's electric power
according to the invention;
[0036] FIG. 6 is an electrical block diagram of a fourth preferred
embodiment of apparatus for monitoring the battery's electric power
according to the invention;
[0037] FIG. 7 plots sampled voltage versus sampling time for
voltage curves according to the invention;
[0038] FIG. 8 plots internal resistance of the battery versus
discharge percentage for a discharge curve according to the
invention; and
[0039] FIG. 9 is an equivalent circuit of the battery and a series
external load according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0040] Referring to FIGS. 1 and 8, a process of monitoring the
electric power of a battery (e.g., one installed in an automobile)
according to the invention is illustrated.
[0041] In step 1, the resistance R of an external load is set, that
is selected from values between 25u.OMEGA. to 5000m.OMEGA.
optionally by means of using an amplifier based on battery type and
an internal resistance of the battery to be measured.
[0042] In step 2, the predetermined value to which the internal
resistance r of the battery will be compared is selected from the
range of 0.001 .OMEGA. to 1.5.OMEGA. based on the battery type. An
appropriate setting depends on applications so as to provide a
predetermined value, a warning range, or one of a plurality of
predetermined warning values for multiple stages of warning before
the end of discharging (see FIG. 8).
[0043] In step 3, a first power transistor Q1 or its related
circuit is controlled to conduct as a first external load. Obtain a
plurality of reference voltages thereof and store same.
[0044] In step 4, the reference voltages at two terminals of the
battery and the external load are sampled while a transient large
current is drawn by the first external load by controlling the
first power transistor Q1 to conduct transiently for a plurality of
times, that is intermittently, so as to obtain a plurality of an
average of each group of first and second sampled reference
voltages. A reference voltage curve is formed by connecting a
plurality of the first and second sampled reference voltages
together.
[0045] In step 5, a second power transistor Q2 or its related
circuit is controlled to conduct as a second external load. Obtain
a load voltage thereof and store same.
[0046] In step 6, the load voltages at two terminals of the battery
and the external load are sampled while a transient large current
is drawn by the second external load by controlling the second
power transistor Q2 to conduct transiently for a plurality of
times, that is intermittently, so as to obtain an average of each
group of first and second sampled load voltages. A load voltage
curve is formed by connecting a plurality of the first and second
sampled load voltages together.
[0047] In step 7, remove the second external load (i.e., the
transistor Q2).
[0048] In step 8, remove the first external load (i.e., the
transistor Q1).
[0049] In step 9, a difference between average load voltage sampled
at second times and average reference voltage sampled at second
times is divided by the resistance of the external load (R) to
obtain a current of the battery. And in turn, an internal
resistance (r) of the battery to be measured is obtained by
dividing a difference between average reference voltage sampled at
first times and average load voltage sampled at first times by the
current (I) of the battery. Next, the obtained internal resistance
of the battery is compared with the predetermined value of internal
resistance (r) of the battery so as to determine whether the former
is in a predetermined warning range or not.
[0050] In step 10, an input and output (I/O) operation is performed
in response to the comparison result in step 9. The I/O may be one
of the followings, for example, such as a display, a keyboard
input, a wireless operation, USB (Universal Serial Bus) connector,
databus, CAN (Controller Area Network) bus, GPS (Global Positioning
System), SMS (Simple Message Service), MMS (Multimedia Message
Service), WAP (Wireless Application Protocol), net work or an
access to the Internet.
[0051] Referring to FIGS. 2, 7 and 8, detailed method steps of the
above process are illustrated.
[0052] In step 11, the process begins by setting an interrupt
vector address as an initial address of a program.
[0053] In step 12, a register and I/O pins are initialized for
setting an initial value of the register, the interrupt vector and
timer are activated, and state and initial value of each I/O pin is
defined.
[0054] In step 13, the resistance (R) of the external load is set
as 25 u.OMEGA. to 5000 m.OMEGA. based on requirement of battery
type and an internal resistance of the battery to be measured. The
resistance R of the external load can be amplified.
[0055] In step 14, the predetermined value to which the internal
resistance r of the battery will be compared is set as 0.001.OMEGA.
to 1.5.OMEGA. based on the battery type. An appropriate setting
value depends on applications so as to provide a predetermined
warning value before the end of discharging (see FIG. 8).
[0056] In step 14a, a first power transistor Q1 or its related
circuit served as a first external load is controlled to conduct so
that a large amount of transient current is drawn. A reference
voltage Vr thereof (see FIG. 7) is obtained.
[0057] In step 15, the reference voltage Vr is sampled for a
plurality of times. The transient sampling time is set within 0.01
second. As shown in FIG. 7, providing a very large transient
current by conducting the first power transistor Q1 or its related
circuit between the two terminals of the battery, the reference
voltage V.sub.r1 (as shown in FIG. 7) between two terminals of the
battery to be measured is sampled for K1 times, where K1.gtoreq.1,
the reference voltage V.sub.r2 between two terminals of the
external load is sampled for L1 times, where L1.gtoreq.1, and
average value of voltages V.sub.r1 and V.sub.r2 are therefore
calculated and stored. The large transient current is preferably in
the range of 1 A to 500 A.
[0058] In step 15a, a second power transistor Q2 or its related
circuit served as a second external load is operated to conduct so
that a large amount of transient current is drawn. A load voltage
thereof V.sub.L (see FIG. 7) is obtained.
[0059] In step 15b, the load voltage V.sub.L is sampled in a
plurality of times. The transient sampling time is set within 0.01
second. As shown in FIG. 7, providing a transient large current by
conducting the second power transistor Q2 or its related circuit
between the two terminals of the battery, the load voltage V.sub.L1
between two terminals of the battery to be measured is sampled for
K2 times, where K2.gtoreq.1, the load voltage V.sub.L2 between two
terminals of the load is sampled for L2 times, where L2.gtoreq.1,
and the average value of voltages V.sub.L1 and V.sub.L2 are
calculated and stored. The large transient current is preferably in
the range of 1 A to 500 A.
[0060] More specifically, "large transient current" as used herein
is typically a current equal to between IC and 5C, where C, as is
usual in the industry, is the number of ampere-hours (a-h) that can
be provided by a given battery in 20 hours. For example, a battery
rated at 34 a-h can deliver 34 a-h if discharged over a period of
20 hours, so 1 C for this battery is 34 amperes
[0061] In step 15c, the second external load having second load
resistance (i.e., second power transistor Q2 or its related
circuit) is removed. The second power transistor Q2 or its related
circuit is cut off with no transient large current output.
[0062] In step 15d, the first external load having first load
resistance (i.e., first power transistor Q1 or its related circuit)
is removed. The first power transistor Q1 or its related circuit is
cut off with no transient large current output
[0063] In step 15e, it is determined whether the number of samples
is equal to N, where N.gtoreq.1. If yes, the process goes to step
16. Otherwise, the process loops back to step 15.
[0064] In step 16, the average of the internal resistance (r) of
the battery to be measured is calculated by referring to FIG. 9 as
below. Current I of the battery to be measured is obtained by the
following equation. I = V L .times. .times. 2 - V r .times. .times.
2 R = .DELTA. .times. .times. V L R EQ .times. .times. 1
##EQU1##
[0065] Further, the internal resistance (r) of the battery to be
measured is calculated by the following equation. r = V r .times.
.times. 1 - V L .times. .times. 1 I = .DELTA. .times. .times. V r I
EQ .times. .times. 2 ##EQU2##
[0066] More specifically, in order to fully understand the above
two equations, let us assume the value of the external load R=1
m.OMEGA., as viewed from FIG. 7, the curve VB represents the
voltage across two terminals of the battery to be measured, and the
curve VR represents the voltage across two terminals of the
external load R. It is assumed that in the FIG. 7, the values
are
[0067] V.sub.0=12.70 volt, V.sub.r1=12.30 volt, V.sub.L1=11.55
volt, Vg=0 volt, V.sub.r2=0.25 volt, V.sub.L2=0.4 volt. Thus, from
the EQ1, we obtain the transient large current
I=.DELTA.V.sub.L/R,
[0068] I=(0.4-0.25)/1.times.0.001=0.15/0.001=150 (amperes); and
[0069] From the EQ2, we obtain the value of internal resistance (r)
of the battery as
[0070] r=.DELTA.V.sub.r/I=(12.30-11.55)/150=0.005 (.OMEGA.)=5
(m.OMEGA.).
[0071] In step 17, the internal resistance (r) of the battery
obtained in step 16 is compared with the predetermined value of
internal resistance of the battery selected in step 14 so as to
determine whether the former is in a warning range or not.
[0072] In step 18, an I/O (e.g., a keyboard input, a wireless
operation, net work, USB (Universal Serial Bus) connector, databus,
CAN (ControllerArea Network) bus, GPS (Global Positioning System),
SMS (Simple Message Service), MMS (Multimedia Message Service), WAP
(Wireless Application Protocol) or an access to the Internet is
performed in response to reaching the value in step 17.
[0073] In step 18a, a new internal resistance r.sub.new via I/O is
setting for a next sampling cycle. If yes, the process loops back
to step 14a. Otherwise, the process goes to step 19.
[0074] In step 19, timer begins to count time.
[0075] In step 20, it is determined whether time is equal to time
T2 of a next sampling. If yes, the process loops back to step 14a
for a next sampling. Otherwise, the process loops back to step 19.
That is, the condition of the battery is evaluated from time to
time, so as to reduce the total current drawn.
[0076] The voltage sampling process from step 15 to step 15e takes
one period of time. This is depicted in the graph of FIG. 7 of
sampled voltage versus sampling time for voltage curves according
to the invention. Voltage curve V.sub.r1 represents a reference
voltage taken at two terminals of the battery 7 to be measured and
voltage curve V.sub.r2 represents a reference voltage taken at two
terminals of the first external load (see FIGS. 3 and 4) when a
transient large current is generated by the conducted the first
power transistor Q1 due to voltage change from no load state to
first external load state. Voltage curve V.sub.L1 represents the
first load voltages taken at two terminals of the battery 7 to be
measured and voltage curve V.sub.L2 represents the first load
voltages taken at two terminals of the second external load (see
FIGS. 3 and 4) when a transient large current is generated by the
conducted the second power transistor Q2 due to voltage change from
the first external load state to the second external load state. In
the graph of FIG. 7, reference voltages V.sub.r1 and V.sub.r2 are
obtained in step 15 and load voltages V.sub.L1 and V.sub.L2 are
obtained in step 15b.
[0077] Referring to the voltage curves in FIG. 7 again, the
sampling with respect to respective voltage curves can be best
understood. Curves V.sub.r1 and V.sub.r2 are the reference voltage
curves by conducting the first power transistor Q1 and curves
V.sub.L1 and V.sub.L2 are the load voltage curves of the second
external load (i.e., second power transistor Q2). In detail,
voltage curve V.sub.r1 represents that a reference voltage of the
first power transistor Q1 has been sampled for K1 times. Voltage
curve V.sub.L1 represents that a load voltage of the second power
transistor Q2 has been operated to conduct for K2 times. Likewise,
Voltage curve V.sub.r2 represents that a reference voltage of the
first power transistor Q1 has been operated to conducted for L1
times. Voltage curve V.sub.L2 represents that a load voltage of the
second power transistor Q2 has been operated to conducted for L2
times. .DELTA.Vr is a difference between V.sub.r1 and V.sub.L1.
.DELTA.V.sub.L is a difference between V.sub.L2 and V.sub.r2.
[0078] Referring to FIG. 3, there is shown an electrical block
diagram of a first preferred embodiment of apparatus 60 for
monitoring the battery's electric power according to the invention.
It illustrates a Kelvin connection formed by connections 64A and
64B, 65A and 65B, to battery 7. With such a Kelvin connection, two
couplings are provided to the positive and negative terminals of
battery 7. This allows the one pair of the electrical connections
65A and 65B at two terminals of the battery to draw a large amount
of transient current while the other pair of connections 64A and
64B can be used to sample accurate voltage reading values. As the
resistance value between connections A/D and 65A, 65B is very
little and substantially no current is flowing through the
connections A/D and 65A, 65B, there will be little voltage drop
through the electrical connection between connections A/D and 65A,
65B, thereby providing more accurate voltage measurements.
[0079] The apparatus 60 comprises a MCU (microprocessor control
unit) 62, a voltage-stabilizing circuit 61 (optionally provided
depending on the actual applications), an external loads 63 and 66,
a voltage-sampling circuit 64, a transient current control circuit
65, and an I/O 66. Each component will be described in detailed
below.
[0080] The MCU 62 is responsible for controlling the apparatus 60
so as to send signals to the battery 7 for sampling its voltage in
predetermined periods of time, calculate the internal resistance r
of the battery 7, and compare the warning value of internal
resistance r with a predetermined value thereof for warning if
necessary. The voltage-stabilizing circuit 61 is optionally used
for providing a stable voltage to the apparatus 60 during operating
periods, that is, if the apparatus 60 used a stable DC cell or
battery, then, the voltage-stabilizing circuit 61 can be omitted
accordingly. The external loads 63 and 66 have a predetermined
resistance. In a preferred embodiment of the invention, the
external loads 63 and 66 are a combination of parallel resistors R1
and R2 (or their related circuit). The resistance R1 of the first
external load 63(i.e., the first power transistor Q1 or its related
circuit) is set as 25 u.OMEGA. to 5000m.OMEGA. and is provided
directly in series with the battery and the resistance R2 of the
second external load 66 (i.e., the second power transistor Q2 or
its related circuit) is set as 25u/.OMEGA. to 5000m/.OMEGA. and is
also provided directly in series with the battery so as to
calculate the internal resistance r of the battery. Note that the
external loads 63 and 66 have a substantially very low resistance
so as to be able to sample the voltage of the battery 7 in a very s
transient sampling time with a very larger amount of transient
current. For example, sampling voltage by optionally applying a
large amount of transient current 1 A to 500A is required (i.e., to
sample voltage) within 0.01 second. Also note that the external
loads 63 and 66 are implemented as a resistor such as Manganin or
formed of any of a number of other alloys known to the art.
Alternatively, the external loads 63 and 66 can be implemented as a
switching element having a resistance, for example, the internal
resistance of the first and second power transistors Q1, Q2. It
means that the internal resistance of the first and second power
transistors Q1, Q2 in the transient current control circuit 65 can
be used as the external loads so that the external load 63, 66
(i.e., resistors R1 and R2) in this embodiment can be omitted from
the circuit 65A-65B of FIG. 3. Furthermore, the external loads 63,
66 can also be implemented by a portion of conductor extended
between two terminals of the battery, such as a portion of
conductor between two terminals 63E and 63F (without R1), two
terminals 66E and 66F (without R2) or the conductor between A/D
i.e. terminals 63A-63E, 63C-63F, 66A-66E, 66C-66F. Note that in a
preferred embodiment of the invention the voltage-sampling circuit
64 is responsible for sampling voltage across two terminals 64A,
64B. As shown in FIG. 3, one terminal 64A is electrically
interconnected to a positive terminal of A/D pin of MCU 62 and a
positive terminal of the battery 7 and the other terminal 64B is
electrically interconnected to a negative terminal of A/D pin of
MCU 62 and a negative terminal of the battery 7. As an end, a
correct voltage can be sampled. That is, signal conductors
connected to terminals 64A, 64B allow measurement of the voltage
across the battery separately from the voltage across the load R.
The transient current control circuit 65 is controlled by the MCU
62. In a preferred embodiment of the invention, the transient
current control circuit 65 is implemented as the first power
transistor Q1 and the second power transistor Q2 both connected in
parallel to the battery. The transient current control circuit 65
serves as a switch of the apparatus and is responsible for
controlling the magnitude of transient large current of the load.
That is, a regulated transient large current is drawn from the
battery 7 for sampling voltage thereof during voltage sampling
periods. The I/O 66 is responsible for indicating a warning by
means of a keyboard input, a wireless operation, net work, USB
(Universal Serial Bus) connector, databus, CAN (Controller Area
Network) bus, GPS (Global Positioning System), SMS (Simple Message
Service), MMS (Multimedia Message Service), WAP (Wireless
Application Protocol) or an access to the Internet if the
comparison of the internal resistance of the battery with the set
warning value of internal resistance of the battery by the MCU 62
shows that a warning value has been reached.
[0081] In brief, after connecting the apparatus 60 of monitoring
the battery's electric power according to the invention to the
battery 7, optionally, the voltage-stabilizing circuit 61 provides
required voltage to the apparatus including the MCU 62 during
operating periods. The MCU 62 then performs above operations based
on the method of monitoring electric power by comparing internal
resistance of its battery with that of external load. First, the
voltage-sampling circuit 64 samples voltage of the battery 7 when
the external load is temporarily removed. After adding the first
external load 63 (i.e., power transistors Q1) to the apparatus, the
transistor Q1 of the transient current control circuit 65 is
controlled to conduct to provide a transient large amount of
current. Next, the voltage-sampling circuit 64 samples reference
voltages Vri across two terminals of the battery 7 and V.sub.r2
across two terminals of the external loads 63, respectively.
Further, adding the second external load 66 (i.e., power transistor
Q2) to the apparatus, the second power transistor Q2 of the
transient current control circuit 65 conducts to provide a
transient large amount of current. Next, the voltage-sampling
circuit 64 samples load voltage V.sub.L1 across two terminals of
the battery 7 and V.sub.L2 across two terminals of the external
loads 66. After sampling reference voltages and load voltages for N
times in a predetermined period of time, the MCU 62 removes the
second load Q2 and then the first load Q1. The MCU 62 then
calculates the internal resistance r of the battery 7 by means of
the sampled reference and load voltages and two equations as
described above in step 16 of FIG. 2. Furthermore, the obtained
internal resistance r of the battery 7 is compared with the
predetermined value of internal resistance of the battery. As an
end, a warning is issued through the I/O 66 if necessary.
[0082] Referring to FIG. 4, there is shown an electrical block
diagram of a second preferred embodiment of apparatus 60 of
monitoring the battery's electric power according to the invention.
The second preferred embodiment substantially has same structure as
the first preferred embodiment. The characteristics of the second
preferred embodiment are detailed below. The transient current
control circuit 65 of the apparatus 60 is implemented as two
parallel transistors Q1 and Q2. The transistors Q1 and Q2 are
sequentially conducted so as to obtain a lowest voltage value of
two terminals.
[0083] Referring to FIG. 5, there is shown an electrical block
diagram of a third preferred embodiment of apparatus 60 of
monitoring the battery's electric power according to the invention.
The third preferred embodiment substantially has same structure as
the second preferred embodiment. The characteristics of the third
preferred embodiment are detailed below. The external load 63 has a
very low resistance. An amplifier 67 is optionally interconnected
the external load 63 and the MCU 62. Preferably, the external load
63 has a resistance lower than 5000 u.OMEGA..
[0084] Referring to FIG. 6, there is shown an electrical block
diagram of a fourth preferred embodiment of apparatus 60 of
monitoring the battery's electric power according to the invention.
The fourth preferred embodiment substantially has same structure as
the second preferred embodiment. The characteristics of the fourth
preferred embodiment are detailed below. The external load 63 is
implemented as a shunt unit S labeled as 63S. In the preferred
embodiment, a shunt load of the single battery to be measured is
implemented as a shunt circuit for obtaining the same effect as any
of the above embodiments.
[0085] While the invention herein disclosed has been described by
means of specific embodiments, numerous modifications and
variations could be made thereto by those skilled in the art
without departing from the scope and spirit of the invention set
forth in the claims.
* * * * *