U.S. patent application number 14/787364 was filed with the patent office on 2016-04-21 for method and system for charging a motor vehicle battery according to temperature.
This patent application is currently assigned to RENAULT S.A.S. The applicant listed for this patent is RENAULT S.A.S. Invention is credited to Bruno DELOBEL, Laureline MARCHAL, Julien MARIE, Anais RICAUD, Juan-Pablo SOULIER.
Application Number | 20160107535 14/787364 |
Document ID | / |
Family ID | 48979951 |
Filed Date | 2016-04-21 |
United States Patent
Application |
20160107535 |
Kind Code |
A1 |
DELOBEL; Bruno ; et
al. |
April 21, 2016 |
METHOD AND SYSTEM FOR CHARGING A MOTOR VEHICLE BATTERY ACCORDING TO
TEMPERATURE
Abstract
A method for charging a motor vehicle battery includes
determining the electrolyte resistance frequency of the cell,
determining the battery charge transfer resistance frequency, and
charging the battery with a current at a charging current frequency
greater than the electrolyte resistance frequency of the battery
and less than the battery charge transfer resistance frequency.
Inventors: |
DELOBEL; Bruno; (Issy Les
Moulineaux, FR) ; MARIE; Julien; (Sceaux, FR)
; RICAUD; Anais; (Guyancourt, FR) ; SOULIER;
Juan-Pablo; (Paris, FR) ; MARCHAL; Laureline;
(Guyancourt, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
RENAULT S.A.S |
Boulogne-Billancourt |
|
FR |
|
|
Assignee: |
RENAULT S.A.S
Boulogne-Billancourt
FR
|
Family ID: |
48979951 |
Appl. No.: |
14/787364 |
Filed: |
April 28, 2014 |
PCT Filed: |
April 28, 2014 |
PCT NO: |
PCT/FR2014/051014 |
371 Date: |
December 1, 2015 |
Current U.S.
Class: |
320/162 |
Current CPC
Class: |
H01M 10/44 20130101;
Y02T 90/12 20130101; B60L 11/1861 20130101; H02J 7/00 20130101;
B60L 53/62 20190201; H02J 7/0003 20130101; Y02E 60/10 20130101;
Y02T 10/70 20130101; Y02T 10/7072 20130101; B60L 58/15 20190201;
H01M 10/48 20130101; H01M 2220/20 20130101; H01M 10/443 20130101;
H02J 7/00047 20200101; H02J 7/007 20130101 |
International
Class: |
B60L 11/18 20060101
B60L011/18 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 29, 2013 |
FR |
1353914 |
Claims
1. A method for charging a motor vehicle battery, comprising:
determining the electrolyte resistance frequency of the battery,
determining the charge transfer resistance frequency of the
battery, and charging the battery with a current with a charge
current frequency which is higher than the battery electrolyte
resistance frequency and lower than the battery charge transfer
resistance frequency.
2. The method as claimed in claim 1, wherein from a complex
representation of the impedance as a function of the charge current
frequency, the electrolyte resistance frequency is determined as
the impedance frequency with a zero value of its imaginary part and
the lowest value of the actual part, and the charge transfer
resistance frequency as the impedance frequency with a minimal
value of its imaginary part and the highest value of the actual
part.
3. The method as claimed in claim 1, wherein from a representation
of the impedance as a function of the charge current phase shift,
the electrolyte resistance frequency is determined as the frequency
for which the phase shift is cancelled out, and the charge transfer
resistance frequency as the frequency for which the derivative of
the phase shift as a function of frequency is cancelled out.
4. The method as claimed in claim 1, wherein from a representation
of the imaginary part over the cell impedance as a function of the
charge current frequency, the electrolyte resistance frequency is
determined as the frequency for which the imaginary part is
cancelled out, and the charge transfer resistance frequency as the
frequency for which the derivative of the imaginary part as a
function of frequency is cancelled out.
5. The method as claimed in claim 1, wherein the charge current
frequency lies between 10 Hz and 300 Hz, preferably equal to 100
Hz.
6. The method as claimed in claim 1, wherein new battery
electrolyte resistance and battery charge transfer resistance
frequencies of the battery are determined when the temperature
changes.
7. A system for charging a motor vehicle battery, comprising: means
for determining the electrolyte resistance frequency of the
battery, means for determining the charge transfer resistance
frequency of the battery, and means for controlling the battery
charge current and able to control the battery charging by a
current with a frequency which is higher than the battery
electrolyte resistance frequency and lower than the battery charge
transfer resistance frequency.
8. The system as claimed in claim 7, further comprising means for
adjusting the charge current frequency as a function of the battery
temperature, the adjustment means being able to control the
determination means such that the battery electrolyte resistance
frequency and the battery charge transfer resistance frequency are
determined again when the temperature changes.
9. The system as claimed in claim 7, wherein the means for
determining the battery electrolyte resistance frequency and the
means for determining the battery charge transfer resistance
frequency each comprise a map of the charge current frequency as a
function of temperature.
10. The system as claimed in claim 7, wherein the means for
determining the battery electrolyte resistance frequency and the
means for determining the battery charge transfer resistance
frequency each comprise a battery impedance spectrography device.
Description
[0001] The technical field of the invention is the control of
charging of batteries of a motor vehicle, and more particularly the
charging of such batteries at low temperatures.
[0002] The performance of a battery (power, energy, durability) is
very sensitive to operating temperature. At low temperature, the
battery has less power, delivers less energy and is subject to
degradation during charging, while at high temperature the battery
has optimum performance in terms of power and energy.
[0003] The following documents are known from the prior art.
[0004] Patent application JP2001037093A discloses the use of a
charge current oscillating at a frequency between 103 Hz and a few
hundred Hz, with an amplitude of a few mV.
[0005] This teaching cannot be applied to Li-Ion batteries insofar
as the specified frequency of 1 kHz is too high. In fact this
frequency corresponds to the inductive part of the impedance
spectrum, or the impedance of the metal parts (i.e. current
collector) and electronic conductive compounds (i.e. conductive
carbon). Furthermore, this patent application mainly describes the
improvement at a constant voltage with a voltage oscillation of the
order of a few mV, which improves the storage performance of the
cell.
[0006] Document U.S. Pat. No. 7,227,336B1 determines the charging
frequency of a battery from a diffusion coefficient.
[0007] Documents FR2943188, FR2964510 and FR2974253 disclose
modulation of the battery charge current. However these documents
do not provide any information concerning the effect of temperature
on the choice of this frequency.
[0008] There is therefore a need for a system and a method for
charging at low temperature which are optimized to reduce the
charging time and the degradation of the battery during
charging.
[0009] An object of the invention is a method for charging a motor
vehicle battery, during which the following steps are used: [0010]
determining the electrolyte resistance frequency of the battery,
[0011] determining the charge transfer resistance frequency of the
battery, and [0012] charging the battery with a current with a
charge current frequency which is higher than the battery
electrolyte resistance frequency and lower than the battery charge
transfer resistance frequency.
[0013] From a complex representation of the impedance as a function
of the charge current frequency, the electrolyte resistance
frequency can be determined as the impedance frequency with a zero
value of its imaginary part and the lowest value of the actual
part, and the charge transfer resistance frequency as the impedance
frequency with a minimal value of its imaginary part and the
highest value of the actual part.
[0014] From a representation of the impedance as a function of the
charge current phase shift, the electrolyte resistance frequency
can be determined as the frequency for which the phase shift is
cancelled out, and the charge transfer resistance frequency as the
frequency for which the derivative of the phase shift as a function
of frequency is cancelled out.
[0015] From a representation of the imaginary part over the cell
impedance as a function of the charge current frequency, the
electrolyte resistance frequency can be determined as the frequency
for which the imaginary part is cancelled out, and the charge
transfer resistance frequency as a frequency for which the
derivative of the imaginary part as a function of frequency is
cancelled out.
[0016] The charge current frequency may lie between 10 Hz and 300
Hz, preferably equal to 100 Hz.
[0017] New battery electrolyte resistance and battery charge
transfer resistance frequencies may be determined when the
temperature changes.
[0018] Another object of the invention is a system for charging a
motor vehicle battery, comprising a means for determining the
electrolyte resistance frequency of the battery, [0019] a means for
determining the charge transfer resistance frequency of the
battery, and [0020] a means for controlling the battery charge
current and able to control the battery charging by a current with
a frequency which is higher than the battery electrolyte resistance
frequency and lower than the battery charge transfer resistance
frequency.
[0021] The system may comprise a means for adjusting the charge
current frequency as a function of the battery temperature, the
adjustment means being able to control the determination means such
that the battery electrolyte resistance frequency and the battery
charge transfer resistance frequency are determined again when the
temperature changes.
[0022] The means for determining the battery electrolyte resistance
frequency and the means for determining the battery charge transfer
resistance frequency may each comprise a map of the charge current
frequency as a function of temperature.
[0023] The means for determining the battery electrolyte resistance
frequency and the means for determining the battery charge transfer
resistance frequency may each comprise a battery impedance
spectrography device.
[0024] Further aims, characteristics and advantages will become
apparent from reading the following description, given solely as a
non-limitative example with reference to the attached drawings, on
which:
[0025] FIG. 1 shows a representation of the impedance in the
complex space as a function of frequency,
[0026] FIG. 2 shows diagrammatically the impedance in the complex
space as a function of frequency,
[0027] FIG. 3 shows a representation of the impedance as a function
of the phase shift,
[0028] FIG. 4 shows a representation of the imaginary part over the
cell impedance as a function of frequency,
[0029] FIG. 5 shows the effects of a current with a frequency equal
to 100 Hz on a battery cell, and
[0030] FIG. 6 shows the development of the phase shift as a
function of frequency at different temperatures.
[0031] The method for controlling the battery charging allows an
improvement in the battery charging at low temperature. The
principle is based on the use of impedance spectroscopy to estimate
the charge current frequency to be applied.
[0032] An impedance spectroscopy may be performed either on board
the vehicle using the method described in the prior art (Impedance
Spectroscopy by Voltage-Step Chronoamperometry Using the Laplace
Transform Method in a Lithium-Ion Battery, Journal of The
Electrochemical Society, 147 (3) 922-929 (2000)) or in advance
using an impedance measurement. Firstly, the impedance spectroscopy
consists of varying the battery charge current frequency while
measuring the impedance of said battery. This gives a variation in
battery impedance as a function of frequency.
[0033] In one case, the impedance spectroscopy performed on board
allows determination of the charging frequency.
[0034] In another case, the charging frequency to be used is
determined and set at the time of design of the charging system, in
order to improve the battery charging under particular
conditions.
[0035] In all cases, the charging frequency is determined from the
impedance spectrum.
[0036] The charging frequency to be used is determined from the
impedance spectrum.
[0037] FIG. 1 is a representation of the impedance in the complex
space as a function of frequency. In other words, FIG. 1 shows a
set of points, the coordinates of which are the imaginary part and
the actual part of the impedance, each point representing a
different frequency of the charge current.
[0038] FIG. 1 also illustrates the variation in impedance of the
battery cell at a temperature of 0.degree..
[0039] On such a representation, we can identify two points
corresponding to characteristic battery charging frequencies.
[0040] The first characteristic point corresponds to an impedance
for which the imaginary part is zero. It is identified on FIG. 1 by
the reference "Frequency 1" and, in the case illustrated by FIG. 1,
corresponds to a frequency of 0.9 kHz. The frequency associated
with this point will be referred to below as the electrolyte
resistance frequency.
[0041] The second characteristic point corresponds to an impedance
for which the imaginary part is minimal for an actual part which is
greater than the actual part of the impedance associated with the
first characteristic point. It is identified on FIG. 1 by the
reference "Frequency 2" and, in the case illustrated in FIG. 1,
corresponds to a frequency of 0.15 Hz. The frequency associated
with this point will be referred to below as the charge transfer
resistance frequency.
[0042] In general, when the impedance frequency of a battery cell
is sampled, successive minima of the imaginary part of the
impedance are detected for increasing values of the actual part of
the impedance. FIG. 2 illustrates such an impedance development
diagrammatically.
[0043] The first minimum of the imaginary part of the impedance
corresponds to the impedance associated with the electrolyte
resistance frequency (i.e. R.sub.electrolyte).
[0044] The last minimum before the diffusion zone corresponds to an
impedance associated with the charge transfer resistance frequency
RCT. We note that the impedance of the charge transfer resistance
is linked by the following equation to the impedance associated
with the electrolyte resistance frequency and to the impedances of
the other minima (marked R.sub.1, R.sub.2 and R.sub.3).
R.sub.electrolyte+R.sub.1+R.sub.2+R.sub.3=RCT
[0045] In the case of an Li-Ion battery, R.sub.1 may be considered
as the resistance of the SEI (solid electrolyte interphase),
R.sub.2 may be the charge transfer resistance of the positive
electrode, and R.sub.3 may be the charge transfer resistance of the
negative electrode (FIG. 2). It is possible to consider there to be
a greater number of RC circuits in series. Thus the charge transfer
resistance frequency RCT will be the sum of these various
contributions. From another aspect, the charge transfer resistance
frequency RCT could be regarded as the frequency just before the
diffusion phenomena, characterized by the diffusion zone more
commonly known as the Warburg zone or Warburg line (FIG. 2).
[0046] Alternatively, the electrolyte resistance frequency and the
charge transfer resistance frequency may be determined as a
function of the phase shift of the voltage at the impedance
terminals relative to the current circulating between the impedance
terminals. FIG. 3 shows a representation of the impedance as a
function of the phase shift. From such a representation, the
electrolyte resistance frequency is determined as the frequency for
which the phase shift is cancelled out, and the charge transfer
resistance frequency as the frequency for which the derivative of
the phase shift as a function of frequency is cancelled out.
[0047] Alternatively, the electrolyte resistance frequency and the
charge transfer resistance frequency may be determined as a
function of the contribution of the imaginary part over the cell
impedance as a function of frequency. FIG. 4 depicts a
representation of the imaginary part over the cell impedance as a
function of frequency. From this representation, the electrolyte
resistance frequency is determined as the frequency for which the
imaginary part is cancelled out, and the charge transfer resistance
frequency as the frequency for which the derivative of the
imaginary part as a function of frequency is cancelled out.
[0048] However, the method must be implemented with minimum
disruption to the voltage measurement allowing determination of the
impedance. It is recalled that the impedance corresponds to the
ratio of voltage over current at the terminals of the element
measured. Thus the higher the impedance modulus at a given
frequency, the more the voltage measurement will vary, making
voltage measurement difficult. This must therefore be taken into
account when selecting the frequency or frequency range to be used.
Thus although the charge transfer resistance frequency is
potentially usable, it has been found that this brings too great a
risk of disrupting the voltage measurement. In contrast, the
electrolyte resistance frequency has the lowest impedance modulus,
but this high frequency may be difficult to control with power
electronics. Similarly, the use of low frequencies may be harmful
since power electronics requires switching at frequencies which may
range from a few Hz to few kHz. Furthermore, the use of a high
frequency will not be of great benefit since, at this frequency,
only the electrolyte will be used, while it is more useful to
mobilize the other parts of the cell for charging, such as the
active material and more particularly the surface of active
materials (i.e. the double layer capacitor).
[0049] Thus a current frequency is preferred which is higher that
the electrolyte resistance frequency (Frequency 1) and lower than
the charge transfer resistance frequency (Frequency 2).
[0050] FIG. 5 illustrates the effects of a current with frequency
equal to 100 Hz on a battery cell.
[0051] Brought to 0.degree. C., a cell was tested by a reference
current 1C. Current 1C corresponds to the current required to
discharge the cell in 1 hour. Another, similar cell was tested with
a sinusoidal current of 2C peak to peak, for a mean current of 37A,
also at a temperature of 0.degree. C. It appears that the use of a
pulsed charge current has a beneficial effect on the capacity
retention (i.e. its useful life). FIG. 6 illustrates the
development of the phase shift as a function of frequency when the
temperature varies. As can be seen, irrespective of battery
temperature the general form of the spectrum and the determination
of the characteristic frequencies remain the same. It is also clear
that the frequency of the charge current develops between 10 Hz and
300 Hz when the temperature varies from 9.degree. C. to -30.degree.
C.
[0052] The charging method also allows an improvement in the life
of graphite-based Li-Ion batteries, and the performance of deeper
charging. It has been found that a pulsed current allows a charging
deeper by the order of 10% or more. This is reflected by a gain in
autonomy of the battery. The depth of charge means the ability to
store a greater or lesser quantity of energy (in Ah) for the same
battery cell. The greater the quantity, the deeper the charge.
[0053] The charging method is applicable to graphite-based Li-Ion
batteries with negative electrode, but also to Li-Ion batteries
based on silicone (Si), germanium (Ge), tin (Sn), titanate in the
form of TiO.sub.2 or Li.sub.4Ti.sub.5O.sub.12, or ternary
carbonated composites based on transition metals and tin. In these
cases, the advantages may be an improvement in life, a shorter
charging time, or an increase in battery autonomy (+10%
capacity).
[0054] The charge current may be of the slot type, triangular,
sinusoidal or other. However observation of the frequency setpoint
takes priority over the current form. The charge current may have
an offset such that it does not pass through a value of zero. It is
however preferred to minimize the continuous current component.
[0055] The charging method allows application of a current with a
periodicity in order to improve the life of the battery, to
increase the depth of charge or to shorten the charging time, while
using a higher mean charging power than when charging the battery
with continuous current, for an identical degradation of the
battery life.
[0056] It is thus possible to choose between a reduction in
charging time and an improvement in life. At equivalent mean
current or mean power, the life is improved by use of a periodic
charging current. A charge with a mean power or mean current that
is higher but periodic gives a degradation of the battery
characteristics equivalent to that observed on charging with a
continuous current.
[0057] The system for charging a motor vehicle battery comprises a
means for determining the battery electrolyte resistance frequency
and a means for determining the battery charge transfer resistance
frequency, connected to a means for controlling the battery charge
current.
[0058] The means for determining the battery electrolyte resistance
frequency and the means for determining the battery charge transfer
resistance frequency each comprise a battery impedance
spectrography device or a map of frequency as a function of
temperature. Alternately, the determination means may share a
single spectrography device.
[0059] The means for controlling the battery charge current is able
to control the battery charging by a current with a frequency which
is higher than the battery electrolyte resistance frequency and
lower than the battery charge transfer resistance frequency.
[0060] The charging system may also comprise a means for adjusting
the charge current frequency as a function of battery temperature.
The adjustment means is able to control the determination means
such that the battery electrolyte resistance frequency and the
battery charge transfer resistance frequency are determined again
when the temperature changes. The new frequencies thus determined
allow determination of a new charge current frequency.
[0061] The charging system may also be deactivated such that the
battery charger functions with a continuous charge current.
[0062] The charging system and method therefore allow determination
of the characteristic frequencies of the battery to be charged, and
determination of the charge current frequency to be used. This
determination is independent of the battery used and allows the
effects of temperature to be taken into account so as to improve
the charge and duration of life of the battery.
* * * * *