Title of Invention

METHOD AND APPARATUS FOR QUANTIFYING QUIESCENT PERIOD TEMPERATURE EFFECTS UPON AN ELECTRIC ENERGY STORAGE DEVICE

Abstract A electrical energy storage device may experience quiescent periods of operation. A method is disclosed effective to account for the effects that temperature during quiescent periods has upon the electrical energy storage device.
Full Text GP-307585
METHOD AND APPARATUS FOR QUANTIFYING QUIESCENT PERIOD
TEMPERATURE EFFECTS UPON AN ELECTRIC ENERGY STORAGE DEVICE
TECHNICAL FIELD
[0001] This invention pertains generally to life expectancy of an electrical
energy storage device. More particularly, the invention is concerned with the
effects that periods of rest have upon such life expectancy.
BACKGROUND OF THE INVENTION
[0002] Various hybrid powertrain systems use electrical energy storage
devices to supply electrical energy to electrical machines, which are operable
to provide motive torque, often in conjunction with an internal combustion
engine. One such hybrid powertrain architecture comprises a two-mode,
compound-split, electro-mechanical transmission which utilizes an input
member for receiving power from a prime mover power source and an output
member for delivering power from the transmission to a vehicle driveline.
First and second electric machines, i.e. motor/generators, are operatively
connected to an energy storage device for interchanging electrical power
therebetween. A control unit is provided for regulating the electrical power
interchange between the energy storage device and the electric machines. The
control unit also regulates electrical power interchange between the first and
second electric machines.
[0003] One of the design considerations in vehicle powertrain systems is an
ability to provide consistent vehicle performance and component/system
service life. Hybrid vehicles, and more specifically the battery pack systems
utilized therewith, provide vehicle system designers with new challenges and
tradeoffs. It has been observed that service life of an electrical energy storage
device, e.g. a battery pack system, increases as resting temperature of the
battery pack decreases. However, cold operating temperature introduces
limits in battery charge/discharge performance until temperature of the pack is

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increased. A warm battery pack is more able to supply required power to the
vehicle propulsion system, but continued warm temperature operation may
result in diminished service life.
[0004] Modern hybrid vehicle systems manage various aspects of operation
of the hybrid system to effect improved service life of the battery. For
example, depth of battery discharge is managed, amp-hour (A-h) throughput is
limited, and convection fans are used to cool the battery pack. Ambient
environmental conditions in which the vehicle is operated has largely been
ignored. However, the ambient environmental conditions may have
significant effect upon battery service life. Specifically, same models of
hybrid vehicles released into various geographic areas throughout North
America would likely not result in the same battery pack life, even if all the
vehicles were driven on the same cycle. The vehicle's environment must be
considered if a useful estimation of battery life is to be derived. Additionally,
customer expectations, competition and government regulations impose
standards of performance, including for service life of battery packs, which
must be met.
[0005] End of service life of a battery pack may be indicated by ohmic
resistance of the battery pack. The ohmic resistance of the batter/ pack is
typically flat during much of the service life of the vehicle and battery pack
however, thus preventing a reliable estimate of real-time state-of-life ('SOL')
of the battery pack throughout most of the service life. Instead, ohmic
resistance is most useful to indicate incipient end of service life of the battery
pack.
[0006] Furthermore, service life of a battery pack is affected by resting
temperature, i.e. life of a battery pack system increases as resting temperature
of the battery pack decreases. Therefore a battery pack control system that is
operable to determine a state-of-life of a monitored battery pack would benefit
from a parametric value that is indicative of an effect of temperature of the
battery pack during quiescent or stasis periods. Such quiescent periods occur

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when the battery pack is neither charging nor discharging, e.g. when a hybrid
vehicle using the battery pack is shutdown.
[0007] Therefore, it would be useful to have a method and apparatus which
determines an effect of temperature during a quiescent period on life
expectancy of a battery pack for a hybrid vehicle.
SUMMARY OF THE INVENTION
[0008] A method to determine an effect of temperature during a quiescent
period of an electrical energy storage device operation upon life expectancy of
an electrical energy storage device includes determining a weighted average
temperature of the electrical energy storage device during the quiescent
period. The weighted average temperature is based upon an average
temperature of the electrical energy storage device during the quiescent period
and a temperature of the electrical energy storage device substantially
contemporaneous with the start of the quiescent period. Further, the method
includes determining a resting temperature factor for the electrical energy
storage device based upon the weighted average temperature of the electrical
energy storage device during the quiescent period.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The invention may take physical form in certain parts and
arrangement of parts, an embodiment of which is described in detail and
illustrated in the accompanying drawings which form a part hereof, and
wherein:
[0010] Fig. 1 is a schematic diagram of an exemplary architecture for a
control system and powertrain, in accordance with the present invention;
[0011] Fig. 2 is an algorithmic block diagram, in accordance with the present
invention; and,
[0012] Figs. 3 and 4 are exemplary data graphs, in accordance with the
present invention.

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DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION
[0013] Referring now to the drawings, wherein the showings are for the
purpose of illustrating the invention only and not for the purpose of limiting
the same, Fig. 1 shows a control system and an exemplary hybrid powertrain
system which has been constructed in accordance with an embodiment of the
invention. The exemplary hybrid powertrain system comprises a plurality of
torque-generative devices operable to supply motive torque to a transmission
device, which supplies motive torque to a driveline. The torque-generative
devices preferably comprise an internal combustion engine 14 and first and
second electric machines 56, 72 operable to convert electrical energy supplied
from an electrical storage device (ESD) 74 to motive torque. It is understood
that ESD may include one or more batteries or alternative electrical energy
storage apparatus. The exemplary transmission device 10 comprises a two-
mode, compound-split electro-mechanical transmission having four fixed gear
ratios and two continuously variable operating modes, and includes a plurality
of gears operable to transmit the motive torque to an output shaft 64 and
driveline through a plurality of torque-transfer devices contained therein.
Mechanical aspects of exemplary transmission 10 are disclosed in detail in
U.S. Patent No. 6,953,409, entitled "Two-Mode, Compound-Split, Hybrid
Electro-Mechanical Transmission having Four Fixed Ratios", which is
incorporated herein by reference.
[0014] The control system comprises a distributed control module
architecture interacting via a local area communications network to provide
ongoing control to the powertrain system, including the engine 14, the
electrical machines 56, 72, and the transmission 10.
[0015] The exemplary powertrain system been constructed in accordance
with an embodiment of the present invention. The hybrid transmission 10
receives input torque from torque-generative devices, including the engine 14
and the electrical machines 56, 72, as a result of energy conversion from fuel
or electrical potential stored in electrical energy storage device (ESD) 74. The
ESD 74 typically comprises one or more batteries. Other electrical energy

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storage devices that have the ability to store electric power and dispense
electric power may be used in place of the batteries without altering the
concepts of the present invention. The ESD 74 is preferably sized based upon
factors including regenerative requirements, application issues related to
typical road grade and temperature, and, propulsion requirements such as
emissions, power assist and electric range. The ESD 74 is high voltage DC-
coupled to transmission power inverter module (TPIM) 19 via DC lines
referred to as transfer conductor 27. The TPIM 19 transfers electrical energy
to the first electrical machine 56 by transfer conductors 29, and the TPIM 19
similarly transfer electrical energy to the second electrical machine 72 by
transfer conductors 31. Electrical current is transferable between the electrical
machines 56, 72 and the ESD 74 in accordance with whether the ESD 74 is
being charged or discharged. TPIM 19 includes the pair of power inverters and
respective motor control modules configured to receive motor control
commands and control inverter states therefrom for providing motor drive or
regeneration functionality.
[0016] The electrical machines 56, 72 preferably comprise known
motors/generator devices. In motoring control, the respective inverter
receives current from the ESD and provides AC current to the respective
motor over transfer conductors 29 and 31. In regeneration control, the
respective inverter receives AC current from the motor over the respective
transfer conductor and provides current to the DC lines 27. The net DC
current provided to or from the inverters determines the charge or discharge
operating mode of the electrical energy storage device 74. Preferably,
Motor A 56 and Motor B 72 are three-phase AC electrical machines and the
inverters comprise complementary three-phase power electronic devices.
[0017] The elements shown in Fig. 1, and described hereinafter, comprise a
subset of an overall vehicle control architecture, and are operable to provide
coordinated system control of the powertrain system described herein. The
control system is operable to gather and synthesize pertinent information and
inputs, and execute algorithms to control various actuators to achieve control

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targets, including such parameters as fuel economy, emissions, performance,
driveability, and protection of hardware, including batteries of ESD 74 and
motors 56, 72. The distributed control module architecture of the control
system comprises an engine control module ('ECM') 23, transmission control
module ('TCM') 17, battery pack control module ('BPCM') 21, and the
Transmission Power Inverter Module ('TPIM') 19. A hybrid control module
('HCP') 5 provides overarching control and coordination of the
aforementioned control modules. There is a User Interface ('UP') 13 operably
connected to a plurality of devices through which a vehicle operator typically
controls or directs operation of the powertrain, including the transmission 10.
Exemplary vehicle operator inputs to the UI 13 include an accelerator pedal, a
brake pedal, transmission gear selector, and, vehicle speed cruise control.
Within the control system, each of the aforementioned control modules
communicates with other control modules, sensors, and actuators via a local
area network ('LAN') communications bus 6. The LAN bus 6 allows for
structured communication of control parameters and commands between the
various control modules. The specific communication protocol utilized is
application-specific. By way of example, one communications protocol is the
Society of Automotive Engineers standard J1939. The LAN bus and
appropriate protocols provide for robust messaging and multi-control module
interfacing between the aforementioned control modules, and other control
modules providing functionality such as antilock brakes, traction control, and
vehicle stability.
[0018] The HCP 5 provides overarching control of the hybrid powertrain
system, serving to coordinate operation of the ECM 23, TCM 17, TPIM 19,
and BPCM 21. Based upon various input signals from the UI 13 and the
powertrain, the HCP 5 generates various commands, including: an engine
torque command, clutch torque commands, for various clutches of the hybrid
transmission 10; and motor torque commands, for the electrical machines A
and B, respectively.

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[0019] The ECM 23 is operably connected to the engine 14, and functions to
acquire data from a variety of sensors and control a variety of actuators,
respectively, of the engine 14 over a plurality of discrete lines collectively
shown as aggregate line 35. The ECM 23 receives the engine torque
command from the HCP 5, and generates an axle torque request. For
simplicity, ECM 23 is shown generally having bi-directional interface with
engine 14 via aggregate line 35. Various parameters that are sensed by ECM
23 include engine coolant temperature, engine input speed to the transmission,
manifold pressure, ambient air temperature, and ambient pressure. Various
actuators that may be controlled by the ECM 23 include fuel injectors, ignition
modules, and throttle control modules.
[0020] The TCM 17 is operably connected to the transmission 10 and
functions to acquire data from a variety of sensors and provide command
control signals, i.e. clutch torque commands to the clutches of the
transmission.
[0021] The BPCM 21 interacts with various sensors associated with the ESD
74 to derive information about the state of the ESD 74 to the HCP 5. Such
sensors comprise voltage and electrical current sensors, as well as ambient
sensors operable to measure operating conditions of the ESD 74 including,
e.g., temperature and resistance measured across terminals of the ESD 74 (not
shown). Sensed parameters include ESD voltage, VBAT, ESD current, IBAT, and
ESD temperature, TBAT. Derived parameters preferably include ESD current,
IBAT, ESD internal, RBAT, as may be measured across terminals of the ESD,
ESD state of charge, SOC, and other states of the ESD, including available
electrical power, PBAT_MINand PBAT_MAX.
[0022] The Transmission Power Inverter Module (TPIM) 19 includes the
aforementioned power inverters and motor control modules configured to
receive motor control commands and control inverter states therefrom to
provide motor drive or regeneration functionality. The TPIM 19 is operable
to generate torque commands for machines A and B based upon input from
the HCP 5, which is driven by operator input through UI 13 and system

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operating parameters. Motor torques are implemented by the control
system, including the TPIM 19, to control the machines A and B. Individual
motor speed signals are derived by the TPIM 19 from the motor phase
information or conventional rotation sensors. The TPIM 19 determines and
communicates motor speeds to the HCP 5.
[0023] Each of the aforementioned control modules of the control system is
preferably a general-purpose digital computer generally comprising a
microprocessor or central processing unit, read only memory (ROM), random
access memory (RAM), electrically programmable read only memory
(EPROM), high speed clock, analog to digital (A/D) and digital to analog
(D/A) circuitry, and input/output circuitry and devices (I/O) and appropriate
signal conditioning and buffer circuitry. Each control module has a set of
control algorithms, comprising resident program instructions and calibrations
stored in ROM and executed to provide the respective functions of each
computer. Information transfer between the various computers is preferably
accomplished using the aforementioned LAN 6.
[0024] Algorithms for control and state estimation in each of the control
modules are typically executed during preset loop cycles such that each
algorithm is executed at least once each loop cycle. Algorithms stored in the
non-volatile memory devices are executed by one of the central processing
units and are operable to monitor inputs from the sensing devices and execute
control and diagnostic routines to control operation of the respective device,
using preset calibrations. Loop cycles are typically executed at regular
intervals, for example each 3.125, 6.25, 12.5, 25 and 100 milliseconds during
ongoing engine and vehicle operation. Alternatively, algorithms may be
executed in response to occurrence of an event.
[0025] The action described hereinafter occurs during active operation of the
vehicle, i.e. that period of time when operation of the engine and electrical
machines are enabled by the vehicle operator, typically through a 'key-on'
action. Quiescent periods include periods of time when operation of the
engine and electrical machines are disabled by the vehicle operator, typically

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through a 'key-off action. In response to an operator's action, as captured by
the UI 13, the supervisory HCP control module 5 and one or more of the other
control modules determine required transmission output torque, To.
Selectively operated components of the hybrid transmission 10 are
appropriately controlled and manipulated to respond to the operator demand.
For example, in the exemplary embodiment shown in Fig. 1, when the
operator has selected a forward drive range and manipulates either the
accelerator pedal or the brake pedal, the HCP 5 determines how and when the
vehicle is to accelerate or decelerate. The HCP 5 also monitors the parametric
states of the torque-generative devices, and determines the output of the
transmission required to effect a desired rate of acceleration or deceleration.
Under the direction of the HCP 5, the transmission 10 operates over a range of
output speeds from slow to fast in order to meet the operator demand.
[0026] Referring now to Fig. 2, a schematic diagram is shown,
demonstrating an exemplary method for estimating a state of life of the ESD
74 in real-time, based upon monitored inputs. The method is preferably
executed as one or more algorithms in one of the controllers of the control
system, typically the HCP 5. The estimated state of life of the ESD 74
('SOLK') is preferably stored as a scalar value in a non-volatile memory
location for reference, updating, and for resetting, each occurring at
appropriate points during life of the vehicle and the ESD 74.
[0027] The exemplary method and apparatus to estimate state-of-life
('SOL') of the energy storage device in the hybrid control system in real-time
is disclosed in detail in U.S. Patent Application No. ___/____________,
Attorney Docket No. GP-307586, entitled "Method and Apparatus for Real-
Time Life Estimation of an Electric Energy Storage Device", which is
incorporated herein by reference. The exemplary method and apparatus to
estimate state-of-life comprises an algorithm that monitors in real-time an
ESD current IBAT (in amperes), an ESD temperature TBAT, an ESD voltage VBAT,
an ESD ohmic resistance RBAT, and a ESD State-of -Charge factor ('SOC').
These parameters, IBAT, TBAT, VBAT, and RBAT, are used to determine a

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parametric value for ESD current integrated over time 110, a parametric value
for depth of discharge factor 112, a parametric value for driving temperature
factor 114, and, a parametric value for resting temperature factor TREST 116.
[0028] Each of the aforementioned factors, i.e. the integrated ESD current,
depth of discharge, driving temperature factor, and resting temperature factor,
are combined, preferably by a summing operation shown in block 120 with a
previously determined state of life factor, SOLK, to determine a parametric
value for the SOL, i.e. SOLK+1, which is shown as an output to block 120. The
algorithm to determine the state of life factor, SOLK, is preferably executed
multiple times during each trip (defined as an engine on-off cycle). The
resting temperature factor TREST preferably comprises a derived parametric
value. As described hereinbelow, resting temperature factor TREST 116 is
determined based upon a time-based temperature of the ESD 74 during
quiescent periods of ESD operation. Quiescent periods of ESD operation are
characterized by ESD power flow that is de minimus whereas active periods of
ESD operation are characterized by ESD power flow that is not de minimus.
That is to say, quiescent periods of ESD operation are generally characterized
by no or minimal current flow into or out of the ESD. With respect to an ESD
associated with a hybrid vehicle propulsion system for example, quiescent
periods of ESD operation may be associated with periods of vehicle inactivity
(e.g. powertrain, including electric machines, is inoperative such as during
periods when the vehicle is not being driven and accessory loads are off but
may include such periods characterized by parasitic current draws as are
required for continuing certain controller operations including, for example,
the operations associated with the present invention). Active periods of ESD
operation in contrast may be associated with periods of vehicle activity (e.g.
accessory loads are on and/or the powertrain, including electric machines, is
operative such as during periods when the vehicle is being driven wherein
current flows may be into or out of the ESD).

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[0029] Referring now to Fig. 3, a method and system for determining the
resting temperature factor 116 is now described. The method is preferably
executed as one or more algorithms and associated calibrations in one of the
aforementioned controllers, preferably the HCP 5. The method and system
include determining a temperature of the electrical energy storage device when
the device enters the quiescent period, determining an average temperature of
the electrical energy storage device during the quiescent period, determining a
weighted average temperature of the electrical energy storage device during
the quiescent period based upon the average temperature and the shutdown
temperature; and, determining a parametric value for the resting temperature
factor 116, based upon the weighted average temperature, which is useable to
adjust a life expectancy parameter of the electrical energy storage device.
This is discussed in greater detail hereinbelow.
[0030] Determining temperature of the electrical energy storage device when
the device enters the quiescent period preferably comprises capturing a value
for ESD temperature, TBAT when the vehicle is shutdown by the operator, e.g.
at a key-off event. Determining an average temperature of the electrical
energy storage device during the quiescent period preferably comprises
executing an algorithm to monitor ESD temperature, TBAT at regular intervals
during the quiescent period, and calculating a running average value. Elapsed
time during shutdown is monitored. A weighting factor is determined from
the shutdown temperature, the average temperature, and the elapsed time. The
weighting factor preferably comprises a curve having a nonlinear time decay
based upon temperature of the system, with the decay factor based upon
whether the system is heating or cooling. The weighting factor is determined
by quantity of parametric measurements of temperature used to calculate the
resting temperature factor (block 116). For example, when a large quantity of
temperature samples are taken indicating a long resting time, the parametric
value for resting temperature closely approximates actual temperature, and the
resting temperature factor would comprise a time-average value of the resting
temperature. The weighting factor is applied to the average temperature of the

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ESD during the quiescent period to determine a weighted average temperature
during the quiescent period.
[0031] The resting temperature factor 116, useable for determining the
aforementioned life expectancy parameter SOL of the electrical energy storage
device, is determined based upon the weighted average temperature, as shown
with reference to Fig. 3. Fig. 3 comprises a datagraph having temperature
(degrees, C) as the on the X-axis, and parametric values for resting
temperature factor 116 on the Y-axis. The curve comprises an exponential
function having a nominal value, or zero point, at about 25 C. Establishing the
nominal value for the resting temperature factor at a nominal temperature
value of 25 C is preferable in the exemplary system because life-expectancy
testing and data for the exemplary ESD 74 was conducted at an ambient
temperature of 25 C. Therefore, a parametric value for nominal resting
temperature factor 116 at 25 C is zero, and the parametric value changes for
lower and higher resting temperatures. This includes increasing the resting
temperature factor 116 when the weighted average temperature during the
quiescent period is less than the nominal temperature value of 25 C, and
decreasing the resting temperature factor 116 when the weighted average
temperature during the quiescent period is greater than the nominal
temperature value of 25 C.
[0032] As shown in Fig. 3, the resting temperature factor 116 increases
exponentially with increasing weighted average temperature during the
quiescent period, due to resulting decrease in life expectancy of typical ESD
resulting at higher ambient and higher ESD operating temperatures. The
resting temperature factor 116 decreases exponentially with decreasing
weighted average temperature during the quiescent period, due to resulting
increase in life expectancy of typical ESDs resulting at higher ambient and
higher ESD operating temperatures. Specific calibration values for resting
temperature factors 116 at various temperatures are application-specific, and
depend upon design of the specific ESD, the design life-expectancy of the
ESD, and operating characteristics of the hybrid system utilizing the ESD.

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The resting temperature factor 116 is an element of the control system for the
aforementioned powertrain system.
[0033] Referring now to Fig. 4, an exemplary datagraph is shown for a
specific application, comprising an effect of ESD temperature on the resting
temperature factor. Based upon an elapsed resting time and ESD temperature
during the resting time, a resting temperature factor is determinable. The
plotted lines comprise lines of equal effect, i.e. the lines reflect a
time/temperature relationship that results in a similar change in ESD life. For
example, a short elapsed time at a higher temperature has a similar effect on
ESD life as a longer elapsed time at a lower temperature.
[0034] The invention has been described with specific reference to the
preferred embodiments and modifications thereto. Further modifications and
alterations may occur to others upon reading and understanding the
specification. It is intended to include all such modifications and alterations
insofar as they come within the scope of the invention.

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Having thus described the invention, it is claimed:
1. Method for quantifying an effect of temperature during a quiescent
period of an electrical energy storage device operation upon the electrical
energy storage device, comprising:
determining a weighted average temperature of the electrical energy storage
5 device during the quiescent period based upon an average temperature
of the electrical energy storage device during the quiescent period and
a temperature of the electrical energy storage device substantially
contemporaneous with the start of the quiescent period; and,
determining a resting temperature factor for the electrical energy storage
10 device based upon the weighted average temperature of the device
during the quiescent period.
2. The method of claim 1, wherein determining the resting temperature
factor of the electrical energy storage device during the quiescent period based
upon the weighted average temperature during the quiescent period further
comprises decreasing a previously determined resting temperature factor when
5 the weighted average temperature during the quiescent period is less than a
nominal temperature.
3. The method of claim 2, further comprising exponentially decreasing
the previously determined resting temperature factor based upon a difference
between the weighted average temperature during the quiescent period and the
nominal temperature.
4. The method of claim 1, wherein determining the resting temperature
factor further comprises increasing a previously determined resting
temperature factor when the weighted average temperature during the
quiescent period is greater than a nominal temperature.

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5. The method of claim 4, further comprising exponentially decreasing
the previously determined resting temperature factor based upon a difference
between the weighted average temperature during the quiescent period and the
nominal temperature.
6. The method of claim 1, wherein determining the resting temperature
factor further comprises maintaining the resting temperature factor at a
nominal value when the weighted average temperature during the quiescent
period is substantially equal to a nominal temperature.
7. The method of claim 1, wherein the device comprises a hybrid
powertrain electrical energy storage device and the quiescent period comprises
a period when the hybrid powertrain is disabled.
8. The method of claim 1, wherein the resting temperature factor is
utilized to determine life expectancy of the electrical energy storage device.
9. The method of claim 8, wherein the determined life expectancy of the
electrical energy storage device is utilized in a control system for a hybrid
vehicle.
10. Method for quantifying an effect of temperature during a quiescent
period of an electrical energy storage device operation upon a life expectancy
of an electrical energy storage device, comprising:
determining a weighted average temperature of the electrical energy storage
5 device during the quiescent period based upon an average temperature
of the electrical energy storage device during the quiescent period and
a temperature of the electrical energy storage device substantially
contemporaneous with the start of the quiescent period; and,
determining a change in a state of life parameter based upon the weighted
10 average temperature of the electrical energy storage device.

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11. Apparatus for quantifying an effect of temperature during a quiescent
period of an electrical energy storage device operation upon the electrical
energy storage device, comprising:
a temperature sensor adapted for sensing temperature of the energy storage
5 device;
a computer based controller adapted to receive a signal indicative of sensed
energy storage device temperature;
said computer based controller including a storage medium having a computer
program encoded therein, said computer program comprising:
10 code for determining a weighted average temperature of the electrical
energy storage device during the quiescent period based upon an
average temperature of the electrical energy storage device during
the quiescent period and a temperature of the electrical energy
storage device substantially contemporaneous with the start of the
15 quiescent period; and,
code for determining a resting temperature factor for the electrical
energy storage device based upon the weighted average
temperature of the electrical energy storage device during the
quiescent period.
12. The apparatus of claim 11, wherein code for determining the resting
temperature factor further comprises code for decreasing a previously
determined resting temperature factor when the weighted average temperature
during the quiescent period is less than a nominal temperature.
13. The apparatus of claim 12, wherein the computer program further
comprises code for exponentially decreasing the previously determined resting
temperature factor based upon a difference between the weighted average
temperature during the quiescent period and the nominal temperature.

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14. The apparatus of claim 11, wherein code for determining the resting
temperature factor further comprises code for increasing a previously
determined resting temperature factor when the weighted average temperature
during the quiescent period is greater than a nominal temperature.
15. The apparatus of claim 14, wherein the computer program further
comprises code for exponentially decreasing the previously determined resting
temperature factor based upon a difference between the weighted average
temperature during the quiescent period and the nominal temperature.
16. The apparatus of claim 11, wherein code for determining the resting
temperature factor further comprises code for maintaining the resting
temperature factor at a nominal value when the weighted average temperature
during the quiescent period is substantially equal to a nominal temperature.

A electrical energy storage device may experience quiescent periods of operation. A method is disclosed effective to account for the effects that temperature during quiescent periods has upon the electrical energy storage device.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=zaJ5AwQAukAU80VZsa1UJg==&loc=wDBSZCsAt7zoiVrqcFJsRw==


Patent Number 272302
Indian Patent Application Number 682/KOL/2007
PG Journal Number 14/2016
Publication Date 01-Apr-2016
Grant Date 29-Mar-2016
Date of Filing 04-May-2007
Name of Patentee GM GLOBAL TECHNOLOGY OPERATIONS, INC
Applicant Address 300 GM RENAISSANCE CENTER DETROIT, MICHIGAN
Inventors:
# Inventor's Name Inventor's Address
1 ANTHONY H. HEAP 2969 LESLIE PARK CIRCLE ANN ARBOR, MICHIGAN 48105
2 ANDREW M. ZETTEL 1839 MICHELLE COURT ANN ARBOR, MICHIGAN 48105
PCT International Classification Number G01R31/36
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 11/422,610 2006-06-07 U.S.A.