Method and device for estimating discharge power of secondary battery

Patent metadata

Field	Value
Publication number	US-10753977-B2
Application number	US-201515308320-A
Country	US
Kind code	B2
Filing date	Sep 22, 2015
Priority date	Oct 1, 2014
Publication date	Aug 25, 2020
Grant date	Aug 25, 2020

Abstract

The present disclosure relates to a method and an apparatus for estimating a discharge power of a secondary battery. The method according to the present disclosure includes setting a state of charge of a secondary battery for which estimation of discharge power is intended, discharging the secondary battery with a plurality of discharge currents while measuring a discharge termination voltage corresponding to each of the discharge currents, generating a current-voltage (I-V) profile that at least forms a point of intersection with the preset discharge boundary condition, and determining a discharge power using a current value and a voltage value corresponding to the point of intersection.

First claim

What is claimed is:

1. A method for estimating discharge power of a lithium secondary battery, comprising:
(a) setting a discharge boundary condition that includes a discharge current upper limit )I limit,max ) and a discharge voltage lower limit (V min ) of the secondary battery;
(b) setting each state of charge among a plurality of states of charge of the secondary battery for which the estimation of the discharge power is intended;
(c) discharging the secondary battery with a plurality of different pulsed discharge currents while measuring a discharge termination voltage corresponding to each of the plurality of different pulsed discharge currents, and generating a current-voltage (I-V) profile for each state of charge among the plurality of states of charge that at least forms a point of intersection with the discharge boundary condition, by using the plurality of different pulsed discharge currents and the corresponding discharge termination voltages, wherein I-V profiles corresponding to the plurality of states of charge increase in non-linearity as the corresponding states of charge decrease;
(d) determining a current value (I) and a voltage value (V) corresponding to the point of intersection as a maximum discharge current (I max ) and a final discharge voltage (V final@Imax ), respectively, wherein the point of intersection is located on V=V min or I=I=I limit,max depending on the state of charge of the secondary battery, and wherein the maximum discharge current (I max ) is lower than a corresponding maximum discharge current (I max,HPPC ) obtained by extrapolation according to a hybrid pulse power characterization (HPPC); and
(e) determining the discharge power corresponding to the state of charge of the secondary battery by using the maximum discharge current and the final discharge voltage.

2. The method of claim 1 , comprising estimating the discharge power according to each state of charge among the plurality of states of charge and a corresponding temperature by repeatedly performing the operations at (b) to (e) with respect to the secondary battery maintained at different temperatures.

3. The method of claim 1 , further comprising determining a resistance corresponding to the state of charge of the secondary battery from a slope of a straight line that connects a Y-intercept of the I-V profile with the point of intersection.

4. The method according to claim 1 , wherein step (c) further comprises:
(c)(1) adjusting the state of charge to one state of charge among the plurality of predetermined states of charge;
(c)(2) setting a discharge current level and discharging the secondary battery for a preset period of time at the discharge current level;
(c)(3) measuring the discharge termination voltage and determining the discharge current level;
(c)(4) in response to the discharge current level and the discharge termination voltage being on the discharge boundary condition, repeating steps (c)(1)-(c)(4) for all remaining states of charge among the plurality of states of charge, and if there are no remaining states of charge, proceed to step (d);
in response to the discharge current level and the discharge termination voltage being out of the discharge boundary condition, restoring the state of charge to the one state of charge and repeating steps (c)(2) to (c)(4), wherein in step (c)(2), the discharge current level being set to a greater value than previously used.

5. An apparatus for estimating discharge power of a lithium secondary battery, comprising:
a storage unit storing therein a resistance look-up table that defines a resistance for each state of charge among a plurality of states of charge, wherein the resistance is determined by using a point of intersection at which a current-voltage (I-V) profile corresponding to each state of charge meets a discharge boundary condition;
a sensor unit configured to measure a discharge current of the secondary battery during discharging of the secondary battery; and
a control unit configured to determine a state of charge of the secondary battery, determine the resistance corresponding to the determined state of charge using the resistance look- up table, and estimate the discharge power of the secondary battery from the determined resistance and the measured discharge current,
wherein I-V profiles corresponding to the plurality of states of charge increase in non-linearity as the corresponding states of charge decrease, such that a maximum discharge current of the secondary battery determined by Hybrid Pulse Power Characterization (HPPC) is greater than an operating current upper limit of the secondary battery.

6. The apparatus of claim 5 , wherein the resistance look-up table is separately defined according to a temperature of the secondary battery,
the sensor unit further measures the temperature of the secondary battery, and
the control unit identifies the resistance look-up table corresponding to the measured temperature, and determines the resistance corresponding to the state of charge by using the identified resistance look-up table.

7. The apparatus of claim 5 , wherein the resistance corresponds to a slope of a straight line that connects the point of intersection with a Y-intercept of the I-V profile.

8. The apparatus of claim 5 , wherein the discharge boundary condition comprises a discharge current upper limit and a discharge voltage lower limit.

9. The apparatus of claim 5 , further comprising the storage unit connected to the control unit, wherein the control unit stores the estimated discharge power into the storage unit.

10. The apparatus of claim 5 , further comprising a display unit connected to the control unit, wherein the control unit displays the estimated discharge power through the display unit.

11. The apparatus of claim 5 , further comprising a communication interface connected to the control unit, wherein the control unit externally transmits the estimated discharge power through the communication interface.

12. An apparatus for estimating maximum discharge power of a lithium secondary battery, comprising:
a storage unit storing therein a maximum discharge power look-up table that defines the maximum discharge power according to each state of charge among a plurality of states of charge, wherein the maximum discharge power is determined from current and voltage at a point of intersection at which a current-voltage (I-V) profile corresponding to each state of charge meets a discharge boundary condition;
a sensor unit configured to measure a discharge current of the secondary battery during discharging of the secondary battery; and
a control unit configured to determine a state of charge of the secondary battery, and determine the maximum discharge power corresponding to the determined state of charge using the maximum discharge power look-up table,
wherein I-V profiles corresponding to the plurality of states of charge increase in non-linearity as the corresponding states of charge decrease, such that a maximum discharge current of the secondary battery determined by Hybrid Pulse Power Characterization (HPPC) is greater than an operating current upper limit of the secondary battery.

13. The apparatus of claim 12 , wherein the maximum discharge power look-up table is separately defined according to a temperature of the secondary battery,
the sensor unit further measures the temperature of the secondary battery, and
the control unit identifies the maximum discharge power look-up table corresponding to the measured temperature, and determines the maximum discharge power by using the identified maximum discharge power look-up table.

14. The

Assignees

• Lg Chemical Ltd

Inventors

• Cha Sun-Young
• Joe Won-Tae

Classifications

• H01M10/48

  Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte (constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569) · CPC title

• G01R31/371

  with remote indication, e.g. on external chargers · CPC title

• G01R31/389

  Measuring internal impedance, internal conductance or related variables · CPC title

• G01R31/3842

  combining voltage and current measurements · CPC title

• G01R31/367 Primary

  Software therefor, e.g. for battery testing using modelling or look-up tables · CPC title