ELECTROMOTIVE FORCE COMPUTING DEVICE AND STATE OF CHARGE ESTIMATING DEVICE

• US 20080157777A1
• Filed: 12/19/2007
• Published: 07/03/2008
• Est. Priority Date: 12/27/2006
• Status: Active Grant

• Current Assignee: Panasonic EV Energy Company, Limited (Toyota Motor Corporation)
• Original Assignee: Panasonic EV Energy Company, Limited (Toyota Motor Corporation)
• Inventors: Yamabe, Norito
• Granted Patent: US 7,750,640 B2
• Time in Patent Office: Days
• US Class Current: 324/426
• CPC Class Codes: G01R 31/006 on road vehicles, e.g. automobiles or trucks testing of ignition installations peculiar to internal combustion engines F02P17/00
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/374 with means for correcting the measurement for temperature or ageing
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements

Abstract

Error in an electromotive force Ve of a secondary battery calculated on the basis of a polarized voltage Vp is reduced. A polarized voltage computing section acquires multiple data pairs of a current I flowing to the secondary battery and a terminal voltage V of the secondary battery with respect to the current I, calculates an integrated capacity Q by integrating the acquired current I over a predetermined period, computes the polarized voltage Vp of the secondary battery on the basis of the integrated capacity Q, a no-load voltage computing section computes a no-load voltage V0 on the basis of multiple data pairs, a subtracter computes the electromotive force Ve of the secondary battery by subtracting the polarized voltage Vp from the no-load voltage V0, an electromotive force correcting section performs correction with respect to a presently computed electromotive force Ve so that a change amount between a previously computed electromotive force Veb and the presently computed electromotive force Ve does not exceed a predetermined limiting value Vt, and an SOC estimating section estimates the state of charge of the secondary battery on the basis of the post-correction electromotive force Ve′.

Claims

1. An electromotive force computing device comprising:

an electromotive force computing section for computing an electromotive force of a secondary battery with time on the basis of a no-load voltage V0 expressing a terminal voltage of said secondary battery when current flowing to said secondary battery is zero and a polarized voltage Vp of said secondary battery; and

an electromotive force correcting section for correcting an electromotive force Ve so that a change amount does not exceed a predetermined limiting value Vt when said change amount of said electromotive force Ve presently computed with respect to a previously computed electromotive force Veb exceeds said limiting value Vt.

2. An electromotive force computing device according to claim 1, wherein said electromotive force computing section comprising:

a no-load voltage computing section for acquiring over a predetermined period a plurality of data pairs of a current I flowing to said secondary battery and a terminal voltage V of said secondary battery with respect to said current I and computing said no-load voltage V0 from statistical processing on the basis of the acquired plurality of data pairs; and

a polarized voltage computing section for calculating an integrated capacity Q by integrating said current I over said predetermined period and for computing said polarized voltage Vp on the basis of an integrated capacity change amount Δ

Q, which is a difference with a previous integrated capacity Q.

3. An electromotive force computing device according to claim 1, wherein said electromotive force correcting section performs correction by:

adding said limiting value Vt to said electromotive force Veb when said secondary battery is charging; and

subtracting said limiting value Vt from said electromotive force Veb when said secondary battery is discharging.

4. An electromotive force computing device according to claim 1, wherein:

said electromotive force correcting section sets said limiting value Vt with at least one of said electromotive force Veb, change amount Δ

Q of integrated capacity Q of said secondary battery in said predetermined period, battery temperature of said secondary battery, or state of charge of said secondary battery as a parameter.

6. A state of charge estimating device for estimating the state of charge of a secondary battery on the basis of electromotive force of said secondary battery acquired from an electromotive force computing device according to claim 1, wherein:

state of charge of said secondary battery is estimated on the basis of a post-correction electromotive force Ve′

when said change amount of electromotive force exceeds said limiting value Vt; and

state of charge of said secondary battery is estimated on the basis of said electromotive force Ve when said change amount of electromotive force does not exceed said limiting value Vt.

5. An electromotive force computing device comprising:

an electromotive force computing section for computing electromotive force of a secondary battery for which charging or discharging is controlled so that a state of charge is maintained in a predetermined allowable range; and

an electromotive correcting section for correcting said electromotive force Ve so that a change amount of an electromotive force Ve presently computed with respect to an electromotive force Veb previously computed does not exceed a limiting value Vt set in accordance with the state of charge of said secondary battery.