METHOD FOR DETECTING OF BATTERY CONDITION

• US 20090256524A1
• Filed: 04/09/2009
• Published: 10/15/2009
• Est. Priority Date: 04/11/2008
• Status: Active Grant

• Current Assignee: Furukawa Electric Company Limited
• Original Assignee: Furukawa Electric Company Limited
• Inventors: Nukui, Katsuya
• Granted Patent: US 9,170,304 B2
• Time in Patent Office: Days
• US Class Current: 320/132
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/382 Arrangements for monitoring battery or accumulator variables, e.g. SoC
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: G01R 31/387 Determining ampere-hour charge capacity or SoC
• CPC Class Codes: G01R 31/388 involving voltage measurements
• CPC Class Codes: G01R 31/392 Determining battery ageing or deterioration, e.g. state of health

Abstract

PROBLEM TO BE SOLVED: To provide a method for detecting a charged state of a battery, for evaluating a deterioration thereof due to each of reaction processes that individually have rates of reactions as different from therebetween, and for performing a detection of the charged state of the battery.

SOLUTION: The method for detecting the charged state of the battery according to the present invention comprises the steps of: measuring a voltage V_mes of the battery, an electric current I_mes thereof and a temperature T_mes thereof, and then inputting such the measured values, as a step S1; judging whether or not an absolute value of the measured electric current as the I_mes is smaller than a threshold value of the electric current as an I_thre, as a step S2; estimating an OCV_{20 hr} by making use of an SOCⁿ⁻¹ and an SOHⁿ⁻¹, that are the values after charging and/or discharging at the last time, with reference to a stable OCV estimated formula, as a step S4; calculating a difference between the measured value of the voltage as the V_mes and the OCV_{20 hr}, and then saving such the calculated value, as a step S5; renewing a relaxation function as an Fⁿ(t) with corresponding to an amount of time as t, as processes from a step S6 through a step S19; calculating an SOHⁿ at the step S17 with making use of the Fⁿ(t) to be renewed; and calculating an SOCⁿ at the step S19 with making use thereof.

Claims

1. A method for detecting a charged state of a battery, comprising the steps of:

pre-forming a relaxation function F(t) for calculating a variation of an open circuit voltage (OCV) of the battery after an elapsed time of t since the battery stops charging and/or discharging, as a function of a quantity regarding a predetermined state of the battery;

measuring a variation of the OCV from the OCV at a time of a stable state regarding the battery;

optimizing the relaxation function F(t) with making use of the variation of the OCV to be measured;

estimating the quantity of the state thereof by making use of the relaxation function F(t) to be optimized; and

detecting the charged state of the battery with reference to the quantity of the state thereof to be estimated.

2. The method for detecting the charged state of the battery as defined in claim 1,

wherein the relaxation function F(t) is pre-formed as a function of a temperature of the battery, and

the temperature of the battery is measured and then the same is made used for the relaxation function F(t).

3. The method for detecting the charged state of the battery as defined in claim 1,

wherein a stable OCV estimated formula is pre-formed for calculating the OCV at the time of the stable state thereof, and

the OCV at the time of the stable state thereof is calculated by making use of the stable OCV estimated formula and then a difference between the same and a measured value of the open circuit voltage of the battery is defined to be as the variation of the OCV.

4. The method for detecting the charged state of the battery as defined in claim 3,

wherein the OCV at the time of the stable state thereof is an OCV after an elapsed time of twenty hours since the battery stops charging and/or discharging.

5. The method for detecting the charged state of the battery as defined in claim 1,

wherein the quantity of the state thereof is a state of charge (SOC) and a state of health (SOH) regarding the battery.

6. The method for detecting the charged state of the battery as defined in claim 5,

wherein the battery becomes to be judged as abnormal, in a case where the SOC becomes to be as not higher than a first threshold to be pre-set, or in a case where the SOH becomes to be as not lower than a second threshold to be pre-set.

7. The method for detecting the charged state of the battery as defined in claim 1,

wherein the relaxation function F(t) is expressed as a sum of relaxation functions fi(t) (i=1 to m, i and m are the natural numbers respectively) for every rate of reactions as not less than two (assumed to be as the m terms), that is pre-formed with corresponding to each of the rates of the reactions regarding an inner portion of the battery, and

each of the relaxation functions fi(t) (i=1 to m as the natural numbers respectively) for every rate of the reactions is optimized by dividing the measured value of the variation of the OCV into each of components for individually corresponding to each of the rate of the reactions.

8. The method for detecting the charged state of the battery as defined in claim 7, comprising the additional steps of:

measuring a voltage and an electric current of the battery;

judging for the battery to be that becomes to be stopped charging and/or discharging, by making use of the electric current or of a predetermined signal regarding the stop charging and/or discharging;

calculating a variation of the OCV from the measured value of the voltage, that corresponds to an elapsed time since the battery stops charging and/or discharging;

optimizing each of the relaxation functions fi(t) for every rate of the reactions by making use of the variation of the OCV, that corresponds to each of the rates of the reactions which has a time constant as shorter than the elapsed time;

making use of a relaxation function fi(t) as immediately before regarding the relaxation functions fi(t) for every rate of the reactions, that corresponds to each of the rates of the reactions which has a time constant as longer than the time constant; and

estimating the quantity of the state by making use of the relaxation function fi(t) as immediately before and each of the relaxation functions fi(t) for every rate of the reactions to be optimized.

9. The method for detecting the charged state of the battery as defined in claim 7,

wherein the quantity of the state is calculated by estimating each of the quantity of the states for every rate of the reactions with making use of each of the relaxation functions fi(t) for every rate of the reactions, and by summing up the same.

10. The method for detecting the charged state of the battery as defined in claim 9,

wherein a relaxation function fin(t) for every rate of the reactions after finishing charging and/or discharging at a number of times as an n is expressed as

fin(t)=firef(t)(SOCn/SOCref)(SOHin/SOHiref)g(T)  

 

(Formula

     1),

in a case where the relaxation function fi(t) for every rate of the reactions, the SOC, and the SOH for every rate of reactions, at a reference condition for each thereof, are assumed to be as the firef(t), the SOCref, and the SOHiref respectively, and a dependency for a temperature thereof as the T is assumed to be as G(T) (here, the SOHin is the SOH for every rate of the reactions).

11. The method for detecting the charged state of the battery as defined in claim 10,

wherein the battery becomes to be judged that stops charging and/or discharging in a case where a value of the electric current is measured with which it becomes able to judge for a transient variation in the inner portion of the battery due to the charging and/or the discharging as substantially equivalent to a transient variation at a time of an open circuit therefor.