Method of estimation of the state of charge of a battery

• US 8,466,685 B2
• Filed: 05/07/2008
• Issued: 06/18/2013
• Est. Priority Date: 05/07/2008
• Status: Expired due to Fees

• Current Assignee: Commissariat a L'Energie Atomique (AES Corporation)
• Original Assignee: Commissariat a L'Energie Atomique (AES Corporation)
• Inventors: Kirchev, Angel Zhivkov
• Primary Examiner(s): Fantu, Yalkew
• Application Number:
  US12/990,299
• Publication Number:
  US 20110043212A1
• Time in Patent Office: 1,868 Days
• Field of Search: 324/427
• US Class Current: 324/427
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/374 with means for correcting the measurement for temperature or ageing
• CPC Class Codes: H01M 10/30 Nickel accumulators H01M10/34 takes precedence
• CPC Class Codes: H01M 10/48 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 Class Codes: H01M 10/486 for measuring temperature
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

The method includes the simultaneous measurement of the current I, of the positive plate potential V₊, and of the temperature T at the positive terminal of the battery, the determination of a temperature compensated value V_c+ of the positive plate potential and the use of the temperature compensated value V_c+ for estimation of the state of charge. This method is more particularly used for estimation of the state of charge of an alkaline battery having a NiOOH positive plate.

Claims

1. A method of estimation of a state of charge of an alkaline battery having a predetermined nominal battery capacity C.sub.n, and comprising a reference electrode and a NiOOH positive plate, said method comprising:

measuring a voltage between said positive plate and said reference electrode, said voltage being representative of the positive plate potential V.sub.+, and estimating the state of charge (SOC) as a function of said positive plate potential and of a battery current, wherein the method comprises;

simultaneous measuring the battery current I, the positive plate potential V.sub.+ and a temperature T at a terminal of the battery, determining a temperature compensated value V.sub.c+ of the positive plate potential as a function of the measured values of the positive plate potential V.sub.+, of the current I, of the temperature T and of the nominal battery capacity C.sub.n, said estimation of the state of charge taking into account the temperature compensated value V.sub.c+ of the positive plate potential, wherein said determination of the temperature compensated value V.sub.c+ of the positive plate potential comprises the following steps;

determining a temperature coefficient k.sub.tsoc corresponding to at least one charge or discharge rate, calculating the compensated value V.sub.c+ of the positive plate potential according to V.sub.c+=V.sub.++(T−

T.sub.0).times.k.sub.tsoc, wherein T.sub.0 is a predetermined reference temperature.

2. The method according to claim 1, wherein the estimation of the state of charge is obtained by means of a first look-up table previously established during a calibration procedure and giving the correspondence between the SOC and the positive plate potential for various charge and discharge rates.

3. The method according to claim 2, wherein the calibration procedure is performed at the reference temperature T₀.

4. The method according to claim 2, wherein, for a given charge or discharge rate, the state of charge values of the first look-up table are calculated by integration of the charge or discharge current during a time interval necessary to obtain a predetermined V₊ value and to a normalization by the discharge battery capacity C_d.

5. The method according to claim 4, wherein the measured charge current values are corrected to take into account the influence of oxygen evolution on the positive plate potential.

6. The method according to claim 1, wherein said temperature coefficient is determined on the basis of an estimation of the state of charge during calibration procedures at different temperatures (T₁, T₂).