Method for determining the state of charge of rechargeable batteries

• US 20030016023A1
• Filed: 07/10/2002
• Published: 01/23/2003
• Est. Priority Date: 07/11/2001
• Status: Abandoned Application

• Current Assignee: VB Autobatterie GmbH
• Original Assignee: VB Autobatterie GmbH
• Inventors: Richter, Gerolf, Koch, Ingo
• Application Number:
  US10/192,240
• Publication Number:
  US 20030016023A1
• Time in Patent Office: Days
• US Class Current: 324/427
• CPC Class Codes: G01F 1/06 using rotating vanes with tangential admission
• CPC Class Codes: G01F 15/005 Valves valves in general F16K
• CPC Class Codes: G01F 15/18 Supports or connecting means for meters
• CPC Class Codes: G01R 31/379 for lead-acid batteries

Abstract

A method for determining the state of charge of rechargeable batteries by measuring the rechargeable battery voltage and comparing it with predetermined families of characteristic curves, the rechargeable battery voltage U_Bi, the charging time t_Li and, from comparison with characteristic curves ΔQ_i=f(SOC,t_L,U_B) the charge increase are determined in each charging phase. In a subsequent discharge phase, the rechargeable battery voltage U_Bi is measured in time intervals, a rechargeable battery voltage value U_Bij+1 at the end of a time interval is determined from the rechargeable battery voltage U_Bij at the beginning of the time interval by means of an assumed current value I_Bij by comparison with families of characteristic curves U_B=f(I_B,R_i,SOC), and a corrected current value I_Bij+1 is determined by iteration from the deviation of the value thus determined of U_Bij+1 and the rechargeable battery voltage actually measured at the end of the time interval. The loss of charge is calculated from I_Bij+1. During the charging phase and the discharge phase, the rechargeable battery temperature T is measured and the comparison is effected with families of characteristic curves which contain the rechargeable battery temperature T as an additional variable.

Claims

1. A method for determining the state of charge of rechargeable batteries by measuring the rechargeable battery voltage and comparing it with predetermined families of characteristic curves, characterized in that the rechargeable battery voltage U_Bi, the charging time t_Li and, from comparison with characteristic curves Δ

Q₁=f(SOC,t_L,U_B) the charge increase are determined in each charging phase, and in that, in a subsequent discharge phase, the rechargeable battery voltage U_Bi is measured in time intervals, in that a rechargeable battery voltage value U_Bij+1 at the end of a time interval is determined from the rechargeable battery voltage U_Bij at the beginning of the time interval by means of an assumed current value I_Bij by comparison with families of characteristic curves U_B=f(I_B,R_i,SOC), and in that a corrected current value I_Bij+1 is determined by iteration from the deviation of the value thus determined of U_Bij+1 and the rechargeable battery voltage actually measured at the end of the time interval and the loss of charge is calculated from I_Bij+1.

2. The method according to claim 1, characterized in that, during the charging phase and the discharge phase, the rechargeable battery temperature T is measured and the comparison is effected with families of characteristic curves which contain the rechargeable battery temperature T as an additional variable.

3. The method according to claim 1, characterized in that the rechargeable battery voltage drop during the time interval is taken into account in the determination of the rechargeable battery voltage value U_Bij+1.

4. The method according to claim 1, characterized in that the initial value of SOC is determined from the function SOC=f(U_EL,T) by measuring the rechargeable battery voltage U_EL during the transition from discharging to charging.

5. The method according to claim 1, characterized in that the families of characteristic curves are replaced by polynomial equations derived from them.

6. The method according to claim 1, characterized in that the rechargeable battery is a lead acid rechargeable battery.

7. The method according to claim 1, characterized in that the families of characteristic curves are determined empirically.

8. A method for determining the state of charge of a rechargeable battery comprising:

measuring rechargeable battery voltage U_Bi at a selected charging time t_Li in each charging phase;

determining charge increase by comparing battery voltage U_Bi with characteristic curves Δ

Q_i=f(SOC,t_L,U_B);

measuring rechargeable battery voltage U_Bi at selected time intervals in a subsequent discharge phase;

determining a rechargeable battery voltage value U_Bij+1 at the end of a selected time interval from a rechargeable battery voltage U_Bij at the beginning of the selected time interval from an assumed current value I_Bij by comparison with families of characteristic curves U_B=f(I_B,R_i,SOC);

determining a corrected current value I_Bij+1 by iteration from deviation of a value determined for U_Bij+1 and battery voltage actually measured at the end of the time interval; and

calculating the loss of charge from I_Bij+1.

9. The method according to claim 8, wherein, during the charging phase and the discharge phase, the rechargeable battery temperature T is measured and the comparison is effected with families of characteristic curves which contain the rechargeable battery temperature T as an additional variable.

10. The method according to claim 8, wherein the rechargeable battery voltage drop during the selected time interval is taken into account in determining the rechargeable battery voltage value U_Bij+1.

11. The method according to claim 8, wherein an initial value of SOC is determined from SOC=f(U_EL,T) by measuring rechargeable battery voltage U_EL during a transition from discharging to charging.

12. The method according to claim 8, wherein the families of characteristic curves are replaced by polynomial equations derived therefrom.

13. The method according to claim 8, wherein the rechargeable battery is a lead acid rechargeable battery.

14. The method according to claim 8, wherein the families of characteristic curves are determined empirically.