Method for charging or discharging a battery in order to determine the end of charging or discharging on the basis of measurements of current and temperature

• US 8,988,045 B2
• Filed: 10/26/2010
• Issued: 03/24/2015
• Est. Priority Date: 10/29/2009
• Status: Active Grant

• Current Assignee: Commissariat a L'Energie Atomique (AES Corporation)
• Original Assignee: Commissariat a L'Energie Atomique (AES Corporation)
• Inventors: Klein, Jean-Marie, Delaille, Arnaud, Genies, Sylvie
• Primary Examiner(s): Whitmore, Stacy
• Application Number:
  US13/503,557
• Publication Number:
  US 20120212184A1
• Time in Patent Office: 1,610 Days
• Field of Search: 320127-128, 320132-137, 320148-153, 320155-157, 320/159, 320/161, 320/164
• US Class Current: 320/127
• CPC Class Codes: H01M 10/052 Li-accumulators
• CPC Class Codes: H01M 10/443 in response to temperature
• CPC Class Codes: H01M 10/448 End of discharge regulating measures
• CPC Class Codes: H02J 7/00718 in response to charge current gradient
• CPC Class Codes: H02J 7/007194 of the battery
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

The method for charging or discharging a battery comprises measurement of the voltage at the terminals of the battery and comparison of the measured voltage with an end of charging or discharging voltage threshold. The method also comprises measurement of a temperature representative of the temperature of the battery and measurement of the current flowing in the battery to form a pair of measurements. The voltage threshold is then determined according to the pair of measurements. Charging or discharging of the battery is stopped when the voltage threshold is reached.

Claims

1. A method for charging or discharging a battery, the method comprising:

measuring a voltage at terminals of the battery;

measuring a temperature of the battery by a temperature sensor delivering a first value from among N values representative of a range of temperatures;

measuring a current flowing in the battery by a current sensing element delivering a second value from among M values representative of a range of currents;

determining an end of charging voltage threshold or an end of discharging voltage threshold according to a pair of measurements formed by the measured current and the measured temperature;

comparing the measured voltage with the end of charging voltage threshold or with the end of discharging voltage threshold; and

stopping charging or discharging of the battery when the end of charging voltage threshold or the end of discharging voltage threshold is reached,

wherein the end of charging voltage threshold or the end of discharging voltage threshold is supplied by a table with two inputs, a first input being representative of a current value and a second input being representative of a temperature value, the table including N*M voltage values, and further comprising establishing the table by;

filling the table with a set of end of charging voltage thresholds or end of discharging voltage thresholds determined for at least two predefined current values; and

filling the table with the end of charging voltage threshold or the end of discharging voltage threshold by extrapolation from the set of end of charging voltage thresholds or end of discharging voltage thresholds, each extrapolated end of charging voltage threshold or end of discharging voltage threshold is separated from at least one other extrapolated end of charging voltage threshold or end of discharging voltage threshold by a current difference that is equal to a precision of measurement of the current sensing element.

2. The method according to claim 1, wherein the table is predetermined by:

providing a plurality of curves representative of the voltage at the terminals of the battery according to the state of charge of the battery, each curve being established for one pair formed by a fixed temperature of the battery and a fixed current flowing in the battery,

for each curve, determining a voltage value from a state of charge of the battery, and

adding each determined voltage value to the table.

3. The method according to claim 1, wherein when the measured current flowing in the battery is negative, the method is in discharge phase, and discharging is stopped when the voltage at the terminals of the battery becomes lower than or equal to the end of discharging voltage threshold.

4. The method according to claim 1, wherein when the measured current is positive, the method is in charging phase, and charging is stopped when the voltage at the terminals of the battery becomes greater than or equal to the end of charging voltage threshold.

5. The method according to claim 1, further comprising correcting the end of charging voltage threshold or the end of discharging voltage threshold for each pair of measurements, after a first time representative of a period of use of the battery.

6. The method according to claim 5, further comprising:

charging the battery to 100% capacity;

determining an internal resistance value of the battery;

comparing the internal resistance value of the battery with an initial internal resistance value of the battery determined so as to calculate a variation of the internal resistance of the battery; and

correcting all of the end of charging voltage thresholds or the end of discharging voltage thresholds in the table according to the variation of the internal resistance of the battery.

7. The method according to claim 6, wherein the measurement of the initial internal resistance is performed on a new battery charged to 100% capacity.

8. The method according to claim 5, wherein the correction is based on the following formula:

9. The method according to claim 1, further comprising simultaneously measuring the voltage at the terminals of the battery, measuring the current flowing in the battery and measuring the temperature of the battery.

10. The method according to claim 1, wherein the end of charging voltage threshold is defined to stop the charging when a state of charge of the battery is between 75% and 90% of capacity, the end of charging voltage threshold depending on the type of battery.

11. The method according to claim 1, wherein the end of discharging voltage threshold is defined to stop the discharging when a state of charge of the battery is between 20% and 30% of capacity, the end of discharging voltage threshold depending on the type of battery.

12. A method for charging or discharging a battery, the method comprising:

calculating an initial internal resistance of the battery by means of a charge to 100% of capacity;

after a predetermined time of use, charging the battery to 100% of capacity and calculating a new internal resistance of the battery;

calculating a variation of the internal resistance of the battery based on a difference between the initial internal resistance and the new internal resistance;

measuring a voltage at terminals of the battery;

measuring a current flowing in the battery;

measuring a temperature of the battery;

determining an end of charging voltage threshold or an end of discharging voltage threshold according to the measured current, the measured temperature and the variation of the internal resistance of the battery;

comparing the measured voltage with the end of charging voltage threshold or with the end of discharging voltage threshold; and

stopping charging or discharging the battery when the end of charging voltage threshold or the end of discharging voltage threshold is reached.

13. The method according to claim 12, wherein the correction is based on the following formula:

14. The method according to claim 12, wherein the measurement of the initial internal resistance is performed on a new battery charged to 100% capacity.

15. The method according to claim 12, further comprising simultaneously measuring the voltage at the terminals of the battery, measuring the current flowing in the battery and measuring the temperature of the battery.

16. The method according to claim 12, wherein the end of charging voltage threshold is defined to stop the charging when a state of charge of the battery is between 75% and 90% of capacity, the end of charging voltage threshold depending on the type of battery.

17. The method according to claim 12, wherein the end of discharging voltage threshold is defined to stop the discharging when a state of charge of the battery is between 20% and 30% of capacity, the end of discharging voltage threshold depending on the type of battery.

18. The method according to claim 12, wherein the end of charging voltage threshold or the end of discharging voltage threshold is supplied by a table with two inputs, a first input being representative of a current value and a second input being representative of a temperature value.

19. The method according to claim 18, wherein the table is predetermined by:

providing a plurality of curves representative of the voltage at the terminals of the battery according to the state of charge of the battery, each curve being established for one pair formed by a fixed temperature of the battery and a fixed current flowing in the battery;

for each curve, determining a voltage value from a state of charge of the battery; and

adding each determined voltage value to the table.

20. The method according to claim 19, further comprising:

measuring the temperature of the battery by a temperature sensor delivering a first value from among N values representative of a first range of temperature; and

measuring the current flowing in the battery by a current sensing element delivering a second value from among M values representative of a second range of current, wherein the table includes N*M voltage values.

21. The method according to claim 20, further comprising:

establishing the table by;

filling the table with a set of end of charging voltage thresholds or end of discharging voltage thresholds determined for at least two predefined current values; and

filling the table with the end of charging voltage threshold or the end of discharging voltage threshold by extrapolation from the set of end of charging voltage thresholds or end of discharging voltage thresholds, each extrapolated end of charging voltage threshold or end of discharging voltage threshold is separated from at least one other extrapolated end of charging voltage threshold or end of discharging voltage threshold by a current difference that is equal to a precision of measurement of the current sensing element.

22. The method according to claim 12, wherein the measured current flowing in the battery is negative, the method is in discharge phase, and discharging is stopped when the voltage at the terminals of the battery becomes lower than or equal to the end of discharging voltage threshold.

23. The method according to claim 12, wherein the measured current is positive, the method is in charging phase, and charging is stopped when the voltage at the terminals of the battery becomes greater than or equal to the end of charging voltage threshold.