Battery and methods with real time charge and discharge management

• US 7,940,027 B2
• Filed: 10/19/2007
• Issued: 05/10/2011
• Est. Priority Date: 10/09/2007
• Status: Active Grant

• Current Assignee: SAFT Groupe SA (Totalenergies Se)
• Original Assignee: SAFT Groupe SA (Totalenergies Se)
• Inventors: Barrailh, Gerard, Desprez, Philippe, Benjamin, Sebastien
• Primary Examiner(s): Tso; Edward
• Assistant Examiner(s): WILLIAMS, ARUN C
• Application Number:
  US11/875,575
• Publication Number:
  US 20090091296A1
• Time in Patent Office: 1,299 Days
• Field of Search: 320/134, 324/427
• US Class Current: 320/134
• CPC Class Codes: H01M 10/0525 Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• CPC Class Codes: H01M 10/443 in response to temperature
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A method to manage charge and/or discharge of a rechargeable battery comprising at least one electrochemical cell having predetermined maximum continuous charge current (IMR_C) and/or discharge current (IMD_C) allowed, the method comprising the steps of:

• • measuring an instantaneous charge current (I);
  • defining an overcharge capacity (Cap);
  • determining an instantaneous maximum current allowed in charge (IMR) as a function of the overcharge capacity; and/or
  • defining an over thermal capacity (CapTh);
  • determining an instantaneous maximum pulse current allowed in discharge (IMD_max) as a function of the over thermal capacity.

Claims

1. A method to manage charge of a rechargeable battery comprising at least one electrochemical cell having a predetermined maximum continuous charge current (IMR_C) allowed for given temperature and state of charge conditions, the method comprising the steps of:

measuring in real time the battery current (I);

comparing in real time the battery current (I) to the predetermined maximum continuous charge current (IMR_C);

calculating dynamically an overcharge capacity (Cap),

wherein the value of said overcharge capacity is increased whenever the battery current is less than the predetermined maximum continuous charge current (I<

IMR_C), and

wherein the value of said overcharge capacity is decreased whenever the battery current is more than the predetermined maximum continuous charge current (I>

IMR_C);

determining in real time a value for an instantaneous maximum current allowed in charge (IMR) as a function of the calculated overcharge capacity,

wherein the instantaneous maximum current allowed in charge is equal to the predetermined maximum continuous charge current (IMR_out1=IMR_C) whenever the calculated overcharge capacity is less or equal to zero (Cap≦

0), and

wherein the instantaneous maximum current allowed in charge is more than the predetermined maximum continuous charge current (IMR_out1>

IMR_C) whenever the calculated overcharge capacity is more than zero (Cap>

0).

2. The method of claim 1, wherein as the overcharge capacity (Cap) is calculated as the time integral of the difference between the battery current and the maximum continuous charge current:

Cap=∫

(I−

IMR_c)dt

3. The method of claim 1, wherein the overcharge capacity (Cap) has a maximum value (Cap_max), for a given temperature and state of charge of the battery, defined as the overcharge capacity to allow a pulse charge current of more than the predetermined maximum continuous charge current during a given time without causing accelerated aging of the battery.

4. The method of claim 1, wherein the instantaneous maximum current allowed in charge (IMR) is decreased when the overcharge capacity (Cap) becomes less than a requested value (Cap_req) to allow decrease of the charge current to return to the maximum continuous charge current (IMR_C) with a maximum slope (Islope).

5. The method of claim 1, wherein the instantaneous maximum current allowed in charge (IMR) has a maximum value (IMR_max) defined as a function of a predetermined maximum charge voltage (Vmax) of the battery.

6. The method of claim 1, wherein the instantaneous maximum current allowed in charge (IMR) has a maximum value (IMR_max) comprised between 1.5 to 5 times the predetermined maximum continuous charge current (IMR_C) allowed for given temperature and state of charge conditions.

7. The method of claim 5, wherein the maximum value of the instantaneous maximum current allowed in charge (IMR_max) is reduced when the state of charge (SOC) of the battery increases.

8. The method of claim 1, the battery having a predetermined current allowed in continuous solicitation in charge (IM_therm_nom), the method further comprising the steps of:

calculating dynamically an over thermal capacity (Cap_Therm),

wherein the value of said over thermal capacity is increased whenever the battery current is less than the root mean square current allowed in continuous solicitation in charge (I<

√

IM_therm_nom), and

wherein the value of said over thermal capacity is decreased whenever the battery current is more than the root mean square current allowed in continuous solicitation in charge (I>

√

IM_therm_nom);

determining in real time a second value for the instantaneous maximum current allowed in charge (IM_therm_out) as a function of the calculated over thermal capacity,

wherein said second value of the maximum current allowed in charge is equal to the root mean square of the predetermined current allowed in continuous solicitation in charge (IM_therm_out =√

IM_therm_nom) whenever the calculated over thermal capacity is less or equal to zero (Cap_Therm≦

0), and

wherein said second value of the maximum current allowed in charge is more than the root mean square of the predetermined current allowed in continuous solicitation in charge (IM_therm_out >

√

IM_therm_nom) whenever the calculated over thermal capacity is more than zero (Cap_Therm>

0)

determining an instantaneous maximum current allowed in charge (IMR_out) as the minimum in real time of the value determined as a function of the calculated overcharge capacity and of the value determined as a function of the calculated over thermal capacity (IMR_out=Min[IM_therm_out;

IMR_out1]).

9. The method of claim 8, wherein the over thermal capacity (Cap_Therm) is calculated as the time integral of the difference between the square of the instantaneous charge current and the square of the predetermined maximum continuous charge current,

Cap_Therm=∫

(I²−

IMR_C²)dt

or as the time integral of the square of the difference between the instantaneous charge current and the maximum continuous charge current,

Cap_Therm=∫

(I−

IMR_C)²dt.

10. The method of claim 9, wherein the over thermal capacity (Cap_Therm) is a function of the battery resistance.

11. A method to manage discharge of a battery comprising at least one electrochemical cell having a predetermined maximum continuous discharge current (IMD_C) allowed for given temperature and state of charge conditions, the method comprising the steps of:

measuring in real time the battery current (I);

comparing in real time the battery current (I) to the predetermined maximum continuous discharge current (IMD_C);

calculating dynamically an over thermal capacity (CapTh),

wherein the value of said over thermal capacity is increased whenever the battery current is less than the predetermined maximum continuous discharge current (I<

IMD_C), and

wherein the value of said over thermal capacity is decreased whenever the battery current is more than the predetermined maximum continuous discharge current (I>

IMD_C);

determining in real time an instantaneous maximum current allowed in discharge (IMD_max) as a function of the calculated over thermal capacity,

wherein the maximum current allowed in discharge is equal to the predetermined maximum continuous discharge current (IMD_max=IMD_C) whenever the calculated over thermal capacity is less or equal to zero (CapTh≦

0), and

wherein the maximum current allowed in discharge is more than the predetermined maximum continuous discharge current (IMD_max>

IMD_C) whenever the calculated over thermal capacity is more than zero (CapTh>

0).

12. The method of claim 11, wherein the over thermal capacity is calculated as the time integral of the difference between the square of the battery current and the square of the maximum continuous current allowed in discharge,

CapTh=∫

(I²−

IMD_C²)dt

or as the time integral of the square of the difference between the instantaneous discharge current and the maximum continuous current allowed in discharge,

CapTh=∫

(I−

IMD_C)²dt.

13. The method of claim 12, wherein the over thermal capacity (CapTh) is a function of the battery resistance.

14. The method of claim 11, wherein the over thermal capacity (CapTh) has a maximum value (CapTh_max), for a given temperature and state of charge of the battery, defined as the over thermal capacity to allow a pulse discharge current of more than the predetermined maximum continuous discharge current during a given time without damaging the electrochemical cell by overheating.

15. The method of claim 11, wherein the instantaneous maximum current allowed in discharge (IMD) is decreased when the over thermal capacity (CapTh) becomes less than a requested value (CapTh_req) to allow decrease of the discharge current to return to the maximum continuous discharge current (IMD_C) with a maximum slope (Islope).

16. The method of claim 11, wherein the instantaneous maximum current allowed in discharge (IMD) has a maximum absolute value (IMD_max) defined as a function of a predetermined minimum discharge voltage (Vmin) of the battery.

17. The method of claim 16, wherein the maximum value of the instantaneous maximum current allowed in discharge (IMD_max) is reduced when the state of charge (SOC) of the battery decreases.

18. The method of claim 11, wherein the instantaneous maximum current allowed in discharge (IMD) has a maximum absolute value (IMD_max) comprised between 1.5 to 4 times the predetermined maximum continuous discharge current (IMD_C) allowed for given temperature and state of charge conditions.

19. A controller comprising a memory including a program that manages charge of a rechargeable battery comprising at least one electrochemical cell having a predetermined maximum continuous charge current allowed for given temperature and state of charge conditions, the program of the controller implementing the steps of:

measuring in real time the battery current;

comparing in real time the battery current to the predetermined maximum continuous charge current;

calculating dynamically an overcharge capacity,

wherein the value of said overcharge capacity is increased whenever the battery current is less than the predetermined maximum continuous charge current, and

wherein the value of said overcharge capacity is decreased whenever the battery current is more than the predetermined maximum continuous charge current;

determining in real time a first value of an instantaneous maximum current allowed in charge as a function of the calculated overcharge capacity,

wherein the first value of instantaneous maximum current allowed in charge is equal to the predetermined maximum continuous charge current whenever the calculated overcharge capacity is less or equal to zero, and

wherein the first value of instantaneous maximum current allowed in charge is more than the predetermined maximum continuous charge current whenever the calculated overcharge capacity is more than zero,

wherein the controller limits in real time or provides information allowing to limit in real time the battery current to the determined first value of the maximum current allowed in charge.

20. A battery comprising at least one electrochemical cell, and a charge controller according to claim 19.

21. The battery of claim 20 being a Li-Ion battery.

22. A controller comprising a memory including a program that manages discharge of a rechargeable battery comprising at least one electrochemical cell having a predetermined maximum continuous discharge current (IMD_C) allowed for given temperature and state of charge conditions, the program of the controller implementing the steps of:

measuring in real time the battery current;

comparing in real time the battery current to the predetermined maximum continuous discharge current;

calculating dynamically an over thermal capacity,

wherein the value of said over thermal capacity is increased whenever the battery current is less than the predetermined maximum continuous discharge current, and

wherein the value of said over thermal capacity is decreased whenever the battery current is more than the predetermined maximum continuous discharge current;

determining in real time an instantaneous maximum current allowed in discharge as a function of the calculated over thermal capacity,

wherein the maximum current allowed in discharge is equal to the predetermined maximum continuous discharge current whenever the calculated over thermal capacity is less or equal to zero, and

wherein the maximum current allowed in discharge is more than the predetermined maximum continuous discharge current whenever the calculated over thermal capacity is more than zero,

wherein the controller limits in real time or provides information allowing to limit in real time the battery current to the determined value of the maximum current allowed in discharge.

23. A battery comprising at least one electrochemical cell, and a discharge controller according to claim 22.

24. The battery of claim 23 being a Li-Ion battery.