Modulated, temperature-based multi-CC-CV charging technique for Li-ion/Li-polymer batteries

• US 8,816,648 B2
• Filed: 08/17/2009
• Issued: 08/26/2014
• Est. Priority Date: 08/17/2009
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Bhardwaj, Ramesh C., Hwang, Taisup, Mank, Richard M.
• Primary Examiner(s): Dunn, Drew A
• Assistant Examiner(s): GRANT, ROBERT J
• Application Number:
  US12/542,411
• Publication Number:
  US 20110037438A1
• Time in Patent Office: 1,835 Days
• Field of Search: 320/152, 320/160, 320/153
• US Class Current: 320/153
• CPC Class Codes: H02J 7/0071 with a programmable schedule

Abstract

Some embodiments of the present invention provide a system that charges a battery. During operation, the system obtains a set of charging currents {I₁, . . . , I_n} and a set of charging voltages {V₁, . . . , V_n}. Next, the system repeats constant-current and constant-voltage charging operations, starting with i=1 and incrementing i with every repetition, until a termination condition is reached. These constant-current and constant-voltage charging operations involve charging the battery using a constant current I_i until a cell voltage of the battery reaches V_i, and then charging the battery using a constant voltage V_i until a charging current is less than or equal to I_i+1.

Claims

1. A method for charging a battery, comprising:

obtaining a set of decreasing charging currents {I₁, . . . , I_n} and increasing charging voltages {V₁, . . . , V_n} by looking up the set of charging currents and voltages in a lookup table based on a measured temperature of the battery, wherein the lookup table includes a different set of charging currents and voltages for each different temperature range to facilitate faster charging at higher temperatures; and

within a single charging cycle, performing a series of two or more constant-current-constant-voltage charging operations O starting with i=1 and incrementing i with every successive operation until a termination condition is reached, wherein each constant-current-constant-voltage charging operation O_i includes,

a constant-current step which involves charging the battery using a constant current I_i until a cell voltage of the battery reaches V_i, and

a constant-voltage step which involves charging the battery using a constant voltage V_i until a charging current is less than or equal to I_i+1.

2. The method of claim 1, wherein looking up the set of decreasing charging currents and the set of increasing charging voltages additionally involves using a battery type of the battery to look up the set of decreasing charging currents and the set of increasing charging voltages.

3. The method of claim 1, wherein the termination condition is reached when the charging current I_i equals a terminal charging current I_term.

4. The method of claim 1, wherein the battery is a rechargeable lithium battery.

5. The method of claim 4, wherein the rechargeable lithium battery is a lithium-polymer battery.

6. The method of claim 4, wherein the rechargeable lithium battery is a lithium-ion battery.

7. The method of claim 6, wherein the lithium-ion battery includes:

a transport-limiting electrode;

an electrolyte;

a separator permeated with the electrolyte; and

a non-transport-limiting electrode.

8. The method of claim 7,

wherein the transport-limiting electrode is a negative electrode;

and

wherein the non-transport-limiting electrode is a positive electrode.

9. A battery with a charging mechanism, comprising:

the battery;

a voltage sensor configured to monitor a cell voltage of the battery;

a current sensor configured to monitor a charging current for the battery;

a charging source configured to apply a charging current and a charging voltage to the battery; and

a controller configured to receive inputs from the voltage sensor and the current sensor, and to send a control signal to the charging source, wherein the controller is configured to,

lookup a set of decreasing charging currents {I₁, . . . , I_n} and increasing charging voltages {V₁, . . . , V_n} in a lookup table based on a measured temperature of the battery, wherein the lookup table includes a different set of charging currents and voltages for each different temperature range to facilitate faster charging at higher temperatures;

charge the battery by performing, a series of two or more constant-current-constant voltage charging operations O within a single charging cycle based on the set of charging currents and voltages, starting with i=1 and incrementing i with every successive operation, until a termination condition is reached;

wherein each constant-current-constant-voltage charging operation O_i includes,

a constant-current step which involves charging the battery using a constant current I_i until a cell voltage of the battery reaches V_i, and

a constant-voltage step which involves charging the battery using a constant voltage V_i until a charging current is less than or equal to I_i+1.

10. The battery of claim 9, wherein the battery further comprises a temperature sensor configured to measure a temperature of the battery.

11. The battery of claim 9, wherein the termination condition is reached when the charging current I_i equals a terminal charging current I_term.

12. The battery of claim 9, wherein the battery is a rechargeable lithium battery.

13. The battery of claim 12, wherein the rechargeable lithium battery is a lithium-polymer battery.

14. The battery of claim 12, wherein the rechargeable lithium battery is a lithium-ion battery.

15. The battery of claim 14, wherein the lithium-ion battery includes:

a transport-limiting electrode;

an electrolyte;

a separator permeated with the electrolyte; and

a non-transport-limiting electrode.

16. The battery of claim 15,

wherein the transport-limiting electrode is a negative electrode;

and

wherein the non-transport-limiting electrode is a positive electrode.

17. A charging mechanism for a battery, comprising:

a voltage sensor configured to monitor a cell voltage of the battery;

a current sensor configured to monitor a charging current for the battery;

a temperature sensor configured to measure a temperature of the battery;

a charging source configured to apply a charging current and a charging voltage to the battery; and

a controller configured to,

receive inputs from the voltage sensor, the current sensor and the temperature sensor

look up a set of decreasing charging currents {I₁, . . . , I_n} and increasing charging voltages {V₁, . . . , V_n} in a lookup table based on the measured temperature of the battery, wherein the lookup table includes a different set of charging currents and voltages for each different temperature range to facilitate faster charging at higher temperatures;

send a control signal to the charging source to perform a series of two or more constant-current-constant-voltage charging operations O_i within a single charging cycle based on the set of charging currents and voltages, starting with i=1 and incrementing i with every successive operation, until a termination condition is reached; and

wherein each constant-current-constant-voltage charging operation O_i includes,

a constant-current step which involves charging the battery using a constant current I_i until a cell voltage of the battery reaches V_i, and

a constant-voltage step which involves charging the battery using a constant voltage V_i until a charging current is less than or equal to I_i+1.

18. The charging mechanism of claim 17, wherein the termination condition is reached when the charging current I_i equals a terminal charging current I_term.

19. The charging mechanism of claim 17, wherein the battery is a rechargeable lithium battery.