CHARGING METHODS FOR NICKEL-ZINC BATTERY PACKS

• US 20100033138A1
• Filed: 09/21/2007
• Published: 02/11/2010
• Est. Priority Date: 09/21/2006
• Status: Abandoned Application

• Current Assignee: Ethan Alger, Jeffrey Phillips, Richard Bendert, Samaresh Mohanta
• Original Assignee: Ethan Alger, Jeffrey Phillips, Richard Bendert, Samaresh Mohanta
• Inventors: Bendert, Richard, Alger, Ethan, Mohanta, Samaresh, Phillips, Jeffrey
• Application Number:
  US12/442,096
• Publication Number:
  US 20100033138A1
• Time in Patent Office: Days
• US Class Current: 320/153
• CPC Class Codes: H02J 7/0071 with a programmable schedule
• CPC Class Codes: H02J 7/007194 of the battery

Abstract

A temperature compensated constant voltage battery charging algorithm charges batteries quickly and safely. Charging algorithms also include methods to recondition batteries after storage and to correct cell imbalances in a battery pack. A battery charger able to perform these functions is also disclosed.

Claims

1. A method of charging a nickel-zinc battery comprising:

measuring a temperature of the battery,

calculating a calculated voltage based on at least the temperature of the battery,

charging the battery at a constant current until a measured battery voltage reaches the calculated voltage,

charging the battery at the calculated voltage, and

stopping the battery charging at the calculated voltage when an end-of-charge condition is satisfied;

wherein the battery comprises one or more cells.

2. The method of claim 1, wherein the constant current is about 1-2 amps per 2 Amp hour of capacity in the battery.

3. The method of claim 1, wherein the constant current charging operation increases a capacity of the battery to about 80%.

4. The method of claim 1, further comprising:

charging the battery at a corrective current to correct cell imbalance after charging the battery at the calculated voltage.

5. The method of claim 1, further comprising:

charging the battery at a minimum current to maintain charge during period when the battery is not in use and the end-of-charge condition has been satisfied.

6. The method of claim 1, further comprising:

charging the battery at an initial current until a start-of-charge condition is satisfied.

7. The method of claim 4, wherein the corrective current is about 50-200 milliamps per 2 Amp hour of capacity in the battery.

8. The method of claim 5, wherein the minimum current is about 0-50 milliamps per 2 Amp hour of capacity in the battery.

9. The method of claim 6, wherein the initial current is about 0-50 milliamps per 2 Amp hour of capacity in the battery.

10. The method of claim 1, wherein the end-of-charge condition is selected from the group consisting of:

a charging current of less than a defined current associated with a specified state-of-charge;

a lapse of 1.5 hours of charging at the calculated voltage;

a battery temperature increase of 15 degrees Celsius;

a charging current of more than about a defined threshold associated with a short circuit in the battery; and

,

combinations thereof.

11. The method of claim 6, wherein the start-of charge condition is selected from the group consisting of:

(a) a battery temperature of 15 degrees Celsius;

(b) a battery voltage of about 1 volt per cell; and

,

(c) a lapse of about 20 hours or more without meeting either of conditions (a) or (b).

12. The method of claim 1, further comprising

repeating the measuring, and the calculating during the charging.

13. A nickel-zinc battery charger comprising:

an enclosure for holding the nickel-zinc battery,

a thermistor configured to thermally couple to a battery during operation; and

,

a controller configured to execute a set of instructions, the instructions comprising instructions to;

measure a temperature of the battery,

calculate a calculated voltage,

charge the battery at a constant current until a measured battery voltage equals the calculated voltage,

charge the battery at the calculated voltage, and

stop the charge at the calculated voltage when an end-of-charge condition is detected.

14. The battery charger of claim 13, further comprising:

a recondition button and wherein the instructions further comprises

charging the battery at an initial current when the recondition button is pressed.

15. The battery charger of claim 13, wherein the instructions further comprises instructions to

charge the battery at a corrective current.

16. The battery charger of claim 13, wherein the instructions further comprises instructions to

charge the battery at a minimum current.

17. A method of correcting nickel-zinc battery cell imbalance comprising:

providing a battery pack at greater than about 90% state-of-charge in a charger, and

charging the battery at a corrective current for about 30 minutes to 2 hours without limiting the voltage.

18. The method of claim 17, wherein the corrective current is about 50-200 milliamps per 2 Amp hour of capacity in the battery.

19. The method of claim 17, further comprising:

charging the battery at a minimum current until the battery is removed from the charger.

20. The method of claim 19, wherein the minimum current is 0-50 milliamps per 2 Amp hour of capacity in the battery.

21. A method of charging a battery comprising:

measuring a temperature of the battery,

measuring a voltage of the battery,

calculating a calculated voltage based on at least the temperature of the battery,

charging the battery at a charge current until the battery voltage equals the calculated voltage,

reducing the charging current by a defined factor,

charging the battery at the reduced charge current until the battery voltage equals the calculated voltage,

wherein the factor is about 2-10.

22. The method of claim 21, further comprising

repeating the reducing and charging the battery at the reduced charge operations to the same voltage level.

23. A method of charging a nickel-zinc cell, the method comprising:

(a) charging the nickel-zinc battery at a constant current until reaching a point at which (i) the cell'"'"'s state of charge is at least about 70%, (ii) a nickel electrode of the cell has not yet begun to evolve oxygen at a substantial level, and (iii) the cell voltage is between about 1.88 and 1.93 volts; and

(b) charging the nickel-zinc battery at a constant voltage in the range of 1.88-1.93 until an end-of-charge condition is satisfied.

24. The method of claim 23, wherein charging the battery at a constant current is conducted at a current of up to about 4 Amps per 2 Amp hour battery capacity, and wherein the nickel-zinc battery employs an electrolyte having a conductivity of at least about 0.5 cm⁻

1 ohm<sup>−

1</sup>.

25. The method of claim 24, wherein charging the battery at a constant current is conducted until the cell voltage is between about 1.88 and 1.91 volts.