Method for charging a battery using a constant current adapted to provide a constant rate of change of open circuit battery voltage
View Patent ↗A method for charging a battery is disclosed, wherein a constant current charging current is periodically adjusted as needed such that the change in battery voltage increases approximately linearly during the charging period. In some embodiments the charging is in three phases. An optional first phase charges with a low current until the battery voltages rises to a certain minimum. During a second phase a constant current is provided while the battery voltage is monitored. The second phase constant current is periodically increased if the rate of change of battery voltage is less than a predetermined value and is decreased if the rate of change of battery voltage is more than the predetermined value. When the battery voltage attains a predetermined value, a third phase begins wherein a constant voltage is applied to the battery while the battery current draw is periodically monitored. Charging is stopped when the battery current draw falls to a predetermined value or, in some embodiments, when the charging current drops to a value that is a certain percentage of the charging current at the termination of phase two. In one embodiment the battery voltage is monitored to determine a possible battery failure, for example in the case of the battery voltage decreasing during the constant current charging of phase two. In some embodiments the battery is shorted out in response to detection of a possible failure.
1. A method for charging a battery, wherein the battery includes an enclosure, comprising the steps of:
(a) providing an approximately constant current to the battery;
(b) performing successive sampling operations of a first characteristic of the battery;
(c) in response to the successive sampling operations, determining a one or more parameters of the battery;
(d) comparing the value of the one or more parameters with a first predetermined value;
(e) modifying the value of the approximately constant current supplied to the battery in response to a difference between the value of the one or more parameters and a first predetermined value; and
(f) repeating the method from step (a) until the value of the first characteristic of the battery is determined to be equal to or greater than a second predetermined value.
2. The method according to claim 1 , wherein the first characteristic of the battery is a value of voltage across the battery.
3. The method according to claim 2 , wherein the voltage value is an open circuit voltage value.
4. The method according to claim 1 , wherein the first characteristic of the battery is a value of temperature of the battery enclosure.
5. The method according to claim 1 , wherein the first characteristic of the battery is a value of pressure within the battery enclosure.
6. The method according to claim 1 , wherein the one or more parameters include a rate of change of the value of the first characteristic with respect to time.
7. The method according to claim 1 , wherein the one or more parameters include a rate of change with respect to time of the rate of change of the value of the first characteristic with respect to time.
8. The method according to claim 1 , further comprising the steps of:
(g) providing an approximately constant voltage to the battery;
(h) performing successive sampling operations of a second characteristic of the battery;
(i) repeating the method from step (g) until the value of the second characteristic of the battery is determined to be less than or equal to a third predetermined value.
9. The method according to claim 8 , wherein the second characteristic of the battery is a value of current through the battery.
10. The method according to claim 8 , further comprising an additional step prior to step (g), said additional step comprising storing the instant value of the approximately constant current provided to the battery.
11. The method according to claim 10 , further comprising the step of setting the value of the third predetermined value to a value that is a percentage of the stored instant value of the approximately constant current provided to the battery.
12. The method according to claim 11 , wherein the percentage is ten percent.
13. A method for detecting possible failure of a battery being charged, wherein the battery includes an enclosure, comprising the steps of:
(a) performing successive sampling operations of a characteristic of the battery;
(b) in response to the successive sampling operations, determining a parameter of the battery;
(c) repeating the method from step (a) unless the value of the parameter violates a rule; and
(d) in response to the value of the parameter violating the rule, taking a corrective action.
14. The method according to claim 13 , wherein approximately constant current is provided to said battery, and wherein the characteristic of the battery is a value of voltage across the battery, and the parameter is a change in the value of voltage, and the rule is that the change in voltage cannot be negative.
15. The method according to claim 13 , wherein approximately constant current is provided to said battery, and wherein the characteristic of the battery is a value of voltage across the battery, and the parameter is the rate of change in the value of voltage with respect to time, and the rule is that the rate of change in the value of voltage cannot be negative.
16. The method according to claim 13 , wherein approximately constant voltage is provided to said battery, and wherein the characteristic of the battery is a value of current through the battery, and the parameter is a change in the value of said current, and the rule is that the value of said change cannot be positive.
17. The method according to claim 13 , wherein the taking corrective action comprises stopping the charging operation of the battery.
18. The method according to claim 13 , wherein the taking corrective action comprises activating a means for connecting a positive and a negative terminal of the battery.
19. The method according to claim 18 , wherein said means for connecting comprises a transistor.