Battery equalization charging method and apparatus

1. A charging method for equalization charging a battery array consisting of at least two cells, comprising the following steps:

(a) charging the cells of the battery array with a constant charging current;

(b) detecting the cell voltages of the individual cells to judge whether some of the cell voltages have reached a pre-set safe reference voltage;

(c) repeating the step (a) when determining that none of the cell voltages has reached the safe reference voltage, or maintaining at least one of the cell voltages at the safe reference voltage and reducing the charging current at the same time when determining that said at least one of the cell voltages has reached the safe reference voltage, wherein the same charging current flows through all of the cells of the battery array;

(d) judging whether all of the cell voltages have reached the safe reference voltage when the charging current is reduced to a pre-set minimum charging current; and

(e) reducing the charging current continuously below the minimum charging current and then terminating the charging operation when determining that all of the cell voltages have reached the safe reference voltage, or raising the charging current suitably when determining that at least one of the cell voltages has not reached the safe reference voltage.

2. The charging method according to claim 1 , wherein the method further comprises the following steps:

(f) charging the battery array with said raised charging current in a constant current manner;

(g) judging whether all of the cell voltages have reached the safe reference voltage; and

(h) reducing the charging current continuously below the minimum charging current and then terminating the charging operation when determining that all of the cell voltages have reached the safe reference voltage.

3. The charging method according to claim 2 , wherein the step (h) further comprises:

judging whether at least one of the cell voltages has reached a pre-set maximum safe reference voltage when determining that not all of cell voltages have reached the safe reference voltage.

4. The charging method according to claim 3 , wherein the method further comprises the following step:

(i) repeating the step (f) when determining none of the cell voltages has reached the maximum safe reference voltage.

5. The charging method according to claim 4 , wherein the step (i) further comprises:

judging whether at least one of the cell voltages has exceeded the maximum safe reference voltage when determining that at least one of the cell voltages has reached the maximum safe reference voltage.

6. The charging method according to claim 5 , wherein the method further comprises the following step:

(j) reducing said raised charging current to maintain said at least one of the cell voltages which has reached the maximum safe reference voltage at the maximum safe reference voltage and then repeating the step (g) when determining that none of the cell voltages has exceeded the maximum safe reference voltage, and terminating the charging operation forcibly when determining that at least one of the cell voltages has exceeded the maximum safe reference voltage.

7. The charging method according to claim 1 , wherein the method further comprises the following step:

counting the charging time of the whole charging operation and/or several individual stages of the charging operation, and regulating the charging operation forcibly according to the charging condition of the individual cells when the charging time has reached a pre-set charging time threshold value.

8. The charging method according to claim 1 , wherein the method further comprises the following step:

detecting the temperature of the battery array and comparing the detected temperature with a pre-set temperature value, and terminating the charging operation when determining that the detected temperature has exceeded the pre-set temperature value.

9. The charging method according to claim 7 , wherein the method further comprises the following step:

detecting the temperature of the battery array and comparing the detected temperature with a pre-set temperature value, and terminating the charging operation when determining that the detected temperature has exceeded the pre-set temperature value.

10. A charging apparatus for equalization charging a battery array consisting of at least two cells, comprising:

a charging power supply for supplying electric energy to the battery array;

a plurality of voltage signal detection leads; and

a controller which is connected to the charging power supply and is connected to the respective cells of the battery array via the voltage signal detection leads to detect the cell voltages of the respective cells during the charging operation,

wherein a safe reference voltage and a maximum safe reference voltage are pre-set in the controller, and the controller compares the detected cell voltages with the safe reference voltage and the maximum safe reference voltage, to control the charging power supply and in turn control the charging operation according the result of the comparison, and

wherein the control of the controller to the charging power supply comprises:

maintaining at least one of the cell voltages at the safe reference voltage and reducing the charging current at the same time when determining that said at least one of cell voltages has reached the safe reference voltage, wherein the same charging current flows through all of the cells;

commanding the charging power supply to raise the charging current suitably and charge the battery array with said raised charging current when the charging current is reduced to a pre-set minimum charging current and not all of cell voltages have reached the safe reference voltage.

11. The charging apparatus according to claim 10 , wherein the battery array is charged with said raised charging current in a constant current manner.

12. The charging apparatus according to claim 10 , wherein the control of the controller to the charging power supply further comprises:

commanding the charging power supply to reduce the charging current continuously below a pre-set minimum charging current and then terminating the charging operation when determining that all of the cell voltages have reached the safe reference voltage; and

commanding the charging power supply to reduce the charging current to maintain at least one of the cell voltages at the maximum safe reference voltage when determining that said at least one of cell voltages has reached the maximum safe reference voltage.

13. The charging apparatus according to claim 12 , wherein the control of the controller to the charging power supply further comprises:

commanding the charging power supply to terminate the charging operation immediately when determining that at least one of the cell voltages has exceeded the maximum safe reference voltage.

14. The charging apparatus according to claim 10 , wherein the controller further comprises a timer, said timer counts the charging time of the whole charging operation and/or several individual stages of the charging operation, and the controller regulates the charging operation forcibly according to the comparison result between said charging time and a pre-set charging time threshold value.

15. The charging apparatus according to claim 10 , wherein the apparatus further comprises a temperature sensor, said temperature sensor is provided near the battery array to monitor the temperature of the battery array during the charging operation.

16. The charging apparatus according to claim 14 , wherein the apparatus further comprises a temperature sensor, said temperature sensor is provided near the battery array to monitor the temperature of the battery array during the charging operation.

17. The charging method according to claim 1 , wherein the method further comprises the following steps:

(f) charging the battery array with said raised charging current in a pulse current manner;

(g) judging whether all of the cell voltages have reached the safe reference voltage; and

(h) reducing the charging current continuously below the minimum charging current and then terminating the charging operation when determining that all of the cell voltages have reached the safe reference voltage.

18. The charging apparatus according to claim 10 , wherein the battery array is charged with said raised charging current in pulse current manner.