Multiple battery charge equalizer

Abstract

A charge equalizer for a string of series-connected batteries includes a shunt path for each of the batteries. The equalizer measures the voltage of each of the batteries of the string and then closes a switch in the shunt path associated with the highest voltage battery for a predetermined time. Then the switches of all of the shunt paths are opened and the cycle repeats. In this way, charging is equalized in the batteries of the string, regardless of whether or not any of the batteries of the string is in an over charged condition.

Description

REFERENCE TO MICROFICHE APPENDIX[0001] This specification includes a microfiche appendix consisting of 25 frames included in 1 fiche. This appendix includes copyrighted subject matter, and the assignee of the present invention reserves all copyright rights, other than the right to make facsimile reproductions of the appendix as part of this specification.[0002] This invention relates to methods and systems for equalizing charge on a set of series-connected batteries as the batteries are being charged.[0003] Many automotive electrical systems require a higher operating voltage than that available from the conventional 12.6 V battery. This is because automotive electrical power needs have increased significantly over the past decade, and it is more efficient to supply high power by using a higher voltage rather than by simply increasing the amperage. Operation of such systems requires diligent monitoring and control of the individual battery voltages in order to maintain equal chargin...

AI Technical Summary

Benefits of technology

[0014] The disclosed system reduces charging current applied to the highest-voltage battery, whether or not the highest-voltage battery is in an over charged condition. The undercharged batteries therefore receive relatively more charging current than the batteries at a higher charge state. In this way, the state of charge of the individual batteries is maintained more nearly equal throughout the period that the batteries are being charged to a full state of charge.

Problems solved by technology

Variations between individual batteries within a single string will often cause overcharging or under charging in one or more of the batteries of the string.

The systems described above suffer from the disadvantage that the charging currents applied to individual batteries are only limited after the battery voltage has exceeded a preselected threshold voltage.

For this reason, these systems do not equalize the rate of charging of individual batteries prior to the time any individual one of the batteries reaches the threshold voltage.

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