The Lee Hart/TMSI Battery Balancer

The Battery Balancer is a system to keep the batteries in an electric vehicle "balanced". Instead of the wasteful method of simply burning up excess charging energy, the Balancer transfers charge from the stronger/higher capacity modules to the weaker/lower capacity ones so that all batteries will reach empty at the same time during discharge, and will all reach "full" at the same time during charging. It also has auxiliary functions to measure temperatures, voltages, and currents; and to control chargers, heaters and fans to aid in battery management.

It was designed as a research and development tool by Lee Hart for his own EV, but he had additional sets of PCBs made and has made those available to other EV'ers interested in such a device, and who are willing to assemble their own hardware and write their own control software. That's why this website exists; to provide a place for Balancer users to access useful reference material and exchange ideas with others.

The Balancer has has gone through 2 revisions. The original ("Rev A") design, and the improved ("Rev B") design. Both versions are described in more detail below.

Interested parties are encouraged to send me details of their developments and installations, including photos or software if possible, and I will post that material here for the benefit of others.

Thoughts on control strategies or other control software issues are also welcome, as are any modifications you have found worthwhile to the original design.

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Revision History:

18 Feb 2012: Rev A & B overviews updated with links to images of assembled PCBs.
30 Nov 2010: Rev B schematics updated.
01 May 2010: Rev B schematics updated. Rev B overview updated with details of changes.
10 Jan 2010: Rev B schematics updated.
06 Sep 2009: Moved Rev A and B info to their own pages.
05 Apr 2009: Updated with Rev B information.
22 Sep 2002: Added links to bare PCB images.
05 Aug 2002: Initial revision.