Sad that the original manufacturer of Li-ion batteries in the early 1990's has to divest itself of battery division:
http://insideevs.com/japanese-government-urges-nissan-to-purchase-sonys-lithium-ion-battery-division/" onclick="window.open(this.href);return false;
Here are two articles from EE Times Design that covers the generic topic of cell balancing.
12/8/11 - "Balance hybrid/EV battery packs to extend operational lifetime: Pt. 1—Hardware and strategy"...
