On 12 Sep 2002 at 12:08, Christopher Witmer wrote: > Also, how effective is periodical rotation of cells from the center of the > string to the extremities?
This cannot be done on modern batteries of a type and size usable in EVs. The cells are molded in place in the battery cases, and can't be moved. Nor can the molded plastic battery cases be opened without a great deal of trouble. > > Finally, as long as each cell is monitored and the charge for each cell > carefully controlled, would it be okay to charge each cell individually? It would be ideal to charge each cell individually, but again it is almost impossible to do in modern batteries. The intercell connectors are entirely contained within the battery, and are not accessible from outside the battery. However, it's possible to charge individual ~batteries~ (or modules). In an ideal world this is a great idea. It keeps the pack balanced much better than charging the whole pack as a series string, with less need for equalization. In practice, though, modular charging has been troublesome. Suppose you have a 144 volt pack. If you use modular chargers, typically the reliability of the charging system is one-twelfth that of a series charger. Worse, if one charger fails, you may not know it until you've driven the vehicle and ruined that one uncharged battery. Some combination of a bulk series charger for the entire pack and individual finish chargers for individual batteries might be practicable, but would be expensive. Devices such as the Badicheq, Zivan Smoother, and Lee Hart's Battery Balancer do essentially this. Unfortunately, none of these devices is actually in production. I believe that Lee does supply information on how to homebrew his Battery Balancer, though. David Roden Akron OH USA PS -- Please don't call batteries "cells." It confuses people.
