I am still experimenting with ways to balance these cells, but already its clear that they can only be effectively balanced right at the end of charge, or maybe even after the first cell has peaked.

See http://www.terrorhurtz.com/a123/images/DeWaltBalance2.pnghttp://www.terrorhurtz.com/a123/imag...ltBalance2.png

If this pack had been balanced at half-charge, it may have seemed that the pale blue cell was high. But in the last few minutes of charge, it turns out that it is low.

This graph is of the DeWalt charger doing its thing. Notice that all the balancing is done after the first cell has peaked. The first cell is used as a reference to which the others are then matched, which is rather more sophisticated than the other balancers that I have seen. The balancing is done at around 0.15 Amps.

Regarding voltage difference between cells - at peak I would say 0.05V is sufficient. But just before peak, the voltage of the cells is changing rapidly, so achieving less that 0.05V difference at that point is not straightforward.

This graph is a rather extreme example - they would not normally be that far out.

(Message edited by terrorhurtz on July 15, 2007)