Aaron, An idea I got from someone from the visforvoltage forum is to build a hybrid battery pack. That way you get good attributes from both battery technologies without having to spend too much if one is lead-acid.
For example, Chinese NiMH D cells<http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=710>offer pretty good energy storage for the money. The down side is that they can only peak 3C and have a high internal resistance. But if you keep the discharge rate at 1C, they'll probably work very well. A way to do this is to have a 30-50 ah lead-acid pack, then two or three strings of D cells at 5-10v higher than your lead-acid pack. After you ride a mile, switch in the NiMH cells in parallel with the lead-acid pack, and they will charge it and also help to lower the discharge rate, thus allowing for more total energy out of the lead-acid pack. You will need special NiMH chargers for the D cell strings, and you will need to charge one string, or even half a string separately, so you may need quite a few chargers. You could do this with Saft cells too: http://www.batteryspace.com Another place to find Chinese D cells: http://www.all-battery.com Good luck, Andrew
