[EricH]

There is one thing to remember about LiFePO4 batteries, and this will probably affect number and lifetime used. Particularly as you're modifying a vehicle.

They will run at nearly full voltage right up until they're just about discharged (slight decrease, not a whole lot). At which point, the voltage will drop like a rock. If you're using them in a vehicle, you probably want to account for this phenomenon.


Something a little more helpful: When I was doing my senior design project (a robot that could run 10 minutes at a time) we found some 40 A (continuous)/40 Ah LiFePO4s for about $500 for a pair. And, with some digging through some copies of data on that build, I was able to track down our source: http://www.batteryspace.com/12-8v-li...-to-200ah.aspx There are a couple up around $1K; most are $200-$600.