We will use these on an electric car race
A123 lifepo4
http://www.rclipos.com/CoDocs/A123_26650.pdf
Max continuous discharge 70A
Pulse discharge at 10 sec 120A
Recommended fast charge current 10A to 3.6V CCCV, 15 min
You can hack them off dewalt packs, or buy them from a guy that already hacked them off a dewalt pack for you.
I bought 12 of them for testing from this guy:
http://myworld.ebay.com/olympics2000888/
They arrived nice and charged, no performance tests yet, but we will be testing them for 4C and 6C charging current and 60-70 amps discharging.
I can post the results when I can.