A little more information in this video;
The best quality batteries and lowest priced batteries for DIY EV's are tier 1 OEM Quality Cells from salvaged (wrecked) EV packs. Two examples are Chevy Volt and Nissan Leaf packs.
Nissan Leaf Module specs are here
Chevy Volt Pack Info - Salvage 16kwh Packs Under $2k here
The cells are rated conservatively by GM at 7.8C, Yabert's tests of Volt packs on the DiyEv car forum suggest a higher C rate, 15+ C!.
$1,400 plus $360 freight. Still over $1k less than new lead!