I have been building battery systems based on the following batteries.

• Nissan Leaf Battery G2 Lithium Ion 7.5v 66 Ahr LiMn2O4 with LiNiO2 battery pack
• EV-Peak C1-XR 1-6s Lithium 100W 10A AC/DC LiHV Capable Balance Charger 

Leaf Battery information

Discharge curve for a single cellThe battery pack consists of 2 parallel chains of 2 cells in series to give a battery pack voltage of 2 times the nominal voltage of 3.75 to yield 7.5 volts at 66Ahr for a nominal rating of 495 watt/hours.

Two of these battery packs make a battery with a nominal voltage of 15 volts at 66 Ahr to yield 990 watt/hours.

These battery packs can be found used and generally have 60 to 75% of rated capacity.