found this
Prismatic Module Spec:
Nominal Voltage: 7.2V
Nominal Capacity: 6.5Ah
Speceific Power: 1300W/kg
Speceific Energy: 46Wh/kg
Weight: 1040g
from here
http://townhall-talk.edmunds.com/direct/view/.ef2b471/0Battery has better power/weight, and a higher capacity, and by the looks of the picture they would be very easy to stack. The downside is i think they are NiMH or something similar which lose thier max capacity very quickly if they are discharged fully, the prius itself never allows the batterys to fall below 60% charge, which is fine in that application, but not so good for an EV. Although the new plug in prius's will have much better batteries.
But if they are cheap on EBay just use, abuse, and get new ones when they crap out as they would be a cheap and light power source, of which there are very few