These used 18650 Tesla battery modules from a 85kWh Model S. 
 
These are currently the best battery on the market for energy density, allowing many classic conversions to get well over 200 miles per charge. 
 
Model S modules are comprised of 3400mAh cells arranged in a 74p6s configuration. They are rated at 500 amps, 750 amps peak. They have an integrated liquid cooling/heating system, but they can also be air cooled in light duty cycle applications. 
 
They also have an integrated connector with cell level connectivity for BMS systems and two integrated thermistors. The packs contain 444 cells, and each cell is independently safety fused on both terminals. 
 
A preferred configuration for a typical AC50 application is 1p5s for a total of 26kWh, or 2p5s for a total of 53kWh of energy with a total of 10 modules. These work particularly well in 24 volt off grid solar applications as well. 
 
Dimensions:
Length - 27”/685mm
Width (with mounting fins) - 11 13/16”/300mm
Width (without mounting fins) - 11”/280mm
Height - 3”/75mm
Mounting fin at - 2”/50mm
Terminals apart - 9”/230mm
Weight - 55lbs / 25kg
 
Pick up from Oakleigh (Melbourne, Victoria), or can be delivered at buyer cost.