The controller and motor of my setup are able to handle 72v with a 500A max discharge rate for a peak power output of 36kW. Building a battery that can supply this level of power is no small feat.
The original plan was to use 18650 lithium ion cells that are highly energy dense and able to supply large amounts of current. I designed the pack in a 20s22p configuration for a 72v nominal voltage, 50Ah capacity, and 500A max discharge rate.
18650 Battery Mockup in Frame
These batteries are very energy dense and can be dangerous if not assembled with certain precautions. I researched current methods and planned on using fuses for each cell to isolate any shorts. These fuses would make the pack very safe but would add considerable size, weight, and complexity to the pack. This lead me to search for different battery types.
Lithium iron phosphate batteries are not quite as energy dense as lithium iron batteries, however, their chemistry is extremely stable. This adds an extra layer of safety with thermal runaway being a rarity in this chemistry. The 32700 LiFePO4 battery proved to be a great fit for this project.
32700 Battery Mockup in Frame
The cells shown above are in a 24s10p configuration for a 76.8v nominal voltage, 60Ah capacity, and 600A max discharge rate. The pack will also be balanced with a BMS that has several sensors throughout the battery monitoring temperature. These extra layers of safety are important when dealing with such a large battery.
24s LiFePO4 BMS
I am currently working on the battery and battery box and will continue to update this site as the project continues.