The bike has a giant battery box measuring 160mm x 360mm x 100mm on the inside. For most of the test bikes we used a high output 48v 20ah all cell battery. This battery is expensive...over a $1000 but a very reliable solution. The nice follks at All cell built 10 of these batteries to test our prototypes with. The box is so big that with the right 18650 cells a 48 volt 40ah pack is possible.