Best suited installing the lightweight and compact saddlebag battery. This small 36v 7ah battery can power this bike for at least 20 kilometres per charge, a lot more on flat rail trails.
Using a 250w hub motor (1.6kg), this kit weighs under 3.5kg in total (including battery). The battery can be very easily removed, and weighs less than 2 kg.
Using a 250w mid drive motor (3.2 kg), the weight is a little more, but it is more central and low, on the sprung part of the bike. This motor provides more torque by using the bikes gears to vary performance, much like a manual car.