Customers have been asking about ebike kits. I am often asked which is best for a folding bike?

Folding bikes are small and compact, adding a large batter and motor changes their portability. Hence most folding bike companies have chosen small front hub motors ( 250w or 350w ) with small light batteries. A rider can always take multiple batteries if necessary. 

Ideally the battery should be be attached low on the bikes to keep the center of gravity low, keeping the bike stable and nimble. The battery should be close to the front hub to minimize complications with wires. Additionally it should be anchored to a stable mount. Overall, a headtube bracket would work perfectly for small, light ebike systems.

Bafang is the largest ebike company in the world, I would look at their offerings before examining completeing brands.