I got myself a 600w charger CT600 brand under a kilogram and as big as the original charger if not smaller I think the amps where set to 8 or 10A and I would say as well the maximum is around 12A.

I have the TS and charged the original battery that way. Now I can charge 30-35A if I want because I build my own system. Charger is about the size of a normal server rack power supply and weights about 2kg and can give out 3kw charge per hour maximum. I don't use original battery. 

I use 74,5 v fully charged battery on original controller shunt modded. power is 0-84km/h and uphill is and can be the same speed short of a few km/h from top speed.

Shunt mod may trip original automatic reusable fuse so beware.