That's easy to answer, the BMS Battery S12S sine-wave controller;
http://www.bmsbattery.com/controller/552-s06-250w-imitation-torque-square-wave-controller.html
I have a 2WD with basicly the same motor frt. and rear. The frt. controller is an older Infineon square-wave and the rear is the S12S.
The difference between the two is nite and day. The frt. motor is growly and crunchy sounding and the rear is dead silent, seriously. No whine, nothing
But the Infineon is faster because the S12S ramps up very smoothly and it's only a 23 Amp controller. But that's enough for a BPM unless you tackle BIG, long hills.
A bonus to using a new sine-wave controller is it can be mated to the new SLCD-3 display;
This nifty unit gives you all kinds of info. and offers features like;
PAS
Cruise
LVC
and 5 level assist.
This last one lets you pick a speed, set the cruise and pedal along wiyhout holding the throttle :lol:
They kind of get ya on the shipping from China, so look thru the site and order any stuff you might want(think spares too).
MTL34 is putting together a bulk order for next month, which could save you some shipping if you are not in a hurry
BMS Battery has been getting me orders in 7 to 10 business days, pretty good.