I am currently using a 48V 450W brushed motor electric bike conversion kit on a 24" mountain bike.
Against all odds, I used 16 x 4500mAh NiMH battery pack to create a 48V 18Ah battery pack as power source.
I know most people uses either AGM or LiFePo4 batteries. I am using NiMH simplily because I have them. Afterall, it isn't that bad using them. You just need a special charger to charge them as NiMH charger for 18Ah or more isn't easily to find.
Once this one break, I will change to 48V 500W chain reduction brushless kit with mud guard.