Here's a link to a article I found which should answer a lot of your questions. I currently have an older 24 volt Currie rear drive kit with lead acid batteries. I find it slow and heavy so I'll be upgrading to a 3000 watt Cyclone mid drive and 48 volt battery. This kit and the 1000 watt Bafang BBSHD mid drive are offered at Luna Cycle. The Cyclone is unrefined raw power and the more civilized BBSHD offers 10 levels of assist. Luna Cycle in California are a good source for quality battery packs and ebike kits. Hope this helps...
https://electricbike-blog.com/2016/0...ot-get-punked/