I have a RAD City that uses the external battery. Their new models are semi internal in their frame and the keylock is now in the frame. I had to pull the cover on the battery to tighten the charge port jack. I could see the batteries were welded cell to cell and that there is a electronic board installed. I knew at that point that I could have this pack rebuilt when it ages out. Beyond that it turns out that there are battery suppliers that will sell you a mounting bracket for their battery system that can be mounted to the RAD bike if you choose to change. I'm using the RAD box stock electrically and absolutely loving it. I have a 1000 miles on my bike with no issues electronically from any component. Batteries are always a weak point in these types of systems and I expect the battery to age out but I don't know when Build quality on this bike is good and durable. Hope to get a lot of service from this bike