Clearly the E bikes don't come with a lithium BMS.
Depends how much you pay. I just converted my pushbike to an E-bike using a kit. I paid more for Samsung cells in the battery and a battery mount and charger that incorporates a battery management system. Some people buy cheap chargers when theirs fail which can lead to thermal runaway. Also some say to extend a lithium batteries life you should charge it to around 85% and discharge it to around 20%. With the occasional full charge to balance the cells. When you charge them they tend to have two phases a quicker early charge but the last little bit takes a lot longer.
Also don't tamper with batteries Which I have been known to ignore. I've replaced the cells in power tool batteries before. Buying Samsung cells and spot welding nickel strips to their ends using a spot welding kit and a car battery as a power source.
