BMS (Battery Management System) looks after the battery. Some are crude, others have had more investment in their development. The poorer ones may be good enough - I don't know - but batteries can be fussy and get upset if mis-managed. A good BMS will make sure that the batteries are not charged too fast or too much and balance the charge on all the little cells within the pack. If the designer has taken short cuts, I doubt the battery will last as long but that may not matter for low use. Maybe others have experienced short battery life? My Kalkhoff battery was still sound after 7 years (serviceable).two what is BMS and what whopper of a battery gives you a120 mile range?
Kalkhoff batteries give 125 miles at the lowest level of assistance, on the flat. Those batteries are (or were) £750. Battery capacity is measured in Wh. Kalkhoff were 540Wh. the distance you can go will be roughly in proportion to the Wh of the battery (some systems are more efficient than others). You can supplement a smaller battery by buying a second one, of course. Battery capacity reduces with use (and time) so a 540Wh will become 500Wh after time. I believe that the rate of degradation flattens out after the first couple of years, though.