Comment by jacquesm

The Bosch BMS is a little wonder of engineering, the packs less so. It has a 32 bit NXP CPU, a separate battery managing chip, a bunch of FETs, a DC DC convertor and a battery balancer and whole slew of safety measures (both sw and hw) in a 40 x 60 mm board.

It's one of the most, if not the most impressive BMS I've seen for its size. The packs are a different matter, the engineering of the rear carrier ones is mediocre, the frame mounted ones much better and the PowerTubes are much better still, but far less service friendly.

So far I have not found a way to fool the motor/controller into wanting to play ball with anything other than the genuine article on the other side of the CAN bus.

The battery firmware can be upgraded, but you don't really need to, it just woks. The higher range is not recognized (the battery still reports the Ah capacity of the battery type it shipped with), but the %age state-of-charge is accurate and that's enough to ride by without further monitoring (it's displayed separately, and you have to do a little bit of mental arithmetic to work out how many km you can still go).

There is no loss of efficiency, the batteries are at the same voltage as the originals (and that is something that would instantly cause the BMS to brick itself).