I would have thought it possible, though the Bosch set up probably is a bit more intelligent then a normal system. The system uses I believe more intelligent monitoring charge/discharge system though it should still work if the battery it is reading is 36v irrelevant of the ah.
Would it be any easier to take a parallel connection directly off the controller + & -- directly with a fly lead with inline fuse holder.
For the Swizzbee with it's unusual electronics that is how I wired up a P fly lead sipping power equally from each battery.
You can do it as long as the Bosch battery is active. The normal rules apply, that they have to be the same voltage when you connect and the aux. battery must be disconnected for charging.
What i understand is that the Bosch use only one battery at one time and then periodically switch over batteries. Unlike simpler battery systems the Bosch has some intelligence and recording of information inside the battery packs, so simple paralleled operation would confuse it.. was it charging or discharging when it was being fed with another supply source?
