Removable battery for other use?

[0rion]

Hi, rather than building a 4s 280ah battery for my RV, I'm wondering if I could set up 12x 100ah batteries like this:


...since I will occasionally use a trolling motor to go fishing when camping, I though about making one of them removable with an Anderson plug that I could use in the raft.

If I understand it correctly, I'd need to watch my usage when one is removed to not use more than the 200a, which is fine. But when I reconnect the battery, will it cause any issues to the total bank? I'd imagine that when I reconnect it, if the other two are fully charged then their BMS's will shut them down and all of the recharging power will be directed to the third until it's fully charged. Likewise, if it's the end of the day and there's no more solar charge, then my dual purpose battery will probably reach low voltage cutoff first, and the other two will take over the work.

Does this sound right? Anything I'm missing or not considering?

 

[Mike Jordan]

It will not be good to reconnect your trolling batt to the bank after returning, without getting all batts to the same voltage. Preferably all full charge, so the capacity is also the same among the 3

 

[0rion]

I understand the need to keep the cells balanced within a pack, but do different packs also need to be balanced if they have their own BMSs?

 

[0rion]

It will not be good to reconnect your trolling batt to the bank after returning, without getting all batts to the same voltage. Preferably all full charge, so the capacity is also the same among the 3

...Ok, I see it now and not sure why I didn't see it before - connecting the lower power pack back to the bank would cause an inrush of current from the other packs as they'd want to balance. Would probably trip their BMSs. Lost sight that parallel packs work together as a whole.

This electrical stuff is quite a learning curve, and its nice when it 'clicks'.

 

[deeuubee]

It seems doable, but you would want a separate charger to bring it up to the other batteries before reconnecting to the system.
I guess it all depends on whether or not you're on shore power or not.