Would it be possible to connect 2 Battery packs to 1 BMS?

Lets say you have 2 identical 5p packs laying around. They each have one low quality 30 amp BMS. You could wire the discharge cables together to create a "10p" pack with a effective 60a rating. But you will bypass one or the other bms when charging, which is bad. Among other things; the cons of perma-paralleling 2 packs are well known.

BUT...What if you disconnected the bms from each of the cheap packs and paralleled all of the pack wires together into one high quality/ high amp rating bms? So the 26 sense wires from pack 1 and pack 2 were merged into 13 wires going into the 1 bms. Same for the B+ and B- wires. The sense wires would effectively join the 2 separate 5p groups into 10p groups and any small imbalances would balance through the sense wire, right? Not that I'm thinking about doing this or anything, I haven't even bought the BMS yet..

Yes you can do it, its how I have my 220ah lifepo4 connected. Its basically 4 x 4s10p battery packs connected together in parallel and everything hooked up to 1x 30a 4s bms. As long as you connect all the balance connectors together the pack will equalize. I had it connected that way almost 3 years and never had any problems with it.

Connecting 2x 5p packs to 1x bms would be simpler then what I got.

perhaps relevant
https://endless-sphere.com/forums/viewtopic.php?p=1561188#p1561188

Basically, yes, but: Wiring them permanently into a single pack means if a cell in one dies and takes the rest of it's group with it, it kills all the cells in both packs in that group. Similar failure occurs if the single BMS has a channel that fails and allows either overcharge or overdischarge of a group, and also if the BMS channel fails shorted and kills the cells.


If left as two separate packs with their own BMS, then if one fails for the above reason, you've only lost half your pack, not the whole thing.

If paralleling a pair of packs at the mains only, with BMSes that have just one port (common charge/discharge), then there's no issues with charge or discharge.

If doing that with separate C/D ports, then it is safer to disconnect the charge ports during discharge, and vice-versa.

Ok thanks for the information guys!