Best practices for disassembly and reassembly of solar system with REC Q BMS to add more batteries?

[ThirdEyeSamuel]

I am about to add a second 8S4P Nissan Leaf battery to my system and will need to turn everything off and go through some amount of disconnecting and reconnecting cables.

I'd like to know what the safest methods and best practices in general are for disassembling a system so that I can rewire the REC Q BMS.

I'd also love to know if there is anything specific to REC Q BMS that should be done in a certain order to take it all apart then reassemble with a second battery system.

Thanks in advance
-Samuel

 

[Samsonite801]

Hello, so could you please clarify on the part '...so that I can rewire the REC Q BMS' ?

Because at the beginning you mentioned adding a second 8s4p... Will the new bank have its own BMS, or are you adding all the new cells in p with the original bank or something?

I guess that's why I'm asking, why would it be necessary to rewire the original BMS if you're just adding another whole bank (if it was going to get its own BMS)?

 

[ThirdEyeSamuel]

Hello, so could you please clarify on the part '...so that I can rewire the REC Q BMS' ?

Because at the beginning you mentioned adding a second 8s4p... Will the new bank have its own BMS, or are you adding all the new cells in p with the original bank or something?

I guess that's why I'm asking, why would it be necessary to rewire the original BMS if you're just adding another whole bank (if it was going to get its own BMS)?

I've got more planning to do on the best way to tie in the new battery set but I was thinking I could build an identical second battery and then also wire it to the positive fuse (pre contactor) and the shunt.

I've got to see how REC Q BMS needs it's cell wiring harness configured though.

I've got exactly enough open slots in the current cell balancing wiring harness to add this new 8S4P battery.

Regarding my question I just want to make sure I'm covering all of the best practices for when I power things down to wire up the new battery. I know at the least I'll need to power down the system and unplug the cell balancing wiring harness from REC Q BMS, then wire in the 8x 22ga balancing wires and plug back in after checking for cumulative voltage at each point in the harness.

"Beginning From This Morning" YouTube and blog will probably be a good resource.

 

[Samsonite801]

Biggest thing on that, is make sure to disconnect the harness lead to the BMS for all the balance wires, wire them all up first (to the cells), then plug the harness connector back into the BMS, so you don't risk shorting and frying one of the sense/balance circuits.

Other thing, might be, is some prefer to use a resistor on the inverter to battery connection in series (to charge the caps in the inverter gradually, so they don't get a spark when they hook up the big fat current wire)...

 

[ThirdEyeSamuel]

Biggest thing on that, is make sure to disconnect the harness lead to the BMS for all the balance wires, wire them all up first (to the cells), then plug the harness connector back into the BMS, so you don't risk shorting and frying one of the sense/balance circuits.

Other thing, might be, is some prefer to use a resistor on the inverter to battery connection in series (to charge the caps in the inverter gradually, so they don't get a spark when they hook up the big fat current wire)...

Ok great, thanks for the input, it is much appreciated.

I am indeed aware of making sure to completely wire then plug in the wiring harness from the first install.

Thanks for the tip on reducing the fireworks with the larger battery cables!