Different options of wiring 16 cells 280Ah into 24V bank 8s2p

HRTKD

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Thanks, if I DO have 4 BMS across these parallel banks, and I pull the load from the + and - of opposing banks, will these BMS be a limiting factor on the amount of current I can pull from, going to the Quatro?

It depends on how you do it. You might run 2/0 (or whatever is appropriate) from the battery/BMS to a four post bus bar (may be five). Then run a 4/0 cable (again, whatever is appropriate) from the bus bars to the Victron Quattro inverter. I don't think that there will be room to run all four cables from the four batteries directly into the Quattro.

It's likely a bit more complicated than that since a shunt would need to be placed downstream of the bus bar where the four batteries tie into.

Battery negative -> BMS -> negative battery bus bar -> shunt -> common negative bus bar -> inverter
Battery negative -> BMS -> negative battery bus bar -> shunt -> common negative bus bar -> solar charge controller
Battery negative -> BMS -> negative battery bus bar -> shunt -> common negative bus bar -> other stuff
 

Boondock Saint

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I've seen multiple references for using the opposite and diagonal posts recently. One was 2 batteries in parallel, and one was suggested in one of my threads.

If all 4 positives can attach to a busbar and all 4 negatives attach to a busbar, then run leads fron the busbars to the Quatro I'm perfectly fine with that as long as I can terminate a 4/0 into it.
 

HRTKD

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That's not a bad representation of what we're talking about. My only suggestion is to position the lead going to the Quattro in the middle of the bus bar, not at the end.
 

Horsefly

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This is what I'm getting at, pulling the load from opposite poles as suggested.
The "opposite corners" approach is mostly for two parallel strings. The idea is that you have some non-zero resistance cables / buses between the strings, and you want the paths through the strings to have the same amount of cable, so you have the same amount of resistance.

In a 4 string set-up, you really can't make it so the path through all the batteries is the same using that method. The two middle one's will have longer to go for both positive and negative.

If you are using pretty low-resistance bus bars connecting the positives and negatives of the 4 strings, the opposite corners thing is not needed. As @HRTKD said, pull off somewhere in the middle for all four.

If you really want to make sure you have the exact same path length for all four batteries: Have 4 short positive cables, with one going from each positive terminal on the packs to a common terminal block. Then run from that terminal block to your CC and Inverter. Do the same on the negative side.
 

Boondock Saint

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Right on. I have no problem with that at all, to me it makes more sense, but in a scenario where there were two batteries, it was definitely recommended to use opposite battery poles.

Middle it is then! Once more unto the breach!
 

HRTKD

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Some of the configuration ideas of lead acid batteries apply to LiFePO4, some don't. I think the form factor of LiFePO4 makes the configurations different enough that the way we did things with lead acid aren't quite the same with LiFePO4. That said, the general idea that we want to make sure all the batteries have equal access still applies.

I have two 4s LiFePO4 batteries. I tried to keep the 2/0 cables from each battery the same length to ensure that equal access. My cables may be off by 1/2", but you couldn't tell that from the BMS. The number of amps each battery is contributing is usually so close that I stopped worrying about it.
 

Boondock Saint

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The 2/0 to the busbars will be the same length, the 4/0 can be the same too.

I'm considering moving everything inside, right by the bed where the breaker box is. If I put the batteries in the config shown in the diagram, It will fit at the end of the bed. Depending on if I get a decision to go with a Quattro or some MultiPlus units, those too will be within 3-5 feet so really short runs of the 4/0. I'm more concerned about the connection on the input of the Victron than I am about 1/2" difference in cable length on the 4/0.
 
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