How to safely interconnect multiple LiFeP04 batteries that are different types and different brands in one battery bank.

[George Mitchell]

For three years now I have been successfully using multiple 12V LIFeP brands and architectures and different ages in one battery bank. At this point I have 6 100AH LiFePO4 batteries in parallel with no problems:
1) Constant Power w cylindrical cells
2) Relion w cylindrical cells
3) Weize w prismatic cells
4) Weize w prismatic cells
5) Renogy w pouch cells
6) Renogy w pouch cells

What really maters with this is that each of these batteries MUST have the SAME voltage requirements, including max voltage during charge and min voltage during discharge, and the same AH rating, That is essential.
Also essential to prevent disasters is for EACH battery to be fused directly from the positive terminal. The amperage of those fuses must just a bit higher than the maximum discharge from the bank divided by the number of batteries in the bank. These fuses are not for the purpose of protecting the battery they fuse, BUT to protect the rest of the batteries in the bank. This guarantees if any one battery shorts out due to failure, it will blow its on fuse thus not short circuiting the other batteries in the bank.

That said, this bank has experienced two failures recently that stemmed from external failures which were easily repaired. In each of those cases the BMS on each and every one of these 6 batteries functioned perfectly to protect the batteries themselves, very impressive and thus no sign of damage to the batteries. I simply connected the whole bank to two 20 Amp Renogy chargers and the BMS's reset and the bank eventially recharged to the proper voltage without problems. Due to the fact that the failures were caused be external components, I will post that issue seperately and explain the lessons learned in the process.

 

[sunshine_eggo]

This is supplemental, not argumentative.

Contrary to the official opinions of those trying to cover their asses/sell you more batteries, brands/age/cell format don't matter. All LFP work in the same voltage range and are flexible enough to find a happy medium with all of them.

They don't even need to have the same Ah rating. It is not essential. It is helpful, but it is not essential.

What is actually essential is that all batteries in the bank operate within their ratings, preferably sharing current proportional to their share of the total bank capacity.

Link #5 in my signature should be part of everyone's library, and it has a section discussing paralleling batteries.

 

[George Mitchell]

This is supplemental, not argumentative.

Contrary to the official opinions of those trying to cover their asses/sell you more batteries, brands/age/cell format don't matter. All LFP work in the same voltage range and are flexible enough to find a happy medium with all of them.

They don't even need to have the same Ah rating. It is not essential. It is helpful, but it is not essential.

What is actually essential is that all batteries in the bank operate within their ratings, preferably sharing current proportional to their share of the total bank capacity.

Link #5 in my signature should be part of everyone's library, and it has a section discussing paralleling batteries.

I agree with you completely sunshine, and I am actively contemplating adding 200 AH batteries at some point in the future. But I don't want to publicly recommend that until I have some personal experience with it and am able to measure individual battery current flow, and other issues like that. As for my recommendations regarding fusing, I would expect that BMSs would handle that, but I prefer to have back up protection in the form of fuses, just in case something goes wrong. But I appreciate your comment.