Mixed up groups of cells in 16s packs and need to reassemble

[BlueSmoke]

Hey guys, I have 4 16s 280 ah packs that I top balanced, drained to about 50%, and put in storage. I taped groups of 4 cells together for easy handling. I was dumb and didn't mark the 4 groups of 4 cells that formed the 16s pack so now I have a mixed up mess.

I need to integrate them into the 80kwh bank that runs my house. Can I just grab 4 groups of cells and put them together in a pack and charge it? I have my inverters set to charge at 56V or 3.5V per cell, so that's pretty conservative. The packs are each managed by an overkill solar BMS.

My big concern is that some blocks of cells may be at 30% and some at 60%. I probably won't be able to tell that with a voltmeter, so I'm just running blind.

I can hook each 4 cell block up to my 12V charger and bring them up before integrating them, but that's a pain. I'm hoping to be lazy. What do you guys think? Be lazy and hope for the best or do it right?

 

[sunshine_eggo]

So you have 64 cells that were all purchased at the same time from the same supplier, same brand and same capacity?

They are all now in unmanaged 4S blocks.

Having done a top balance prior to storage, you guaranteed the need for another top balance. If you can't deploy a battery immediately following the top balance, you shouldn't bother.

Hooking them up to your 12V charger without a 4S BMS could be a great way to destroy one or more in each 4S group if you have a significant cell imbalance. It's almost a certainty that you do.

In that light, I can't see how it matters what blocks went where. You need to repeat the top balance process again. First step is building the 16S battery, installing the 16S BMS and then charging to full. If you can get all cells to the target 3.5V average with all cells over 3.45V without triggering OVP, you got lucky on that one. Go to the next. If you get OVP, time for another top balance.

 

[BlueSmoke]

I have a 4S BMS that I would use to charge each block. I was just hoping to avoid the pain of doing that 16 times!

I have 3 more groups of 16S batteries that I was actively using before storing them marked for about 4 months. Those came back fine when I put them back together. But this obviously isn't the same condition.

 

[HRTKD]

Lazy + LiFePO4 = Lousy Results

Take the time to put together the new batteries. Treat them like they are brand new out of the box.