Weak cell issue solved!

[Nadad]

Ok, something like that you have no access to cell-level terminals if it's a sealed up case that you can't just take the lid off of.

If that's the case all you can do non-invasively is an 'equalization' charge where you basically overcharge the rest of the cells in order to bring up the ones that are weak. Depending on how it's done it is somewhere between mildly and severely abusive to the cells which are already fine. But, it is also all you've got, unless you get into some weirder/riskier options. It would be the best option for most people, making the best of a bad situation using only the tools/equipment/knowledge which is already in place.

Battery manufacturer should give guidance on how to do the equalization charge. If their guidelines are followed it should be the case that what you gain by bringing the low cell back into balance, is a lot more than you lose by mildly abusing the rest of your cells. But, if the balance issue quickly reappears and a small number of equalization attempts fails to 'cure' the issue, you are stuck with a 'bad' battery because of one bad cell. And that is the downside of a sealed battery made up of multiple individual cells. One bad apple CAN ruin the bunch.

That is part of why when assembling a large-capacity stationary battery storage array, it's preferable to use a smaller number of individually-packaged cells of very high capacity, vs using a large number of smaller capacity cells which are sealed up in boxes of 6 (12v nominal = 6 cells in series for lead-acid). So for example if you look at Rolls batteries you can buy very large single cells of 2v, smaller 3-cell batteries of 6v, or even smaller 6-cell batteries which are 12v. Using the 12v batteries would minimize the external connections you need to create and maintain, but using the 2v 'batteries' (really just a cell) would maximize your serviceability and make you able to easily balance charge individual cells, or replace bad cells without throwing the rest of the baby out with the bathwater. But yeah, rarely done to make a large storage bank out of individual cells in the lead-acid world, at least for home use. Possible but rare. A lot more likely in the lifepo4 world because those cells aren't flooded with liquid electrolyte so the logistics of making things out of single cells are a lot less onerous without all the liquid issues.

Thanks. I'll learn how to do equalization charge and as you have suggested reach out to the manufacturers for instructions.

 

[Nadad]

I live off grid in Upstate NY. I have a 14400KW solar array, 4x Midnight solar charge controllers, 2x8048 Outback radians and a (1500 A/H, 6000 lbs,) 48 volt BBI "forklift" battery. and a 30KW Isuzu diesel generator

I was having issues with one cell always being 6 points lower (SG 1.22 vs 1.28) than the other 23. I could equalize the battery, but when I did, the other 23 cells would go up to SG 1.3 and hang there for hours waiting for the weak cell to catch up. The other 23 cells got very warm and I would shut down the equalization without truly equalizing. After the EQ was finished?? I'd have 23 cells at 1.29 and 1 cell at 1.26. I was looking for a way to charge the one weak cell at 2.5 to 2.6 Volts DC, without subjecting the other 23 to this voltage. 2.6 vdc applied to a single cell is "Equalize voltage".

Low and behold I found a company called Hindlepower out of Easton PA. They make a single cell battery charger that you can use while the battery is in service.....hooked up and powering your home. I was skeptical, but I bought one. It adjusted it to 2.6 volts / 10 amp output per instruction. Before I actually hooked it up to the weak cell....i thought....."at only 10 amps, this probably wont the moxie to bring the weak cell to 2.6 volts". Anyway, the weak cell was at SG 1.21 at this time and the other 23 were SG 1.25. I hooked it up to the weak cell and I was only getting 2.38 vdc going into the weak cell. I thought I had wasted 465 dollars. I left it charging the weak cell all day long. The test day was partially sunny, but far from clear, as far as solar charging goes. When the sun went down, I checked the SG's and I was shocked. The "weak" cell was now at 1.28 was the other 23 were at 1.27. IT WORKED. I can't honestly say it ever brought the weak cell to 2.6 volts........but I dont care. It did its job. It brought the weak cell inline with the others. That was one week ago and the weak "cell" still runs neck in neck with the other 23. I do think the weak cell is probably a weak cell by definition and will probably have to do this again every month or so (especially in the winter). I wont however, have to subject the other 23 to high temp and high voltage for hours in an attempt to bring the weak cell inline. Hopefully this can help someone out there dealing with a delinquent cell or two.

Single-Cell Charger · HindlePower; Model: BB0442-01. ...........Hindlepower will not sell to us lil guys directly. I bought it thru Dowd Battery in Buffalo NY and paid $465 for it.

Good day, please how are these single cell chargers connected to an FLA?