One Cell SG low and falling, what happens next?
Apologies, if this has been discussed and request to be pointed to where I can read about it.
I have a 48 V system, two 6V x 8 battery strings in parallel using Crown CR-235 batteries. System has worked great for almost 4 years. Batteries typically cycle between 80 and 100%, only 4 discharges to between 50 and 60 and one to 50 with triggered auto system cutoff (we left a hose running all night, big well pump cycling and it still ran for 10 hours!). So, these batteries have not been pushed hard routinely and serviced regularly.
I've checked SG periodically and about a year ago I started noticing one cell getting lower. I tried a few equalizes but nothing helped. That cell is down to 1.25 now, adjacent cells in that battery are 1.65 and 1.70 or so and cells in rest of bank typically average 1.75. Battery voltage is 0.05-0.07 V lower than the other batteries in the string.
I am confused why a SG that low is not drawing the voltage down terribly much. And, I need to know what I should expect going forward and when it is necessary to replace the battery to avoid damaging the other batteries.
Technical advice appreciated. Thank you
12 * 300 W (10 fixed rooftop, 2 movable pole mount), Morningstar Tristar MPPT 60, Magnum 4448 PAE, 16 Crown CR-235 6V in two parallel sets of 8 (470 Ah)