I have an old lead acid which has about 1300 mostly short cycles on it. In daily solar use. Drained 10% charged 5% through winter until it got to 12V with no load. Then I would give it a full charge and a overnight float which the first time seen it through the rest of winter.
By the third year though charging it from 12V the battery would only take 4 Amps at 15V.
A forum (not this one) member suggested to take it down to 11V, gently. Then slap it really hard in the face with whatever voltage it needs to take 10 amps. Do not leave it unattended! It might start slow, but it might pick up fast.
So I did this. Took it down to 11V with minimal < 1 Amp loads and then gave it 16V and it started at 4 Amps and after about 20 minutes rose up to 10A. I kept it on the 10A charge until the voltage across the terminals was 14.40V, then I back the charge voltage back down to 14.50V until it was fully charged, then left it over night on 13.60V.
The idea was to use the high current to try and shake loose some of the sultification and other wear buildup. I don't know how plausible that was, I felt I'd try it as the battery is end of life, maybe I could get another year or more out of it. It did last another 2 years, but that poor old battery is knackered.
I gave it a wee retirement job being a UPS for some 12V network gear. It was fine at it. However when I tested it to see what capacity it had.
From a full charge and an overnight on float it produced 11 Amps at 12V. 12 Amps and it dropped to 11.8V. I gave it as long as it would cope with at 5A down to 12V, then 1A down to 12V. That evening, by bed time, it was sitting at 12.1V having delivered only 11Ah. It's a 100Ah Marine Start battery that is supposed to have 990CCA and 100Ah. Not anymore. In fairness, I got miss sold a "Marine Starter" battery when I asked for a "Marine deep cycle", I did wonder why it was so cheap @~£100. So for a starter battery it did fine, given the life it had.
So many lead acids these days are sold sealed. Not just sealed to help keep maintenance down, but sealed so they cannot be maintained. Even sealed lead acids, especially if they have been "boost" floated for hours in an engine bay repeatedly, they do vent O2 and H2. The water depletes.
Modern SLAs are unrepairable. If the water level drops and shaking the battery you can hear it's half full, the only way in there to refill it, is with a dremel and a chisel. It also suggests they are built to fail long before they will need water. I'm sure big maintainable lead acids exist, but I expect they will cost about twice the consumer mainline will though.
The only blessing is that SLAs are one of the most recycled commodities in the world. Very few people will or are allowed to "land fill" lead.
By the third year though charging it from 12V the battery would only take 4 Amps at 15V.
A forum (not this one) member suggested to take it down to 11V, gently. Then slap it really hard in the face with whatever voltage it needs to take 10 amps. Do not leave it unattended! It might start slow, but it might pick up fast.
So I did this. Took it down to 11V with minimal < 1 Amp loads and then gave it 16V and it started at 4 Amps and after about 20 minutes rose up to 10A. I kept it on the 10A charge until the voltage across the terminals was 14.40V, then I back the charge voltage back down to 14.50V until it was fully charged, then left it over night on 13.60V.
The idea was to use the high current to try and shake loose some of the sultification and other wear buildup. I don't know how plausible that was, I felt I'd try it as the battery is end of life, maybe I could get another year or more out of it. It did last another 2 years, but that poor old battery is knackered.
I gave it a wee retirement job being a UPS for some 12V network gear. It was fine at it. However when I tested it to see what capacity it had.
From a full charge and an overnight on float it produced 11 Amps at 12V. 12 Amps and it dropped to 11.8V. I gave it as long as it would cope with at 5A down to 12V, then 1A down to 12V. That evening, by bed time, it was sitting at 12.1V having delivered only 11Ah. It's a 100Ah Marine Start battery that is supposed to have 990CCA and 100Ah. Not anymore. In fairness, I got miss sold a "Marine Starter" battery when I asked for a "Marine deep cycle", I did wonder why it was so cheap @~£100. So for a starter battery it did fine, given the life it had.
So many lead acids these days are sold sealed. Not just sealed to help keep maintenance down, but sealed so they cannot be maintained. Even sealed lead acids, especially if they have been "boost" floated for hours in an engine bay repeatedly, they do vent O2 and H2. The water depletes.
Modern SLAs are unrepairable. If the water level drops and shaking the battery you can hear it's half full, the only way in there to refill it, is with a dremel and a chisel. It also suggests they are built to fail long before they will need water. I'm sure big maintainable lead acids exist, but I expect they will cost about twice the consumer mainline will though.
The only blessing is that SLAs are one of the most recycled commodities in the world. Very few people will or are allowed to "land fill" lead.
