Nathan Barnard
New Member
- Joined
- Sep 14, 2021
- Messages
- 22
Looking for advise on matching and/or removing weaker batteries to maintain this battery pack.
I've been using it as is for the last two years. I has been performing well with daily discharges of 500-600ah @24v, it has stayed balanced up until recently. The lower side is dropping off much quicker than upper side. I regularly pull 250amps from it (for electric oven or clothes dryer) and charge around 100amps with solar.
Yesterday I charged both sides up to 14.2v and held them there overnight, then this morning I disassembled and tested each battery on a digital CCA load tester, marking down the cranking amps and internal resistance. I put it in a spreadsheet to try to figure out which batteries I should switch to balance average resistance and CA on pack (so they would discharge and recharge equally). I'm not sure if this is the best way to balance a pack for longevity, or even what a high resistance, low state of health battery does to a pack. Perhaps I should be eliminating those batteries altogether?
Specs:
26x Eaton Powerware 12v 390W VRLA AGM batteries, forming two strings in series of 13 batteries for 24v. (Appx 100ah 12v ea)
I've been using it as is for the last two years. I has been performing well with daily discharges of 500-600ah @24v, it has stayed balanced up until recently. The lower side is dropping off much quicker than upper side. I regularly pull 250amps from it (for electric oven or clothes dryer) and charge around 100amps with solar.
Yesterday I charged both sides up to 14.2v and held them there overnight, then this morning I disassembled and tested each battery on a digital CCA load tester, marking down the cranking amps and internal resistance. I put it in a spreadsheet to try to figure out which batteries I should switch to balance average resistance and CA on pack (so they would discharge and recharge equally). I'm not sure if this is the best way to balance a pack for longevity, or even what a high resistance, low state of health battery does to a pack. Perhaps I should be eliminating those batteries altogether?
Specs:
26x Eaton Powerware 12v 390W VRLA AGM batteries, forming two strings in series of 13 batteries for 24v. (Appx 100ah 12v ea)
Ohms (Left 13 batteries) | CA | Ohms (Right 13 batteries) | CA |
12.4 | 300 | 13.1 | 280 |
6.3 | 585 | 10.2 | 365 |
9.5 | 395 | 6.8 | 550 |
5.5 | 675 | 11.7 | 315 |
12.1 | 305 | 11.1 | 335 |
11.6 | 320 | 6.7 | 560 |
8.2 | 455 | 11.3 | 330 |
8.3 | 450 | 5.8 | 645 |
7 | 530 | 4.9 | 750 |
7.4 | 505 | 11 | 340 |
10.9 | 340 | 11.1 | 335 |
13.7 | 270 | 6.7 | 555 |
5.1 | 735 | 7.6 | 490 |
average Ohms 9.1 | 5865 | average Ohms 9.1 | 5850 |
TOTAL CA | TOTAL CA | ||
Lower 12v | Upper 12v |