caveman.b
New Member
I was gifted 4 used 12V 126AH AGM batteries a couple of years ago when a friend upgraded his (new to him) sailboat and they have been sitting in my garage (being charged every once in a while). I am not sure what configuration they were used in before, but I suspect it was 2S2P. Two have a date of 6/2020 and 2 of them have date of 2/2020.
I wired them into a 2S2P configuration (in dated pairs) in my cargo trailer after charging all batteries within .01 V of each other to power a 24V system in a test situation temporarily until I get permanent location for all of the equipment (inverter, solar, shore power, transfer switch, charger all separate). The batteries are all connected direct without bus bar (lead battery for one parallel string directly connected to main pos and the other to neg bus). I don't have any individual monitoring set up on the batteries, currently. After operating (mostly sitting with charger attached - wired to main pos and neg bus) and using some 12v led lights (with 12V converter) infrequently for a couple of months I tested each battery individually. The end battery (ie not connected to the main pos or main neg) on each series string was very low (2.0 V and 3.2 V). The lead battery on each string had voltage of 13.1.
I disconnected them immediately and have since charged them up and let them normalize a few times. The batteries that were lead on each string seem fine (rest at 12.99-13.0 after 24 hr) and the other two that experienced the low voltage normalize at 12.85 V. I have seen different charts say different things for expected voltages but majority say resting 100% for AGM is 12.80 so I am inclined to think that something has changed but they are probably still good.
What might have happened to the batteries to cause the low voltage on the end string battery? Can I still use them without causing issues? If so should I pair the similar resting voltage batteries together in series (instead of date pairs)? If not is there any use for them still? Will they cause problems if I use them all together in the future in a 12V parallel system (upgrading to LiFePO4 soon).
I also have a couple of HA01 battery equalizers I can use but I was skeptical about the instructions for the 2s2p instructions. How do I wire these? Do I truly only need one for the entire setup and wire the white to all four batteries as shown in the pic attached? I did see this thread and it sounds like I should wire like the first image (showing 2 batteries in series) on each series string. https://diysolarforum.com/threads/battery-equalizer-for-2s2p-agm.52992/ - my battery setup looks just like the poster's first diagram.
Thanks in advance for any assistance/advice!
I wired them into a 2S2P configuration (in dated pairs) in my cargo trailer after charging all batteries within .01 V of each other to power a 24V system in a test situation temporarily until I get permanent location for all of the equipment (inverter, solar, shore power, transfer switch, charger all separate). The batteries are all connected direct without bus bar (lead battery for one parallel string directly connected to main pos and the other to neg bus). I don't have any individual monitoring set up on the batteries, currently. After operating (mostly sitting with charger attached - wired to main pos and neg bus) and using some 12v led lights (with 12V converter) infrequently for a couple of months I tested each battery individually. The end battery (ie not connected to the main pos or main neg) on each series string was very low (2.0 V and 3.2 V). The lead battery on each string had voltage of 13.1.
I disconnected them immediately and have since charged them up and let them normalize a few times. The batteries that were lead on each string seem fine (rest at 12.99-13.0 after 24 hr) and the other two that experienced the low voltage normalize at 12.85 V. I have seen different charts say different things for expected voltages but majority say resting 100% for AGM is 12.80 so I am inclined to think that something has changed but they are probably still good.
What might have happened to the batteries to cause the low voltage on the end string battery? Can I still use them without causing issues? If so should I pair the similar resting voltage batteries together in series (instead of date pairs)? If not is there any use for them still? Will they cause problems if I use them all together in the future in a 12V parallel system (upgrading to LiFePO4 soon).
I also have a couple of HA01 battery equalizers I can use but I was skeptical about the instructions for the 2s2p instructions. How do I wire these? Do I truly only need one for the entire setup and wire the white to all four batteries as shown in the pic attached? I did see this thread and it sounds like I should wire like the first image (showing 2 batteries in series) on each series string. https://diysolarforum.com/threads/battery-equalizer-for-2s2p-agm.52992/ - my battery setup looks just like the poster's first diagram.
Thanks in advance for any assistance/advice!
Attachments
Last edited: