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Unicorn Driver · 04-14-2022, 05:32 AM

Hi,

I have 4 lifeline AGM batteries that I am not using as moved to Lithium but would like to try to rescue them.

I have them hooked up to a 10amp Noco charger and no luck.

Is there any business that can get them back? They are only 4 years old but Lifeline will not cover because they got below 8v. I think they may have froze.

Thanks,

Stephen

Alpine36 · 04-14-2022, 09:08 AM

I've had good luck bringing dead AGMs back by paralleling a known good decently charged 12v lead acid battery together with the dead AGM with jumper cables. Hook a conventional (non smart) battery charger to both and charge at about 10a for 24 hours. Disconnect the lead acid battery and charge the AGM with the NOCO until fully charged. Repeat with all your AGM batteries, one at a time. I've brought back many Optima and Odyssey AGMs this way. It's a slow process but it will work.

Unicorn Driver · 04-14-2022, 06:27 PM

Thanks Alpine for the great info.

Besides these the only other lead acid I have are the batteries in our vehicles.

Would a car battery do?

Alpine36 · 04-14-2022, 09:00 PM

Quote:

Originally Posted by Unicorn Driver

Thanks Alpine for the great info.

Besides these the only other lead acid I have are the batteries in our vehicles.

Would a car battery do?

Yes, anything to "trick" your battery charger. The AGMs take quite awhile to come around. Be patient. I've had AGMs take days to fully charge.

Persistent · 04-15-2022, 10:39 AM

Deep Discharge

There are RV battery chargers that will not charge when the voltage drops below the charger cut off point. Charge battery with an external charger until the voltage is higher than the cut off point. That will then let the RV charger finish charging.

A full clean charge is recommended soon after the deep discharge. That means 14 to 18 hours using a high quality charger like the one you probably have in your RV. Sometimes 24 or more hours is helpful.

I have successfully recharged both GEL cells and AGM batteries from flat out discharge. Both banks continued to work just fine for many years afterwards. There was no obvious loss of capacity in either case.

Sulfated lead acid batteries

Lead acid batteries that have been left discharged have lead sulfate on the plates. Lead sulfate crystalizes slowly. Crystalized lead sulfate is hard to redissolve by charging. Very low charge rates for a long time are needed to redissolve.

Clean charged lead acid batteries that are then discharged need to be fully recharged soon. A few days or a week is probably OK. Leave them on charge longer to help clean crystalized lead sulfate off. It takes a long time to make the crystals, it takes a long time to dissolve them.

If you leave your battery discharged for 3 months, they will likely not be recoverable using normal charging profiles. They may never work the same in any case.

Crystals can fall off the plates. This often happens as deeply discharged flooded cells recharge. The loose material at the bottom of the battery can not usually be recovered.

AGM batteries have less issue with crystals falling off. The mats between the cells tend to hold the crystals in place. They still need a long time to redissolve at very low charging rates (probably milliamps).

There is a process to recover to some degree from batteries left deeply discharge for a long time. It involves limiting the charge current to very low values and applying for a very long time.

Special equipment and special procedures must be followed. I don't know what they are. Some business provide that service. Do you trust them?

Not all batteries behave the same. Different designs have different issues. The manufacture is usually the only good source for data. If Lifeline says 8 volts is too low, that is probably true. But if they did not say why, it may mean something different than we imagine.

I wish you good luck and happy trails ahead!