AGM battery reads 13.1V no load. But is dead.

[KingCake]

I have an AGM battery that sat for a year.

It reads about 13.1volts open circuit voltage. A 100amp load test drops it to 6 volts.

My smart charger won't try to charge it..it reads the 13 volts and goes into float mode...

Anything I can do to try and 'wake up' the agm? Or will I need a manual charger?

 

[spackard]

I assume you are out of the warranty period on it?

Hang a sealed-beam headlight on it overnight to really kill it, then try charging it.

 

[KingCake]

Originally Posted By: spackard
I assume you are out of the warranty period on it?

Hang a sealed-beam headlight on it overnight to really kill it, then try charging it.


It won't even light off my test light. But jumps right back to 13V when disconnected.

 

[Lasthope05]

Run a second good battery in parallel to trick the charger.

 

[EricF]

You need a charger that can push out more than a regular 2/6/10 amp. the battery is so thirsty for electricity, it's drawing more than your 2/6/10amp charger can put out. so the charger circuit breaker breaks, cools down, reconnects and the battery sucks down as much juice as it can till the breaker pops again. it could take days for that process to occur and reoccur until the battery get enough juice to not want to take more than the max amps allowed by the charger.
I know you're not supposed to charge an AGM with more than a trickle, but you need to get it woken up and put some high amp juice into it, and let it start to wake up.

However, sitting for a year, the battery has developeed sulfation. there's a strong chance it won't accept a charge because of this. But a high amp charger, like 30+ amps might (SLIM MIGHT) break the sulfation up and allow the cells to reabsorb juice.

 

[Rand]

I'd try jumping it from another battery for 1min or so then putting on the charger immediately.

 

[KingCake]

Good advice, everyone. I was thinking about hooking it to a good battery to see if it would take charge from it.

Should I hook a light in series to limit the current? The bad battery might have super low internal resistance.

 

[DuckRyder]

 

[JetStar]

You seem to have high internal resistance, due to a broken, cracked, degraded bus bar inside the battery, or it is sulfated. You could try a charger with a sulfation mode to see if that will recover it.

 

[The_Eric]

Originally Posted By: DuckRyder



I think this battery is toast and connecting another battery in series won't help- the giveaway to me is that it reads plenty of voltage while open circuit, but as soon as any load is applied, even a test light, it goes completely away.

I think it's time to stick a fork in it and call it done.

 

[SHOZ]

I would discharge it to 0vs. Then connect the charger backwards and drive it into reverse voltage. Say 5vs. Then a long slow recharge.

 

[Yup]

Seems as if others have covered it in previous posts...but some of those batteries need a special charger. Many newer chargers cover it but my dad had an older one and buying a new one fixed his "bad battery" problem he thought he was having.

 

[KingCake]

Well I forgot to take the float charger off of it. It stayed on there for about 24 hours.

I decided to try charging it again and now it's taking an 8-amp charge no problem!

Not sure if that was the best thing to do or not but it's charging again.

 

[Jarlaxle]

Originally Posted By: The_Eric
Originally Posted By: DuckRyder



I think this battery is toast and connecting another battery in series won't help- the giveaway to me is that it reads plenty of voltage while open circuit, but as soon as any load is applied, even a test light, it goes completely away.

I think it's time to stick a fork in it and call it done.


If so, it seems to me that he has nothing to lose by trying to save what is probably an expensive battery!

 

[kc8adu]

if at 13.1 open then its full.
it may be dry.see if you can get to the valve caps.under a strip usually.add a small amount of distilled water to each cell.
start with like 2cc per.does the load test improve?maybe add 1cc more per cell.if it improves again you might add another.
if no improvement put the valve caps and strip back.try in the bike or whatever it goes to.how big is this battery?

 

[MinamiKotaro]

Originally Posted By: kc8adu
if at 13.1 open then its full.
it may be dry.see if you can get to the valve caps.under a strip usually.add a small amount of distilled water to each cell.
start with like 2cc per.does the load test improve?maybe add 1cc more per cell.if it improves again you might add another.
if no improvement put the valve caps and strip back.try in the bike or whatever it goes to.how big is this battery?


It's an AGM. Totally sealed, and you sure wouldn't want to put water in it!

 

[kc8adu]

if it were totally sealed it would explode.
we remove the strip that retains the valve caps and add small amounts of distilled water.
i use a impedance tester so i can see in real time if its helping.
wont help if the plates are crumbling but if it was dried out from overcharging water helps.
Originally Posted By: MinamiKotaro
Originally Posted By: kc8adu
if at 13.1 open then its full.
it may be dry.see if you can get to the valve caps.under a strip usually.add a small amount of distilled water to each cell.
start with like 2cc per.does the load test improve?maybe add 1cc more per cell.if it improves again you might add another.
if no improvement put the valve caps and strip back.try in the bike or whatever it goes to.how big is this battery?


It's an AGM. Totally sealed, and you sure wouldn't want to put water in it!

 

[SHOZ]

Many AGMs are sealed but have a 10 psi vent.