AGM Battery electrolyte top off

[KrisZ]

In short, it can be done.

The Costco Interstate AGM battery in my Grand Caravan was getting slow when cranking during our below freezing weather recently. Earlier this year I notice that the resting voltage hovered around 12.6V. Even if I charged it overnight, it would drop to this voltage pretty quickly.
The date code is 07/22, and outside the costco warranty. The battery was never run low and I would charge it overnight from time to time.

The hardest part was getting the caps off. There are not designed to be taken off without some sort of special tool.
My special tool was a chisel hammered into the cap. One had top threads stripped from the factory and didn't want to come out, but I got it out in the end.

I don't have the any pics of the plates, but they were all dry. It took about 30mls of distilled water into each to make them look wet again.
Charged it overnight at 2 amps, then discharged it to about 12.2V with some halogen lamps and charged it again at 2amps.

Now it's holding 12.8V and I hope I can get few more years out of it. Texas heat is not really kind to these "sealed" batteries as the electrolyte evaporates quite easy out of them. Now that the caps are easy to remove, I will probably top them off every year.

 

[samven]

I dont know why they keep calling these sealed lead acid batteries AGM but yours is not the first I have heard of or seen. A true AGM has no water in it, it is a paste between the plates and it cannot be filled or repaired. The sealed lead acid uses a different plate material and the venting is suppose to reduce water loss but it does not prevent it leading to early death if you dont do what you did and pry the caps off to water it.

 

[Stumpalump]

Those batteries are sealed but can vent and dry out. Good for you for fixing it! I have drilled holes and filled them with a syringe. Seal it with RTV. You may like this trick as well… Batteries often die because sulfate builds up on the plates. That sulfate will short out between pos and neg of battery and show up as a dead cell. It will read in the 10 V range. A battery has a very strong case so you take it and slam it down squarely on the bottom on concrete. You literally have to just pound it on the floor as hard as you dare to not break it. Slam it about 10 times and it breaks the sulfate loose and that crap falls to the bottom of the battery and it is not shorted anymore. Charge up and you just gave a new life to a shorted out battery with a dead cell. It works good on optimum batteries as well. My results have been that I can save about 30% of batteries. Of course at that point you’re only buying time but it will often make a dead cell battery usable for more time. Now I knock any old battery on the floor if I have it out as prevention. It works.

 

[Volvo_Expert_Tech]

Those batteries are sealed but can vent and dry out. Good for you for fixing it! I have drilled holes and filled them with a syringe. Seal it with RTV. You may like this trick as well… Batteries often die because sulfate builds up on the plates. That sulfate will short out between pos and neg of battery and show up as a dead cell. It will read in the 10 V range. A battery has a very strong case so you take it and slam it down squarely on the bottom on concrete. You literally have to just pound it on the floor as hard as you dare to not break it. Slam it about 10 times and it breaks the sulfate loose and that crap falls to the bottom of the battery and it is not shorted anymore. Charge up and you just gave a new life to a shorted out battery with a dead cell. It works good on optimum batteries as well. My results have been that I can save about 30% of batteries. Of course at that point you’re only buying time but it will often make a dead cell battery usable for more time. Now I knock any old battery on the floor if I have it out as prevention. It works.

This comment literally goes against all automotive standards and training. A dropped lead acid battery is a soon to be bad battery. It risks damaging the lead plates and connections. At the dealership, if we dropped a LA battery, we swapped it out with another and sent it back to interstate.

The true way to knock the build up off the plates is a very slow and long trickle charge that will cause the plates to vibrate and knock the crap off.

 

[KrisZ]

I dont know why they keep calling these sealed lead acid batteries AGM but yours is not the first I have heard of or seen. A true AGM has no water in it, it is a paste between the plates and it cannot be filled or repaired. The sealed lead acid uses a different plate material and the venting is suppose to reduce water loss but it does not prevent it leading to early death if you dont do what you did and pry the caps off to water it.

It is still an absorbed glass mat though. Not a flooded lead cell. I guess that's how they make them cheaper?

 

[KrisZ]

Those batteries are sealed but can vent and dry out. Good for you for fixing it! I have drilled holes and filled them with a syringe. Seal it with RTV. You may like this trick as well… Batteries often die because sulfate builds up on the plates. That sulfate will short out between pos and neg of battery and show up as a dead cell. It will read in the 10 V range. A battery has a very strong case so you take it and slam it down squarely on the bottom on concrete. You literally have to just pound it on the floor as hard as you dare to not break it. Slam it about 10 times and it breaks the sulfate loose and that crap falls to the bottom of the battery and it is not shorted anymore. Charge up and you just gave a new life to a shorted out battery with a dead cell. It works good on optimum batteries as well. My results have been that I can save about 30% of batteries. Of course at that point you’re only buying time but it will often make a dead cell battery usable for more time. Now I knock any old battery on the floor if I have it out as prevention. It works.

I heard of the drop trick but that's sounds risky. A much better way to de sulfate is to run high current though it, like 50-100 amps, but you need a manual charger for it and you need to monitor the battery temps and do it in short bursts.

No matter how you slice it, a battery can often be saved, but it needs lots of time and babysitting.

 

[RaymondP]

My charger has a reconditioning (desulphating?) setting. Haven't tried it. Has anyone seen good/worthwhile results with this process. Battery is a BMW (Varta) AGM, H8/49, now ten years old. Probably not worth messing around? Replace?

On a previous Merc started to have strange issues that were resolved after battery was replaced. No issues so far on the BMW.

 

[f355spider]

My charger has a reconditioning (desulphating?) setting. Haven't tried it. Has anyone seen good/worthwhile results with this process. Battery is a BMW (Varta) AGM, H8/49, now ten years old. Probably not worth messing around? Replace?

On a previous Merc started to have strange issues that were resolved after battery was replaced. No issues so far on the BMW.

Yes, it can work. I own several Battery Minder brand chargers and they desufate continously. Since it is continous, it is also slow. Can take several weeks to complete. In one case I saw improvement over about 7 or 8 weeks, then stabilized.

I have an AC Delco AGM H8/Group49 that is 7 years old and works great. I put it on the Battery Minder overnight a couple times a week.

 

[Donald]

I think the BatteryMinder tech support said to leave it connected doing it's continuous desulfating and check it with a battery tester each week. When there is no change from the previous week it's as good as it will get.

For a battery in a regularly driven car or truck Ivan not sure how that works. For a boat battery with an off season yes it might work.

 

[Sequoiasoon]

My CTEK 7002 has a "recondition" mode that is supposed to de-sulphate it, it works overnight basically. I bought the charger based on videos of Optima using it to bring some spiral cells back to life and battery videos by Kent Bergsma (mercedessource on Youtube). I also bought and use the Solar BA9 tester after that.

 

[Snagglefoot]

It’s all fun and games until someone loses an eye.

 

[dogememe]

Not a good idea IMO and it will not work very well for long. Just replace it.