12v AGM Battery Self Discharging.

[tankace]

12 volt 900 cool cranking amp AGM battery self discharging losing 0.03V everyday even when disconnected (so completely discharge in about 3 week max).

Load test seem to be ok. 900 amps when full charge 800 even a 11.95v.
Individual cells seem to be ok at 2.05-2.10V
Cells does appear to be dry even for a AGM battery (fiber mats appears to be dry on top get no moister if swabbed).

When first open the lids does show amounts of condensation from all cells.

Already add 3cc water to each cell. Which was complete absolved by the mat (did not see any difference)
So the questions is should I add distill water until fiber mats appears to be wet? And can this possible solve my self discharging problem? Or better to leave this thing alone.

 

[snoobler]

Welcome to the forum.

The most important question....

Over how many days did you check it?

.03V/day for the first several days isn't a concern at all. It should plateau around 12.6-12.7.

You've already broken the seal, so it's probably past the point of no return.

AGM is electrolyte starved, so you shouldn't generally see moisture.

Electrolyte loss manifests more as capacity loss and internal resistance increases.

Adding water dilutes the SG and gives more raw material for venting potential.

 

[Supervstech]

To expand on the above post,
When fully charged, agm will be around 14V
It will drop voltage rapidly and settle around 12.8V normally.
From there it shouldn’t drop more than .1 v a week...

 

[Topper]

I played with adding water to AGM's. I saw an immediate boost of capacity and charge acceptance for a week, followed by a very rapid decline within 3-4 days.
My end result was a complete waste of my time and a much faster death to my AGM's.

 

[Substrate]

Oh man, we see this often. Popping open AGM's and adding water. Of course it dies pretty quickly, usually after bubbling out some electrolyte first.

But here's a fun fact if you still want to *goof* around with it. When you added water, you more or less turned it into a flooded lead acid frankenstein. Normal agm charge routines as you've seen totally ruin it quick.

For play type purposes, charge at a float voltage like 13.4 volts or thereabout from here on in. AND, you can no longer assume the 0,2 ti 0,5C current charge rate. It must be treated like a flooded now, using no more than about 0.15C to charge.

Keeps your desk cleaner.

But once you open an agm *with or without adding water* you have destroyed it for the most part. I wouldn't even call it "second life", but just something fun to learn on before you recycle it.

 

[tankace]

Welcome to the forum.

The most important question....

Over how many days did you check it?

.03V/day for the first several days isn't a concern at all. It should plateau around 12.6-12.7.

You've already broken the seal, so it's probably past the point of no return.

AGM is electrolyte starved, so you shouldn't generally see moisture.

Electrolyte loss manifests more as capacity loss and internal resistance increases.

Adding water dilutes the SG and gives more raw material for venting potential.

Everything I am describing is before I open the battery.

Over how many days did I Check? At least 1 week (twice a day). From Fully charge with a floating battery (14.4v charging to 13.2v floating).
Day zero 13.2v, day 1 drops to 12.6 still, day 2 12.5 still normal up to here, day 3 12.45, day 4 12.4, day 5 12.37, day 6 12.34, day 7 12.31 from there pretty consistence loosing .03v each day to 12v. (done this multiple times)

And the history on this battery is that this is a used battery from a used battery shop. And I am pretty sure that they rapid charged this battery before they sold it to me. Battery was warm to the touch when I got it. Also possible battery been open before. Sticker all gone and the caps are screw on type.

The other observation was that the battery seem not to be getting fully charged and it was getting hot while charging. The reason I say that is on a normal battery with my floating charging. The voltage of the battery would increase while charging to 14.4 volts then goes into the floating mode at 13.3 and does not get warm to the touch. This battery's voltage does not get higher higher then 13.7-13.9 volts when charging and just get hotter (warm to the touch 85-90 deg F).

The questions remains does anyone know what is going one. And what is the best thing I can do at this point?

 

[tankace]

I played with adding water to AGM's. I saw an immediate boost of capacity and charge acceptance for a week, followed by a very rapid decline within 3-4 days.
My end result was a complete waste of my time and a much faster death to my AGM's.

did you remember how much water you added to each cell??? Did you add enough water to cover the plates as if it was a flooded??

 

[snoobler]

You have a dead battery.

 

[Substrate]

@tankace - thank you for being honest about it being a used battery. Seriously. We can move forward with a solution.

What you are describing is very typical of an agm that has been gassed-out due to improper charging, typically overcharge.

It is a sign of damage that can come from buckled / shorted plates. One common way to damage an agm is to let it discharge and sit around getting hard sulfated. Hard sulfation physically expands and can break plates and grids. To add insult to injury, trying to charge it back up, by say normal means, damages it further resulting in the symptoms you are seeing now.

Solution: If you are going to experiment with used batteries where the history of charge and care is unknown, spend a few bucks on a VERY smart charger that will tell you right away that you've got major issues, and not just bake things until a timeout occurs.

Marketing hype aside, save your time and frustration with a Tecmate-Optimate charger. It has built-in diagnostics, with an internal charge profile in it's rom that can detect problems and either decide to continue, or better yet, stop with a fail after trying it's best, and inform you that you are wasting time trying to go further.

Something like a Tecmate-Optimate 6 or 7 would do fine. You can *trust* it when it indicates a fail, unlike other chargers that may bake the battery until their safety timeout kicks in.

All my attempts to outsmart it with other charging techniques failed, wasting my time.

If one is going to play with used batteries, then a Tecmate-Optimate charger is your best *diagnostic* instrument for the consumer - the most important being that if it recovers - fine, but in most cases, proof that what you are trying to charge is simply too far gone to waste any time playing around with any further.

Depending on circumstances of where you bought it, a picture of the charger in the failed condition with an Optimate *may* help in getting a replacement. Maybe.

 

[tankace]

@tankace - thank you for being honest about it being a used battery. Seriously. We can move forward with a solution.

What you are describing is very typical of an agm that has been gassed-out due to improper charging, typically overcharge.

It is a sign of damage that can come from buckled / shorted plates. One common way to damage an agm is to let it discharge and sit around getting hard sulfated. Hard sulfation physically expands and can break plates and grids. To add insult to injury, trying to charge it back up, by say normal means, damages it further resulting in the symptoms you are seeing now.

Solution: If you are going to experiment with used batteries where the history of charge and care is unknown, spend a few bucks on a VERY smart charger that will tell you right away that you've got major issues, and not just bake things until a timeout occurs.

Marketing hype aside, save your time and frustration with a Tecmate-Optimate charger. It has built-in diagnostics, with an internal charge profile in it's rom that can detect problems and either decide to continue, or better yet, stop with a fail after trying it's best, and inform you that you are wasting time trying to go further.

Something like a Tecmate-Optimate 6 or 7 would do fine. You can *trust* it when it indicates a fail, unlike other chargers that may bake the battery until their safety timeout kicks in.

All my attempts to outsmart it with other charging techniques failed, wasting my time.

If one is going to play with used batteries, then a Tecmate-Optimate charger is your best *diagnostic* instrument for the consumer - the most important being that if it recovers - fine, but in most cases, proof that what you are trying to charge is simply too far gone to waste any time playing around with any further.

Depending on circumstances of where you bought it, a picture of the charger in the failed condition with an Optimate *may* help in getting a replacement. Maybe.

can't return it! 90 days warrentee passed. To their credit they did exchanged one already before the 90 was over (same problem but worst).

I look into getting the Tecmate (but pro bally don't want to spend the money for now).

Let me know if there are any other suggestions. (anyone).

Right now my plan is the let this one sit (since I just open ad added water) and let the voltage drop by itself to about 12.0 (currently at 12.33). And see how it charges up.

I will let you guy know how this one turn out.