How much water should I add to old AGM battery?

[Yet another Yeti]

batteryuniversity odd com could be some website to learn more about all different sorts of accumulators ...

[Mike90250]

He's dead Jim.

[inetdog]

AGM batteries are susceptible to sulfation, just not as readily as FLA. Loss of water (only) from the electrolyte will cause loss of capacity but NOT reduced open circuit voltage after full charge. Your voltages and lack of response to charging are most likely the result of irreversible sulfation, not overboiling.
As such, the door stop idea has merit, but the value will be greater as lead scrap. Any AGM battery over five years old, used or unused, is suspect.
However, I do not know of any AGM (sealed) batteries to which you can add water without drilling or using a hypodermic and then resealing to hold gas pressure.
I may try looking the battery up.
Old FLA, especially ones that have been sitting uncharged are unrecoverable because of sulfation. Door stop recommendation still applies.
IF (and a big if) electrolyte was actually spilled instead of boiled off, adding electrolyte rather than water might get you some very limited use.
If the tops of the plates were uncovered for any length of time, the battery will have lost capacity.

OK, that part number is indeed sealed AGM, so there will be no way to add water, period. That is why AGM batteries should never see an Equalize cycle with a high enough voltage and current to cause venting.

[kingofbanff]

I don't have the answer but I'm sorry your first post resulted in an unhelpful/unfunny answer. Stick around there are lots of good people helping out here and one of them more knowledgeable will help you out.

[Paul Land]

Hey guys,

I have a bunch of old Northstar NSB 170FT batteries that are showing voltage in the 10's and 11's. I just realised maybe I can refill the water to give them a second chance at life.They have been in a pretty hot climate and were worked quite hard so I'm sure they have lost a lot of water.

Question is, how much water do I add? All the way to the top till it starts to overflow?

If you add some seeds with your H2o you will have some pretty door-stops

[davethedrummer]

Hey guys,

I have a bunch of old Northstar NSB 170FT batteries that are showing voltage in the 10's and 11's. I just realised maybe I can refill the water to give them a second chance at life.They have been in a pretty hot climate and were worked quite hard so I'm sure they have lost a lot of water.

Question is, how much water do I add? All the way to the top till it starts to overflow?