2V FLA cell failure

OzSolar

Started out w/nothing & still got most of it left
Joined
Jan 5, 2021
Messages
618
Location
Southwest MO
Did an equalize charge on my 48v Surrette pack this week. Found one cell with a SG of barely above 1.xx and about .3 volts lower than the others. After several more tries it still didn't budge pulled it out until I can try to do an EDTA treatment..... or maybe it's time to look at server rack batteries.

22 years old so the rest aren't far behind.

Wired around it and adjusted the voltage settings to reflect the missing 2V cell. 30 minutes later I was back in business.

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OzSolar

Started out w/nothing & still got most of it left
Joined
Jan 5, 2021
Messages
618
Location
Southwest MO
EDTA treatment? 22 years, that is remarkable!
Maybe EDTA but is it really worth the hassle. Based on NO personal experience my best guess is the I might end up with a battery that is 75% of it's original capacity when and might just be adding a few years. Maybe I'll do it to 6 of them just as an experiment but I've got plenty other things to do. Do you know much about it?

I think my time is better spend building a 16S1P ~300 AH LiFeP04 pack.

They've lived a pretty sheltered life. I was holding them for a couple who was building an off grid home but they split up half way through. One of them spent years trying to scrounge together the money to finish the house but they never did so I just ended up with them.

I kept them float charged for about 4 years then I realized it would just be best to integrate them into my grid tied battery back up system. I've monitored SG very closely and equalized as needed. They probably had less than 50 serious cycles over the years and now it takes 15 amps just keep them at float voltage. That's about 1kW constantly on the AC side so I'm not doing that anymore.
 

saggys

New Member
Joined
Aug 14, 2021
Messages
29
I am unfamiliar with EDTA treatment, is it an acronym or a procedure?
 

OzSolar

Started out w/nothing & still got most of it left
Joined
Jan 5, 2021
Messages
618
Location
Southwest MO
I am unfamiliar with EDTA treatment, is it an acronym or a procedure?
It's a "rebuilding" procedure with a type of salt called EDTA. I've heard Epsom salt getting mentioned as well.

Some people say you can add it directly to the battery.

Others say it is much more effective to remove the old electrolyte, fill up the cell with water, add a small amount EDTA and let that soak over night which will remove most of the sulfate. Dump that out then add fresh battery acid to the cells. Ta-da you've got a brand new battery.... probably not though. That seems like the way I would go but what a dangerous project. I've got 24 cells that are 2' tall.

And of course you've got some nasty stuff on your hands which I assume your local battery place can take?? Sure as heck don't want to pour that down the drain.
 
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