Recovering a dead battery (SLA, voltage was not maintained)

Thread Starter

Tonyr1084

Joined Sep 24, 2015
7,777
I have a 6 volt 1.2 AH SLA battery. The voltage was allowed to drop and now won't take a charge. It is currently measuring 1.8 volts with no load. Is there a way to recover the battery? It's only a year and a half old and was only a backup battery for a home security system. Just wondering if it's worth charging or if it should go in the recycle bin.
 

ScottWang

Joined Aug 23, 2012
7,396
Try to using a low current as 10~20 mA to charge it, if it can be charged then it will be spend more than 50 hours to charge it.
 

MrAl

Joined Jun 17, 2014
11,263
Hello,

I have three such batteries now, one is only about 2 years old.

I have read now that the longer it goes without being charged the less likely it is to recover from sulfation using electronic methods and that is because the material that accumulates on the plates is non conductive and gets harder with age. The harder the material, the harder it is to get off the plates. The only way to proceed after that is with a chemical method that requires open cells to deal with the insertion of chemicals to get rid of the hard material. Obviously we cant do that with a gel cell.
Unfortunately, i've also read that after a successful electronic desulfation we could end up with what they call "soft shorts" that partially short out the plates making the self discharge get worse.

The main problem is the stuff that gets on the plates, and how to get it off the plates. If you cant get it off the plates then there's no way to charge it properly again. Ideally if the battery can be taken apart and cleaned, it would be restored to nearly full capacity. But that's not a task i want to have to do and not sure how this would work with a gel cell. Maybe someone wants to look into this though. if they have a gel cell that is completely discharged to 0.00v, it might be interesting. If it is not discharged completely though i would not do it because something might short out. The plates would have to be cleaned and i am not even sure that is possible as i have never taken one apart. IF they are too close together it may be too hard to get in between them to clean them properly.

One battery i have that is only about 2 years old, it reads close to 0 volts, then when i apply 14v it jumps right up to 14v and draws no current, then when i disconnect the supply it jumps right back down to 0 volts. It obviously has material on the plates that stops it from conducting current, and so it wont charge now.
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
7,777
It's just a small 1.2 amp 6 volt battery. I don't directly have a use for it, which is why it sat unused all this time. Oh well. I'm not about to open it up and play with acids or other chemical means to rejuvenate a battery that probably costs $7 to $10. Was wondering if there was a way.

Many years ago, working for an emergency lighting company, they scrapped some batteries. Not sure exactly what they were, for some reason Mercury cells comes to mind. Each battery was a little larger than a D cell battery and was capable of massive amounts of current when it was good. I made a crude charger and (back when I didn't know much about chargers or batteries) hooked it up for the night. The next day when I checked the batteries I discovered I reverse charged them. First I was happy they didn't explode. Second I was astonished to discover that they TOOK the reverse charge. Keep in mind this was some 40 years ago, so exact details have been lost to vagary of not knowing what I was doing, what I did or why it appeared to behave that way. So I came here to ask. I thought someone might suggest reverse charging the battery for a period of time, then to charge it properly. I don't know. Maybe that would work. But maybe someone has experience with a reverse charged SLA battery and would most vehemently advise against doing that. Unless I wanted to put the battery out in the yard and charge it, so that if it exploded no property or life would be harmed. Like my ditty below says: "A little bit of knowledge is a dangerous thing in the hands of the fool who doesn't know what he doesn't know." I'm a FIRM BELIEVER that if you KNOW you don't know something - DON'T EXPERIMENT. ASK! Learn. So I ask.
 

bwilliams60

Joined Nov 18, 2012
1,442
Reverse charging is definitely not a good idea and will not do anything to remove sulphation from the plates. One thing you need to keep in mind is that sulphation is a crystalline form that attaches itself to the plate. When you charge the battery or blast charge which seems to be popular, you remove or break down the crystal but you also break down the lead composition and a portion of it will break away from the plates and weaken its capacity. Your battery in the short answer....is toast. Time for a new one.
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
7,777
Time for a new one.
Yeah. I'm sure it is. Was just wondering if there was a stupidly easy trick. Kind of knew there wasn't one from the get-go. I now have a couple old batteries to recycle. Replace? Nah. Don't need one just now. If or when I need one I'll go get one.

Thanks all for the comments.
 
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