Sealed Batteries

Thread Starter

R!f@@

Joined Apr 2, 2009
9,728
I got these two.



Both is around 8V.
Takes very low charging current and handles light loads.

I like to know whether I can revive these ?
 

mcgyvr

Joined Oct 15, 2009
5,394
In general its not worth your time to try to revive a SLA battery. Once sulfation has set it you are better off just buying a new one.

Sometimes you can just fully charge it then let it sit for a day or two then charge again and again.. Other times an over-voltage charge might work.. But in general it never really works well with SLA batteries.
 

jimkeith

Joined Oct 26, 2011
540
What I have observed with dead gel cells is that if you apply a high voltage (e.g. 25V) and monitor the current, you can predict what will happen. If the current decreases, the battery is likely history--if the current gradually increases (possibly unstable at times), it will continue to increase and will eventually start taking a reasonable charge, at which time you start reducing the voltage.
 

jimkeith

Joined Oct 26, 2011
540
Won't applying high voltage is dangerous.
Limit the current to perhaps 0.5A via series resistor or current limited PS and there is little danger--of course wear your safety glasses if you have your face in it.

The only time I had a lead-acid battery blow up was when my engine timing light clip came off the spark plug and came to rest on the case of the battery. Fortunately, the blast (pop) soaked my sweat shirt with acid rather than my face--later the sweat shirt looked like it had been hit with a shotgun blast. One of my many survivor incidents...
 
Last edited:

t06afre

Joined May 11, 2009
5,934
What I have observed with dead gel cells is that if you apply a high voltage (e.g. 25V) and monitor the current, you can predict what will happen. If the current decreases, the battery is likely history--if the current gradually increases (possibly unstable at times), it will continue to increase and will eventually start taking a reasonable charge, at which time you start reducing the voltage.
An interesting tip. Lead acid batteries may in some deap discharge cases get something that is it is referred to as "cell reversal. it is possible for one or more cells to reverse polarity. One cure for this as I have heard is charging the battery with overvoltage. But I do not know if this is true or not. Doing some quick Google serch. I found out that the most common tip to fix "cell reversal". Is to compleatly discharge the battery and then Then recharge at VERY LOW charge rates. But I have no personal experince with this in any way.
 

Thread Starter

R!f@@

Joined Apr 2, 2009
9,728
I have problem with building the de-sulphator. I got no way of measuring the inductance of the inductors I can get.
 

jimkeith

Joined Oct 26, 2011
540
An interesting tip. Lead acid batteries may in some deap discharge cases get something that is it is referred to as "cell reversal. it is possible for one or more cells to reverse polarity. One cure for this as I have heard is charging the battery with overvoltage. But I do not know if this is true or not. Doing some quick Google serch. I found out that the most common tip to fix "cell reversal". Is to compleatly discharge the battery and then Then recharge at VERY LOW charge rates. But I have no personal experince with this in any way.
I know this happens with NiCads--causes cells to short--may be cleared via momentary high current charge.

Never heard about lead-acid doing this, but since multiple cells are connected in series and do not all discharge to zero at the same time, it has to happen.

Completely discharging the battery guarantees that more cells will be reversed--probably not a good idea.
 

hwy101

Joined May 23, 2009
91
On my other forum with EBikes we have had some success with those batteries if they are less than 5 - 6 years old, the cells dry out.
Pry off the top plastic cover and you will see the rubber caps for each cell.
Add a little distilled water to each cell (NOT TAP WATER) just enough to reach the top of the plates, don't over fill.
Then recharge the battery again, this should be done outside, not indoors.
 
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