Not convinced of a short cell. Bad? Possibly. But the voltage appears to have recovered somewhat. The issue now is that it will fully charge but not deliver a full charge. At present the battery voltage has dropped to 10.19V, and the fan has been running constantly. This WILL eventually drop. And I WILL modify my relay circuit so that it falls out at 6V. But right now I'm busy with something else.

 

The issue now is that it will fully charge but not deliver a full charge.

That's an illusion.
The short in the shorted cell is likely a high enough resistance to make it appear that the battery is fully charged, but as soon as you apply a load, the shorted cell voltage drops to zero.
You are beating a dead horse.

 

You are beating a dead horse.

Maybe so.

 

Maybe so.

It doesn't hurt anything to keep trying the battery restorer. It will keep trying to remove sulfation as long as it doesn't determine that the battery is bad.

I had a battery in an Explorer that only gets started a few times a year. The battery is out of its warranty period and was usually dead. I charged it with the battery restorer and it's holding a charge for longer than a month. I use a charger instead of the alternator to do most of the charging.

The lawn mower battery that I restored is still holding a charge. Before I replaced it, it wouldn't even hold enough charge to start the mower after a week.

 

Well, I'm wondering, and maybe this is naive of me, but, if there's a shorted cell, perhaps I can draw a heavy current through the battery and burn the short out like a fuse. Again, perhaps I'm being naive and engaging in wishful thinking. But I have little to do at present. I DO need to glue down a floor in my shop, but that's for a warmer day than low 40's (F).

The battery reached the 8V range under a load when I shut it off. I now have it on the restorer-charger. One of two things can happen; I can get a useful battery, or not. The charger is still useful for other batteries; and thinking of it, I have a battery up stairs that needs to come down and get charged.

 

I WILL modify my relay circuit so that it falls out at 6V

6V is too low for a regular lead acid battery. Something above 10V would be better.

 

perhaps I can draw a heavy current through the battery and burn the short out like a fuse

You could try momentarily shorting the battery after it is charged.
You'll need a large gauge wire and a big switch.

 

hi T,
When trying the shorting method beware of a possible WELD of the switch contacts, if that happens you will have an exciting few seconds.. wear eye protection.

I have seen this happen.

E

 

Don't use a switch to do the momentary shorting. Just touch the ends of the two wires together momentarily. And if they try to weld, pull harder. But if you keep that touch moving welding will not be likely. And do it where the sparks flying will not cause problems. Outside is better.

 

Dropped voltage down to 8V range when I stopped the drain, then put it back on the charger.

As for shorting, have a look at the picture. I can use a couple 12 gauge wires to probe upwards from the terminals, then using a heavy screw driver I can short the leads briefly. And by briefly I mean as long as it takes to read the word "A". Using a switch is a bad idea. OR maybe I could use a fuse of some high amperage. I don't know how many amps this battery can deliver. All I know it's a 20 amp hour rated battery. For all I know it might deliver 100 amps dead shorted. In which case the 12 gauge wires would act as a pretty sizable fuse.

 

hi Tony,
If you use heavy gauge wire to touch the ends to each other, remember the wire will become to hot to handle, also if they WELD.
E

 

Even a 7 amp-hour battery can deliver 100 amps for almost a minute, sometimes more. One place I worked proved that as part of a product.

 

Given that this battery is out of one of those car jump starters I have to imagine it is probably capable of some pretty strong amperage. But right now I'm busy sealing up the door of my shop because we had rain last night and water got in. The contractor didn't seal up the door jam. I now have some cleanup to do, so I won't be giving the battery much attention until this evening when all of you east coasters and others across the pond are fast asleep. Well, unless some of you are night owl's.

 

After several attempts to get this battery back from the dead, I've finally gotten around to attempting to dead short the battery. Everyone expected a lot of excitement - me included. Sadly, the dead short using a 12 gauge wire did not even remotely get warm. Only one cell would boil where you could hear it boiling. So the hypothesis of shorting the battery to burn out the short within the cell - it's a failed hypothesis. AFTER dead shorting the battery, battery voltage appears to be 12.48 volts. Yet, the battery was capable of delivering nearly no current at all. No, I didn't risk my meter to test it. Just want to report that this battery is going into the recycle bin along with another battery.