Battery restoration myths and facts

CALLD

Ok, I decided to see for myself what's possible and what isn't. So many people claim to be able to "restore" batteries to original condition by adding water, desulfating etc.

I retrieved a 12v8ah gel battery from an ancient electric fence energizer and checked the voltage - 0.00volts was the reading on the digital multimeter. Awesome!

Promptly hooked it up to a charger and waited an hour, removed the charger and checked the voltage - 3.74volts was the reading. Battery was unable to deliver any meaningful current though. Left it on charge for 24 hours. Next day the voltage was reading 6.82volts. Still not able to deliver any meaningful current. Dead you say? Not quite...

Removed the top seal and cell caps, added a little water to each cell until the fibreglass spongy seperators looked wet enough, put it back together. Hooked it up to the load terminals on my solar charge controller (which was at 26.8v at 8:30am) so I could see if it was accepting any charge current. Load reading was 0.0amps at first. After half an hour it had changed to 0.1amps. I was watching it like a hawk just in case the current started to climb rapidly and forced me to disconnect it and move it to the 12v charger. After another 20mins the current climbed to 0.2amps. Next 20mins it's at 0.3amps. 2 hours into the 26.8v (and climbing) charger the current reading is 1.2amps. By 11:00am (2:30hrs of charging) the current is at 2.6amps and rising rapidly. Moved it over to the 12v charger and left it to charge for the rest of the day. The battery was getting nice and warm to the touch (a good indication of charge acceptance and breaking down of sulfate on the plates). Removed the battery from the charger at 21:30 and let it rest and cool overnight.

The next morning I took a voltage reading - 12.48volts. A fully charged VRLA/gel battery should have had a voltage of 13.0volts or more after a nights rest from charging so either it wasn't fully charged OR full capacity wasn't restored. I would be inclined to believe the latter. It was however able to power a 12v50w halogen lamp for 35mins before the light faded to an orangey glow. A new battery of the same type would have been able to do so for over an hour at least.

So there you go - some restoration is possible but full restoration? I don't think so...

westbranch

CALLD wrote: »

a 12v8ah gel battery

Are you sure it is not an AGM ?

CALLD wrote: »

the fibreglass spongy seperators looked wet enough,

that is what AGM s look like inside...

BB.

Also cycle the battery for a few weeks and see what happens... Many times, I have seen automotive batteries (more than 1-2 years old) die/get killed, recharged, and then used normally for the next few weeks, only to die again without warning (days to a couple weeks).

-Bill

CALLD

westbranch wrote: »

Are you sure it is not an AGM ?

that is what AGM s look like inside...

It says "GEL battery" on the battery

CALLD

BB. wrote: »

Also cycle the battery for a few weeks and see what happens... Many times, I have seen automotive batteries (more than 1-2 years old) die/get killed, recharged, and then used normally for the next few weeks, only to die again without warning (days to a couple weeks).

-Bill

Will do:)

I've also tried the same thing with a "dead" car battery and noticed similar results.

They do accept some charge, but never attain the same open circuit voltage as a new equivalent, 12.4 to 12.5 is what I'm seeing irrespective of how long I leave them on charge for. Their current delivering capacity is also much less. What seems to be possible is that you can recover a portion of the battery's original capacity. Sulfation is probably the cause of lost capacity. The result is a lower SG resulting in lower voltage, higher internal resistance and less load handling capability. Try what you like you cannot get the lead sulphate on the plates to recombine into acid. This is fine if you just want a battery to mess about with, but no good to rely upon. Of course, the battery could fail without warning should the plates short out or disintegrate for some reason...

gww1

I guess if you have lots of energy and are interested in this type of stuff, reading this could keep you busy for a while.

http://www.thebackshed.com/forum/forum_posts.asp?TID=2979


gww

CALLD

gww1 wrote: »

I guess if you have lots of energy and are interested in this type of stuff, reading this could keep you busy for a while.

http://www.thebackshed.com/forum/forum_posts.asp?TID=2979


gww

Thanks gww, interesting read of the first few pages. But I now suppose results will differ depending on the battery. It's difficult to know what the condition of the plates are without taking the whole battery apart which doesn't seem worthwhile to me, especially since I'm working with AGM's. I'm busy cycling my specimen now to see if that makes a difference. At least so far it doesn't seem to have a dead cell, they all just seem heavily sulphated. These guys like to use their "desulphators", which I'm yet to be convinced make any difference to normal charging. I for one have notice that merely leaving batteries on extended float charge (weeks) can remove stubborn sulphate resulting in higher overall SG readings.

gww1

I think at about page 34 of the post I linked, the guy was getting ready to do a load test of what he worked on. They are big on desulphators and have a couple of diy ones listed. I also didn't think it worth the effort to make or buy one. I did find their expermenting a bit interesting and they seem to make an effort to be helpful to new guys but from their perspective that they really believe in the desulphators. Good luck
gww

CALLD

gww1 wrote: »

I think at about page 34 of the post I linked, the guy was getting ready to do a load test of what he worked on. They are big on desulphators and have a couple of diy ones listed. I also didn't think it worth the effort to make or buy one. I did find their expermenting a bit interesting and they seem to make an effort to be helpful to new guys but from their perspective that they really believe in the desulphators. Good luck
gww

Yeah these guys really do get into it with a lot of passion - it's a bit above my knowledge to be honest.

However I do like to know what's possible and what's just hype & hope. The thing about de-sulphators is that they somehow can't find their way into the textbooks despite having been around for ages. Would make me skeptical but not completely unconvinced - would love it if someone gave me one (for free of course) so I could try it for myself. The same goes for lead crystal batteries - a type of gel/agm/vrla sealed battery that claims to have a cycle life comparable with the best deep cycle fla batteries out there but with the ability to cycle down to 0% Soc hundreds of times without any loss of capacity. On top of this they have the same low internal resistance as AGM batteries so they have the same very high charge/discharge efficiency and high-rate abilities. They are expensive though but not too prohibitive. Also unable to find their way into the text books for some reason...

CALLD

As for my little 12v8ah specimen, it's been cycled 4 times down to 10.5v with a 50w load and a 26w load (incandescent lightbulbs). The 50w bulb takes 40mins to get it down to 10.5v and the 26w bulb takes 85mins to do the same. This suggests a usable capacity of about 3 to 4 Ah or roughly half of it's original rated capacity. I've got it on an extended absorb charge at 14.4v right now and am going to see what 24hrs at this voltage can achieve - perhaps some of the hardened sulphate will manage to recombine. Will report back soon.

westbranch

CALLD wrote: »

The thing about de-sulphators is that they somehow can't find their way into the textbooks despite having been around for ages.

Not to start a lot of debate, but this begs the question: Why does the Canadian military use them, on vehicles that have long non-use periods, if they don't work to some degree?