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Author Topic: Batteries and desulfators - I needs ta know!!  (Read 4034 times)
boogiethecat
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« Reply #30 on: January 06, 2012, 09:56:15 AM »

A DC welder is basically a constant current power supply, so it'd be used the same as the small lab supply, turn it on for 12-24 hours and constantly overcharge the battery. The trick with a welder is that you'd have to be able to turn it down to 5-6 amps.  Many of them can't go that low even on their lowest settings...

And Chaz... yes, that's it! Outside, fireproof (and acid proof) area, well ventilated and NO sparks!!! (I think my adventure was caused by a rat moving a wire that had an alligator clip, causing a spark that way)
You just keep on watering it and charging it, and looking at the specific gravity of the electrolyte.  Eventually it will come up to a normal range for fully charged... that's when you're done... It might take days, and it might not ever happen. But if the battery doesn't have shorted cells, it will work most of the time.
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1962 Crown
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« Reply #31 on: January 06, 2012, 02:14:01 PM »

  So your putting a much higher voltage into the battery at low amperage?

  I have two Trojans that suddenly died about a year ago, and while they are 7 years old and likely done, I would like to experiment with them a bit.

  Back when I was 20 I scrounged a whole bunch of jusn or dead batteries and tried everything I could read about to bring them back to life. Tried flushing them, putting in new acid, over charging, reverse polarity charging, most never came back enough to make it worthwhile and all I really accomplished was running the electric bill up. I never heard of this de-sulfation thing before other than just using a long slow charge.
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Jeremy
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« Reply #32 on: January 06, 2012, 03:15:18 PM »

You probably need to read this thread through from the beginning otherwise you risk doing something dangerous in your 'experimentation'. Boogie gave a good description of the constant-current desulphation process on the first page.

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In recent replies a few people have mentioned bad cells and shorted-out cells; I'd like to understand exactly what is being talked about here. I can imagine scenarios where the plates in one cell could become shorted-out, for example if a broken-off bit of lead got stuck between them or perhaps excessive current draw had heated the plates until they distorted and touched each other.

Is this the kind of shorting-out people mean? And if it is, how can you tell that it has happened? I'm not sure a hydrometer would tell you that, and you can't test the individual electrical output of a lead acid battery in the way that you can with a Nicad pack for instance.


Jeremy
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« Reply #33 on: January 06, 2012, 05:38:10 PM »

Jeremy,

This is just my understanding which is made up of some fact mixed with rumors.  There can be several reasons a cell shorts out.  One way that I have read about involves debris being accumulating between plates for different reasons and causing a short.  In this particular type of short, some online sources said that you could possibly shock the cell back to life by different methods that would be hoped to melt out the short.  It is obviously a long shot and could be pretty hazardous; especially since you have no way of knowing the real nature of the short you are dealing with.  I even once saw a home built contraption the had an inline fuse that was meant to break as soon as the switch was thrown in the hope of getting an instantaneous melting of the short while cutting out quick enough to avoid a catastrophe.  That is what I was hoping to do last some when I connected 48v to my 12v 8D last summer.  It seemed to work, but now the same cell is bad again.  I tried doing the same thing with 24v this morning.  I only succeeded in burning out both fuses in my charger.

In my experience, a bad cell does show up on the hydrometer.  For example, this battery has 5 cells that are gloriously high and one that is bad.  That bad cell did come back on the hydrometer reading when I shocked it last time.  Apparently, it is possible to get some temporary benefit from this method, but it does not solve the true cause of the problem.   If I charge the battery up now, it seems to lose about 1v per day not connected to anything else.  Another thing I have noticed is that if I open all the cells and put it on a high charger, the good cells will seriously bubble and the bad one does not bubble at all.

You are right in your warnings here.  As Garry's photo suggests, one is really playing with fire here for relatively small savings, but there is no foolishness that is beyond the consideration of anyone that would own a bus.
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buswarrior
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« Reply #34 on: January 06, 2012, 05:46:18 PM »

"but there is no foolishness that is beyond the consideration of anyone that would own a bus."

This needs to be the motto for us all.

Merchandising, cups, towels, banners, t-shirts....

Beware, we are dangerous, we own buses.

happy coaching!
buswarrior
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« Reply #35 on: January 06, 2012, 06:34:58 PM »

but there is no foolishness that is beyond the consideration of anyone that would own a bus.

  Probably true for many other hobbies or endeavors as well. I think for most reasonable people, when we have unlimited resources ($$$$$) we just keep buying everything brandy new and toss the waste behind. One the other end of life after some of those unlimited resources vanish, we start figuring out how to maintain with a smaller pile. A few years ago I didnt care, now I do. A few years ago I could have bought what I wanted, now I cant always. Luckily I learned how to scrounge and adapt when I was young and it gives me options I wouldnt have without that knowledge. Like now im much more conservative in what I buy and try to take better care of what I have. One $40 battery is one thing, $800 worth of batteries is something altogether different these days. If we can safely keep them operating there is no harm and we can save some of that unlimited resources we dont have any more.

  I have to say I never took a battery apart, I hate dealing with them enough without screwing around inside of one. I suppose there are different ways they can short internally, but as suggested the primary reason is plate contamination or warpage from excessive heat. In any case once it occurs you have a major problem. I do not believe shorting is equated to having a dead cell. My understanding is a dead cell is one that for various reasons, most likely sulfation, it is not keeping up with the others and falls off.

  A shorted battery are the ones you really need to be careful of. They can overload your charging system and burn it up. They can blow the tops off, literally explode, catch fire, or some combination. A new term of late is thermal runaway. We would all be wise to carry a bolt cutters in our bus, in an emergency it may be the fastest and only way to cut power if your battery bank goes ballistic. 
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gus
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« Reply #36 on: January 12, 2012, 01:17:06 PM »

Every battery should have a separate manual cutoff on negative battery cables to avoid just such dangers.

Bolt cutters could provide some interesting fireworks if used on positive cables!!

I just recently lost an 8D starter because its parallel mate shorted out and ruined it before I figured out the problem.
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