Gale Hawkins
Murray, KY
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WARNING: I am making this edit to make sure I am not stating to do this and is only research results from some research on the subject relating to someone applying for a patent on the process. Summary of my research is it can be done BUT IS NOT WORTH THE EFFORT OR RISK in a practical sense. That info link is in a post about 7 below this first post. We currently own and keep charged 115 lead acid batteries between home and the office so batteries have my attention because they have my billfold. 
I had two banks of four DC-27 batteries that I had set to the side dated 2007 and 2010. I would charge them and in about a month or two they would be reading 5-6 volts each.
I cabled the posts for a few days then that would get them down to about 2 volts after removing the direct short for a few hours. I could not fully discharge these batteries by a dead short for days at a time.
Then for a few days I reversed charged them with a manual charger that did not complain TOO much. This took a while because even to the 3 amp setting the charger would output up to 200 amps even on 6v setting initally.
After frying an old DC-24 set a few years ago I did not reverse these two sets all the way to 12 volts this time. The other time I got them to reverse and hold 12 volts but when I tried to flip them back to OEM state they DIED HARD.
After working with with this last two sets for days I got them where they I could reverse charge them at up to 15 volts for short periods until they would not flip back to OEM polarity but show .1v to zero after setting overnight.
It is next to impossible to get the polarity of a DC battery to reverse in my experience.
After days of off and on reverse charging and basically getting them to ZERO volts after setting overnight I started charging them with the correct OEM polarity. That is the easy part.
At first they want to max out the manual charger but that does not last too long but it took a few days of slow charging before the three stage B&D chargers would not error out from time to time so I would run them in Desulf Mode and use manual chargers.
Even though all cells would gas when reverse charging I had one in each of the two banks of four that would go to 10.5 volts setting overnight after the double polarity flip so I lost those two to dead cells.
Using the HF load tester I know the three out of the 2010 group will go days and still be at 12.5 volts unlike before the reverse charging treatment and are testing out OK when load testing. The 2007 set of three remaining batteries are not not doing so hot but under the 10 second 100 amp load they are no longer testing BAD like after first getting them flipped back. I did the other set first so I am going to play with them for another week or so since they are gaining some per the HF battery tester.
We picked up the 45 watt HF solar system as a class project for the kids so I am trying to see if I could recover these batteries that had dropped below 50% of their new run time as a 48v bank for the server room UPS. New they will last about 60 minutes and after capacity drops to 50% run time goes over the clift.
I use the same size batteries in the MH. These batteries are WM but the current set in service since last OCT are Interstate.
While I was able to recover 3 of the 8 to usable condition and the remaining three to a lesser degree time wise it is not worth the effort. Basically after researching this a few years ago and failing I wanted to build off of the knowledge/experience and see if I could do it.
Summary: Took 4 2007 and 4 2010 WM branded DC-27 batteries that would drop to about 5-6 volts after a month. By reverse charging I slightly flipped the polarity to the point over night polarity would not revert to OEM polarity then I recharged them using the correct polarity. The hard work was done by 6/12 volt manual wheeled charger with 200 amp boost feature. The research I read indicated a 20-24 volt charger would be more effective in such a project. 6 of the 8 are OK to some degree and two had a dead cell each that did not recover from the reverse polarity battery recondition process.
* This post was
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ScottG
Bothell Wa.
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Joined: 02/25/2005
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I keep thinking of a dopey kid I knew as a teenager who tried to jump start his car but reversed the polarity of the jumper cables. It blew the top of his battery off and sprayed him with acid.
Scott, Grace and Wesly
2003 Dodge 3500 4x4, 6 speed Cummins (lightly bombed),
2004 Forest River 25RKS many, many mods.
H0NDA eu2000i
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Golden_HVAC
Fulltime, CA, USA
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Can you add water to these batteries?
Why not add some EDTA? Home Power Magazine did this to a few batteries, and was able to bring them back from very low voltage.
Don't know why it works, just that according to Home Power testers it is working.
Fred.
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Gale Hawkins
Murray, KY
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ScottG wrote:I keep thinking of a dopey kid I knew as a teenager who tried to jump start his car but reversed the polarity of the jumper cables. It blew the top of his battery off and sprayed him with acid.
My FIL did this and drove the truck back home and took roofing tar and resealed it and used the battery for several more years. 
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Gale Hawkins
Murray, KY
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Golden_HVAC wrote:Can you add water to these batteries?
Why not add some EDTA? Home Power Magazine did this to a few batteries, and was able to bring them back from very low voltage.
Don't know why it works, just that according to Home Power testers it is working.
Fred.
That would have made the polarity reversing for sulfate removable test results invalid.
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ScottG
Bothell Wa.
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Gale Hawkins wrote:ScottG wrote:I keep thinking of a dopey kid I knew as a teenager who tried to jump start his car but reversed the polarity of the jumper cables. It blew the top of his battery off and sprayed him with acid.
My FIL did this and drove the truck back home and took roofing tar and resealed it and used the battery for several more years.
Good for him - you gotta appreciate guys like that!
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old guy
Oregon (pronounced Or e gun)
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I did a stupid thing one time. I hooked up the batteries back wards and the darn things lost all their voltage. Had to buy new ones.
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Gale Hawkins
Murray, KY
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This is where I got my first info on desulfation by reversing polarity.
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wa8yxm
Wherever I happen to park
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Joined: 07/04/2006
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I remember once helping a stump removal crew start their truck,,, They had tried to jump start the stumper with the truck, I ask them if they hooked positive to positive and negative to negative (knowing they did not) and they said "We hooked hot to hot and ground to groudn how much more positive to positive can you get?
24 volts
You see, the stumper was POSITIVE ground.
(The truck negative ground like most American vehicles).
Having driven an ENGLISH ford I knew about positive ground.
You can jump start a positive ground stumper, but NOT from the truck towing it.
Nothin adds excitment like something that is none of your business
Kenwood TS-2000 housed in a 2005 Damon Intruder 377
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3 tons
CA.
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Sounds hazardous...
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