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Charge battery backwards?

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Dave (IL)

01-03-2005 07:23:24

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Is it possible to charge a battery backwards?
Take a dead battery, put the charger on backwards and actually get a charge with reversed polarity?

I don't think so, but I thought I'd pose it to the collective experts.

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01-03-2005 17:02:03

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Re: Charge battery backwards? in reply to Dave (IL), 01-03-2005 07:23:24

Interesting question, don't know the answer, won't find out. My charger does not allow reverse charge, instructions say will damage charger. In the meantime I'll take other's experience as the fact.

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farmalljim10

01-03-2005 12:04:43

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Re: Charge battery backwards? in reply to Dave (IL), 01-03-2005 07:23:24

Yes you can charge them backwards. My father used to do it all the time ..On purpose... What he said killed most batteries was shorts betueen the plates at the bottom of the plates..So he would completely dis charge a battery and then recharge them backwards so as to make all the stuff on the bottom of the plates switch from pne plate to another then discharge it again and recharge it back to normal... Now did it work? Well yes sometimes it did and sometimes not..But you really have to have a lot of time..

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greenbeanman

01-03-2005 09:51:48

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Re: Charge battery backwards? in reply to Dave (IL), 01-03-2005 07:23:24

I was taught in mechanics class in the mid '60s that there is an odd number of plates in a battery, which therefore allow/send the current in only one direction. All of you sure seem to know more about it than the teacher did. Having done it first hand---I'll take your word on it rather than the teachers.

Interesting question though.

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Bob

01-03-2005 09:58:09

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Re: Charge battery backwards? in reply to greenbeanman, 01-03-2005 09:51:48

Greener,

Nothing to be smart about. Whether or not is supposed to happen, it can and DOES. A couple of the reversed-polarity batteries I've had experience with had enough capacity to start the engines quite well, although I did not load test them, for an exact cranking amps number.

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greenbeanman

01-04-2005 09:41:31

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Re: Charge battery backwards? in reply to Bob, 01-03-2005 09:58:09

I think that my dad may have charged up some MM GVI batteries backward when he was in his late 80s. He couldn't get the tractor started and asked me to check it for him. When attempting to start, the radiator fan appeared to me to be turning backwards. I checked the battery for polarity and it was correct, i.e. positive cable on positive battery post. The engine turned over much slower than it should have as well.

I finally took the battery out and put in a battery from our G705. The tractor started right up. I don't remember which direction the fan was turning.

I also don't remember the final outcome as to whether we put in a different battery or what.

Sure makes sense though now that I think about it.

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buickanddeere

01-03-2005 08:58:43

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Re: Charge battery backwards? in reply to Dave (IL), 01-03-2005 07:23:24

It was common in the old days of generators. Dead vehicle, usually with a positive ground system or a tinkerer who can't read. Gets boosted reverse polarity and starts. Battery is so low it doesn't smoke the generator and the generator has it's polarity changed faster than the cut-out in the regulator can open. The machine may even run for some time but cold starts will be poorer. From reverse ignition polarity and a weaked battery. Now when a fresh fully charged battery is installed with correct polarity. Everyone wonders why the generator failed right away. Or they think the generator had failed a short time before the battery went dead.

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Dave (IL)

01-03-2005 09:15:01

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Re: Charge battery backwards? in reply to buickanddeere, 01-03-2005 08:58:43

In your example it's the genny that reverses, correct? The battery polarity is retained.
If the tractor were pulled rather than jumped, couldn't the genny stay the same and the battery get charged backwards?

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buickanddeere

01-03-2005 12:13:41

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Re: Charge battery backwards? in reply to Dave (IL), 01-03-2005 09:15:01

The generator can get reversed if boosted backwards with dead battery. It will get flashed in to match the polarity of the boost once the engine is reved up. A fully charged battery installed reverse polarity can let the smoke out of the generator wires when the cut-out closes. Othertimes the cut-out contact fries. And sometimes the generator takes a nasty surge and gets repolarized. If pull started with a reversed dead battery then yes the tractor's polarity should stay the same and the battery become charged in reverse.

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Bob

01-03-2005 09:23:09

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Re: Charge battery backwards? in reply to Dave (IL), 01-03-2005 09:15:01

Dave,

Your scenario is certainly possible.

Drain the battery by hooking a a spare headlite to it until it's dead. Recharge it with the proper polarity. Connect it properly to the tractor. Polarize the generator. Start it up, and check it out.

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Dave (IL)

01-03-2005 09:43:36

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Re: Charge battery backwards? in reply to Bob, 01-03-2005 09:23:09

I don't have a current problem like that. Just got to thinking about whether it could happen.
I did buy an H about a year and a half ago. It was a little troublesome over the first winter but a charger kept things workable. When I went over it in the spring, I realized the prev owner had the battery in backwards. I flipped it and flashed the field and it's been good since.

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James Herrman

01-03-2005 22:24:07

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Re: Charge battery backwards? in reply to Dave (IL), 01-03-2005 09:43:36

Yes it can happen and in fact I have done it. When a battery gets almost dead, when you put a charger on it, it can go either way. I have also tried to drain the battery with a light and also have hooked another battery in line with it, but it seemed to me that once a reverse charge starts to take, I have been unable to reverse the process. JIM

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NEsota

01-04-2005 08:38:05

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Re: Charge battery backwards? in reply to James Herrman, 01-03-2005 22:24:07

Sure you can charge a battery backwards but it will at once, be considerably less efficient. When a battery is charged and discharged the spongy lead and other material on the plates expands and contracts. The deeper the cycle the greater the change. Deep cycles shorten battery life because the active material on the plates sheads off faster due to the increased expantion-contraction. This reduces plate size and capacity. In a reverse charge, this change will be even greater than in full discharge. Deep cycle batteries are built useing material on the plates to minumize the effects of expantion-contraction

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Dave (IL)

01-03-2005 08:18:55

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Re: Charge battery backwards? in reply to Dave (IL), 01-03-2005 07:23:24

Thanks. Apologize for not searching first. Been hanging around here for almost 2 months but guess I wasn't going to N forum at that time.
Been a long time since I delved into the chemistry of it all and can't say as I'm real motivated to do it now.

So if you took an old H with 6pos, accidentally put a deadish battery in backwards and didn't flash, the genny could still be putting out the other way and charge it backwards?

It does point out one more thing to check when chasing bizzare problems.

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Ludwig

01-03-2005 14:51:16

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Re: Charge battery backwards? in reply to Dave (IL), 01-03-2005 08:18:55

Actually what you'll do there is ruin the regulator. I'll get all confused about what you're trying to do and just give up.
Been there, done that on a Super M.

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old

01-03-2005 08:05:15

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Re: Charge battery backwards? in reply to Dave (IL), 01-03-2005 07:23:24

If the battery is dead it doesn't care which way you charge it but after that its not very good any more. I've done it a few times and ended up with a core battery

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Bob

01-03-2005 07:47:46

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Re: Charge battery backwards? in reply to Dave (IL), 01-03-2005 07:23:24

I've seen it happen two or three times. YES, it's possible.

Link

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Coloken

01-03-2005 07:44:07

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Re: Charge battery backwards? in reply to Dave (IL), 01-03-2005 07:23:24

Yes. I have done it several times. Don't think it is too good for the battery. You can just live with it that way or complatly discharge it and re-charge it the right way.

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