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Battery Polarity Reversal

10/29/2009 5:45 PM

I had a problem a few years ago. Still trying to find out how.

60 Ah/12 volt car battery on my Peugeot 504 have totally flattened due the ceiling lamp have forgotten switched on for a week, during the car has left in the parkplace in the airport.

I hadn't got a battery charger , therefore removed the battery and sent to a local repair service for recharging.

A day after the battery came back recharged. I put it on my car, taking care for polarity. (Wrong connection is impossible because the connectors are different sized)

As soon as I completed the connection, a strong spark is occured and some smoke rise in the alternator.

Then I checked the voltage across the battery terminals. The voltage is O.K, however the polarity of the battery has reversed. + terminal shows - and - shows + even opposite is marked on the battery box.

Supply cables to alternator have burnt out, as well as the diode bridge rectifier have gone.

I got repaired the alternator and the burnt cables. For a quick solution, I have turned around the battery to let the correct pole to correct side. replaced the battery connectors each to opposite side, to enable them to fit the battery output plugs. Therefore the car was working O.K. The only difference was the battery was working with reverse polarity.

It went out two more years with the wrong polarity, until the day I left the car in the parkplace, the radio is switched on.

Of course the battery flattened to zero again in few days as before.

I did not send the battery again for recharging. This time I had a battery charger therefore I did not send the battery for recharging. I checked the polarity before connection to charger. Big Surprise. battery came again to correct polarity.

I charged the battery as it has to be. Now that the polarity is correct , I replaced again the battery connectors coming from car. . Give a start to the engine and everything is O.K again.

Still could not explain how the battery polarity reversed when completely discharged to zero voltage. Does anyone have any idea?

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Anonymous Poster
#1

Re: Battery polarity reversed

10/29/2009 6:23 PM

whoever charged the battery at the shop hooked up the battery charger backwards. this caused exactly what you experienced - reverse polarity. the only way to correct this after having done it is to completely dis-charge the battery and correctly connect the charger. your own experience tells you this is true. i've been a mechanic for more years than i care to think about and i've seen this happen more than once.

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#2

Re: Battery polarity reversed

10/29/2009 9:35 PM

Lead-acid Batteries are built using lead plates for positive and negative electrodes. Unlike other batteries that use dissimilar metals. When charging the battery, the plates combine with the acid to make the plates somehow dissimilar. I don't remember the exact chemical reaction as I learned this 50+ years ago, but You can google lead-acid batteries and probably find all the info you could possible want to know.

Because the plates are made from the same material (Lead or lead mixed with small amounts of other metals, The polarity is determined by the polarity of the charging current. Therefore you can charge a totally flat battery in either direction (polarity)

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#3

Re: Battery polarity reversed

10/30/2009 7:37 AM

The last person that touched it screwed it up. In your case it was the people that charged your battery the first time it was dead.

As stated above, you corrected the problem by your actions.

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Anonymous Poster
#4
In reply to #3

Re: Battery polarity reversed

10/30/2009 8:17 AM

Thanks guys. Thanks everybody.

Even all those screwing operations have happened, the subject battery have gone five years. Three total years with correct polarity and two years with reverse polarity.

It was a Warta. I am sure this battery is owing his long life to my seldom usage for the car. A few engine start in the complete week.

Eventually, the car have been sold with the same battery fitted on. Battery was still operational.

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#11
In reply to #4

Re: Battery polarity reversed

11/02/2009 6:00 AM

Did you tell the idiots who charged it backwards what they'd done? +ve and -ve are clearly marked on a battery. If they were anything like reasonable they would have paid for your alternator repairs.

Cheers...........Codey

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Power-User

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#13
In reply to #11

Re: Battery polarity reversed

11/02/2009 6:46 AM

I did. They did not believe a battery could be reversed.

I asked them to check the battery.

They checked. They satisfied. However they paid nothing.

They told that they do not have any official responsibility for each battery, of which coming them for recharging.

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#14
In reply to #13

Re: Battery polarity reversed

11/02/2009 6:59 AM

Crooks. I trust you won't be dealing with them again.

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#5

Re: Battery Polarity Reversal

10/31/2009 9:02 AM

Interesting. I recently was checking a dozen or so used AA batteries that over a period of months came from various electronic devices (remotes, kid's toys, etc.). I suspected some might still be usable. Most were dead, a few were still good enough to use, but 3 had a negative voltage on it. And yes, I was connecting the leads of the DVM to the correct terminals of the batteries. They are not rechargeable type batteries either. My theory is that they were installed in one of the devices backwards opposing a larger number of batteries. I can't really imagine why the devices would have been working if configured that way, but I can't think of any other way for the batteries to reverse polarity. Is it possible they they were that way from the from the manufacturer?

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#8
In reply to #5

Re: Battery Polarity Reversal

11/01/2009 6:39 PM

Your small, non-rechargeable batts probably got charged in reverse by leaving the torch or radio on when the batts went flat. the batts are never exactly the same therefore when the first one reaches zero the remainder still have some charge and now they will pass charge current in the wrong direction.

Chas

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#9
In reply to #8

Re: Battery Polarity Reversal

11/01/2009 11:23 PM

Chas,

Thank you. I hadn't thought of that.

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#6

Re: Battery Polarity Reversal

10/31/2009 11:44 AM

It would make a fascinating experiment to see if periodically reversing the charge on a lead-acid battery would extend the service life. Could be a great cost saver for golf cart and home windmill installations.

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Power-User

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#7
In reply to #6

Re: Battery Polarity Reversal

10/31/2009 12:50 PM

Exactly it's funny but correct, experimentally proved.

I am sure this rule is written nowhere.

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Active Contributor

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#10
In reply to #6

Re: Battery Polarity Reversal

11/01/2009 11:35 PM

Reversing polarity would be an interesting experiment since discharging a lead acid battery usually destroys it.

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#12
In reply to #10

Re: Battery Polarity Reversal

11/02/2009 6:39 AM

Of course trying to reverse the polarity of a semi or fully charged battery results catastroph. Trying to recharge in reverse way draws more current than the short circuit. (Twice of the short circuited amps, however the current is limited somehow on the conductor loop) First the rectifying diodes for the charger blows off.

The battery was totally flattened with zero voltage during they reversed.

Kindest Regards

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#15
In reply to #6

Re: Battery Polarity Reversal

11/04/2009 12:57 AM

i was thinking/wondering that exact thing when i saw the service life he got out of his battery.

.

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