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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