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Author Topic:   Polarity Reversal Of Battery System
richards posted 02-18-2007 09:35 PM ET (US)   Profile for richards   Send Email to richards  
I put the battery cables on backwards. It had spark and then the hiss and then the smoke. What could be wrong with my [electrical system]?
HAPPYJIM posted 02-18-2007 10:32 PM ET (US)     Profile for HAPPYJIM  Send Email to HAPPYJIM     
In the "Electrical Trade" it is what is commonly called, "Fried".
boatsalltheway posted 02-19-2007 12:36 AM ET (US)     Profile for boatsalltheway  Send Email to boatsalltheway     
Did that with mom's Toyota Landcruiser only with jumping it instead. Alarm totally disabled it, so we unhooked the alarm, and had to replace just about every single fuse. Good luck. It shouldnt take much though if you are machanically inclined, unfortunatly we are not so the shop fixed it.
jimh posted 02-19-2007 09:34 AM ET (US)     Profile for jimh  Send Email to jimh     
When the polarity is reversed in a 12-volt battery electrical system, many devices which contain diodes will have those diodes forward biased and a very large current will flow. This generally results in the destruction of the diode junction. Some devices may be protected by a current limiting device in their branch of the circuit. If the current limiter operates before the diode is destroyed it may have protected the diode, however the damage is usually done before the current limiting device can operate.

Because of the amount of damage caused and the expense of the repairs, most people only reverse the polarity in their 12-volt battery operated electrical systems once.

Chuck Tribolet posted 02-19-2007 10:36 AM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
You have let the magic smoke out that makes electric stuff
work. You have to get it all back inside before it will
work again. ;-

You've certainly fried the diodes in the engine's charging

You may have fried the wiring between the charging system and
the battery, but if the insulation looks OK, then the wire
is probably OK (insulation cooks before copper).

Lights should be OK.

Motors are probably OK.

Electronics, well, try them and see. Some are diode protected
and will have suffered no damage.

What motor? There's a possibility you fried the ECU.


davej14 posted 02-19-2007 01:15 PM ET (US)     Profile for davej14  Send Email to davej14     
It would probably be a good idea to pull the power cables out of the rigging tunnel and check the condition of their insulation. Most diodes will fail in a shorted condition. Without primary protection on your battery cables they could have been pretty hot.

I like jimh's comment, "....most people only reverse the polarity in their 12-volt battery operated electrical systems once." That about sums it up.

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