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Author Topic:   Predicting Damage Caused By Improper Connection of Boat Wiring to Boat Battery
David Jenkins posted 04-12-2010 11:24 PM ET (US)   Profile for David Jenkins   Send Email to David Jenkins  
I hired someone to help me get my boat clean and ready for the boating season. He wanted to do such a good job cleaning that he removed the battery from the boat. When he re-connected the battery he put both the positive and negative leads from the engine onto the positive side of the battery. He also put the positive accessory line onto the negative side of the battery. It stayed this way for about an hour. At that point I came home, saw what he had done, and straightened out the wires. Should I be worried? How will I know if damage has been done?
Chuck Tribolet posted 04-13-2010 09:00 AM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Make darn sure he knows NOW what he did, and that you hold him
responsible for any damage.

Did you catch it before turning on the ignition or Acc
switch? If yes, probably no damage.

If no, It's really hard to guess what might be damaged. The
instruments may got a reversed power supply and that may or may
not have caused damage. Fix the wiring, and see what works.
The more expensive stuff (GPS, etc), is probably diode
protected and OK. The rectifier in the engine probably did
not get a reverse polarity (because both engine leads were
on the same pole, it got NO polarity).

There's a pretty good chance you came out of this clean.


David Jenkins posted 04-13-2010 09:36 AM ET (US)     Profile for David Jenkins  Send Email to David Jenkins     
That is reassuring. Thanks. The ignition was not turned on while the wires were in the wrong places. And no accessories were connected.
Jerry Townsend posted 04-13-2010 10:45 AM ET (US)     Profile for Jerry Townsend  Send Email to Jerry Townsend     
You are just fine - even if you turned a switch on - because with both connectors/wires connected to either the positive or negative post on the battery, there is no current flow. ---- Jerry/Idaho
davej14 posted 04-13-2010 11:14 AM ET (US)     Profile for davej14  Send Email to davej14     
Note that the accessories were wired with reverse polarity. The only reason you did not sustain damage to the accessories is that you did not have them connected. May the "force" continue to be with you !!
Bella con23 posted 04-13-2010 11:50 AM ET (US)     Profile for Bella con23  Send Email to Bella con23     
If I read the original post correctly, David said both starter leads were wired to the same post but the accessory leads were wired positive to negative and negative to positive of the battery.

If this is the case refer to Chucks answer.

David Jenkins posted 04-13-2010 01:02 PM ET (US)     Profile for David Jenkins  Send Email to David Jenkins     
The only wires connected to the positive side of the battery were the two big cables coming from the engine. All of the other (smaller) wires were connected to the negative side of the battery.
bluewaterpirate posted 04-13-2010 02:01 PM ET (US)     Profile for bluewaterpirate  Send Email to bluewaterpirate     
Did he have his green card?
davej14 posted 04-13-2010 06:26 PM ET (US)     Profile for davej14  Send Email to davej14     
This makes a good case for having a battery switch that you habitually leave in the OFF position.
contender posted 04-13-2010 06:39 PM ET (US)     Profile for contender  Send Email to contender     
Jerry is correct, If what you said is the way it was connected you lucked out, there was no current going through the electrical system unless you have another ground somewhere...
jimh posted 04-14-2010 09:04 PM ET (US)     Profile for jimh  Send Email to jimh     
Interpreting the narrative of the connection problems, I conclude:

The primary positive and negative distribution circuits were both connected to the battery positive terminal.

A secondary positive distribution circuit was connected to the battery negative.

The effect of this would be:

--for devices whose source of electrical current was the primary distribution circuit, there was 0-volts of electrical potential, and no current would flow;

--for devices whose source of electrical current was the secondary distribution circuit connected accidently to the battery negative, there was -12-volts of electrical potential--the opposite polarity from normal. Depending on what devices were connected to this circuit, how those devices are configured, and how any over-current protection is provided, it is possible that a large reverse current could flow, possibly blowing a fuse or other over-current protection device. Without knowing the details of all the devices connected to this circuit, it is impossible to assess the damage potential.

jimh posted 04-17-2010 10:15 AM ET (US)     Profile for jimh  Send Email to jimh     
Damage to electrical circuits which results from a polarity reversal in the power supplied to them generally takes the form of excessive current flow in portions of the circuit or in devices in the circuit where the reverse-bias on rectifiers creates an unusual current path. Detection of damage from high current can often be made by:

--noting effects of the high temperatures created by the high current, such as discoloration, melting, or other distortion of the conductors and devices;

--finding a permanent opening of the circuit where conductors have melted or where semiconductors have been destroyed and failed into open circuits;

--finding a permanent short in the circuit where conductor have melted and created new circuit paths or where semiconductors have been destroyed and failed into a short circuit

--noting unusual smells from some devices where high temperatures have caused combustion or burning of the plastic materials associated with the devices

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