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Old 09-15-2008
patja patja is offline
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Ground leak?

I am evaluating a potential ground leak and could use a second or third set of eyes on the situation.

I've removed all positive cables from the batteries, and the only negative connection is to the grounding system...to the engine and then grounding wires to thru-hulls, props, tanks, etc. All breakers are off, and the shorepower cord is disconnected.

My observations under the above conditions:

I am getting a 12V reading between the positive battery terminal and the disconnected positive cable. This is always cited as the primary indicator of a leak.

The resistance is fairly high, about 100,000 Ohms, between the negative battery terminal and the disconnected positive cable.

When measuring the current flow across the positive battery terminal and disconnected positive cable, my multimeter gives an initial reading of 90 milliamps for a few seconds, then it drops down to about 2 milliamps.

First question: do I really have a problem or not? Casey and Calder say ground leaks are only "serious" with a resistance of under 10,000 Ohms. But then again, they also say that all leaks greater than 5 milliamps must be eliminated.

Is my leak 2 milliamps or 90?

The boat is fairly new to me so I don't have the history, but my divers did just replace my zincs at 50% after only 3 months.

Thanks in advance for any helpful insight!
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