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John Perz

The dealer measured the voltage at the house battery with the truck running and said voltage was good. I don’t know enough about it to argue with them

A little background information for you: A 12 volt battery consists of 6 cells, each of which is approximately 2.1 volts. So a fully charged 12 volt battery will actually read 12.6 to 12.7 volts when fully charged. In order to charge a battery, the system must deliver a higher voltage than that. So when the truck is not running, the house battery should measure 12 to 12.7 volts. When the truck IS running, if it’s charging the house battery, you should read 13 to 15 volts, with 14.4 to 14.6 being more or less the ideal range for a battery. If, with the truck running, you are only reading 12 to 12.7 volts, the truck is NOT charging the battery. A simple meter from Harbor Freight ($5 -$10) is all you need to check this.

You can measure your engine starting battery both with and without the truck running to see what I mean and to see what your charging voltage actually is.

As for your long charging wire, too long a run of too thin a wire causes a voltage drop, which leads to less amps flowing and means it takes longer to charge the battery.

Hope this background info helps.

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