[svxcess]

Originally Posted by Trevor

If you are fitting a permanent voltmeter, do it properly. Run a voltage sensing wire, via a one amp in line fuse, close to and connected to the main battery positive terminal. This wire can be of small cross section, as a meter should draw negligible current. Voltage readings will then be independent of any subsequent loads and always reliably accurate. The degree of satisfaction will surely make it worthwhile.

Trevor,

I totally agree about the parallel loads and increased line resistance. I found that the voltage measurements at the cigarette lighter socket are about 0.9V lower across the board than taking the measurements directly at the battery. I think that the heating element of the lighter has created corrosion and resistance in the wire that feeds it.

Also the wire to the lighter is impossible to inspect for corrosion or a weak connection.

That is why I mentioned the following in the opening lines of my Alternator Testing Procedure post:

Using a 12V power socket with two battery clamps at the other end, I connected the socket directly to the POS and NEG terminals of my battery and plugged in my Nordskog digital voltmeter. The battery had the additional, upgraded 4 gauge power and ground wires attached.

I believe that by connecting the meter as close to the alternator as possible, I would get the most accurate readings. Since there is only one wire directly from the alternator output terminal to the battery, this would be the optimum location for testing.

So the alternator output to the battery was checked at the battery, through a 3 gauge wire run of about 18".

In the future I may just cut the wire from the back of the cigarette lighter and measure the resistance between the end of the wire and the POS connection inside the lighter. If it is close to being around 0Ω, I may just splice a wire directly to the battery for the voltmeter. (I just have to remember to unplug it when not in use as the socket would be hot all the time.)

The easiest and laziest thing to do is use the voltmeter in the existing lighter socket and remind myself that a reading of 12.9V is really 13.8V.


But we all know that svxcess neither takes the easy nor lazy way out on anything...

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