Quote:
Originally Posted by Thomas G.
I think that it is just a digital voltage meter.
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That's exactly what it is. They are using the lighter plug for convenience. I prefer a multimeter on the battery. That said, the advantage to this gadget is that you can leave it plugged in all the time and you will be more likely to look at it. You've got to remember to use the meter.
Carols has the addition of a comparitor circuit to compare the reading to a preset value, probably about 12.2 volts, and then trigger the alarm. More info than you needed I'm sure.