A safe and accurate method of measuring parasitic draw involves a 1.0-ohm, 10-watt resistor. The resistor is placed in series between the negative battery terminal and the negative battery cable to dynamically test parasitic draw. The key-off battery drain passes through the resistor, while battery voltage is allowed to stress the electronic components on the vehicle. Very little current passes through the meter, so there’s no risk of meter damage.
With the ignition off, placing the test leads of a digital voltmeter on either side of the resistor measures the voltage drop across the resistor. Using Ohm’s law, we know the measured voltage drop is a direct reflection of the current flow or parasitic draw that’s present. So a reading of .02 volt on our meter indicates a .02-amp (20mA) key-off battery drain.
I agree with you as thats a safe way to do it but my Fluke does have a protection fuse that will blow if I would forget and do something dumb like turn the key on with the blower on high. But I do use my fluke in series with the battery and cable all the time to check draws and I like how it reads just what it see's in milli-amps. But you are right for someone who does not do this alot for a living as the way you have shown is safer on the meter and will work. Myself I prefer how I do it but this is good that you have posted to show how the draw can be checked this way and its safe on the meter. Ron
