measuring battery drain

Rocket Science Racing rocketscienceracing at
Wed Sep 5 06:32:22 EDT 2007

Subject: Re: measuring battery drain
To: Al Streicher <streichea001 at>
> For some of us who don't understand how to measure "battery drain", could
> someone please explain.

Al: it's also very helpful to put the correct subject on your message
instead of simply replying to a random list email. I would have been happy
to chime in but in fact simply deleted your post because it carried the
subject of a mature thread I have no input on.

Here's how I do it:

1. Disconnect the battery negative cable. It's easier and safer to work on
this side of the battery, usually.
2. Obtain a digital multimeter or equiv. capable of at least 10A and set it
up to measure current on the 10A scale (if you don't understand this step it
is beyond the scope of the discussion). Radio Shack has what you need.
3. Ensure the car is off.
4. Pull the interior lighting fuse so that you can work at the fuse panel
with the door open and the interior lighting is not pulling power.
5. Attach the negative lead of the meter to the battery negative terminal. I
use a large spring clamp to hold the probe tip on it.
6. Attach the positive lead of the meter to the negative battery cable. I
used a clip lead.
7. Measure current on the meter. Be sure to wait until the load stabilizes
before starting as various systems on the car will be stabilizing for a few
seconds and the meter must be steady to get an accurate reading.
8. Pull and replace fuses one at a time noting if there is any change in the
current measurement. Record your results. Again, ensure that the load had
stabilized each time for an accurate reading.
9. Be careful not to energize any circuit that pulls more than 10A or you
will melt your meter leads or damage the meter. E.g. don't turn on the
headlights or start the car. For these tests you need a heavier duty ammeter
(something beyond what Radio Shack sells!)


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