amperes measure?

Question

Need to measure drain on 12volt car battery when ignition and accesories turned off.
Will use multimeter to measure, probably in miliamps.
Need to know how to connect to system without burning up or damaging meter. Thanks.

Answer 1

disconnect ur positive cable use multimeter between positive cable and positive battery post this will tell u the draw if any be carefull to use the proper seting on multimeter or u can burn it up

Answer 2

CAUTION: Mr. drvshaftdrew is incorrect; one should disconnect the negative cable and work from there. This is very standard practice in the automotive industry. One should always start with the negative (-) lead when disconnecting a battery. The ONLY exception is if your vehicle is a positive ground system; in which case the advice is opposite on all counts.

R1volta has a very detailed academic presentation which will give you specific connection details. In short, Meter Plus (10A fused) to the disconnected ground cable, and Meter Minus to the negative battery terminal.

One caution, make sure you use a multimeter with at least a 10 amp scale that is also fused. All that has to happen is to have one door open and you can burn out a meter set on a lower scale. In fact, 10 amps might not be enough so be prepared to disconnect quickly if the meter jumps off the scale when you make the connection. For example, my old Fleetwood Brougham had about 8 lights that would come on if any door was opened; ie, easily 12 amps!

If you're curious about car batteries in general, the Wikipedia link is below.

P.S. Be careful if you have a radio with a security code or if your car has an emissions computer (most do since mid-70's). Record your security code in case you need it to re-enable your radio. And be sure to drive the car around for a couple days after this procedure before going to any emissions tests or you may fail the test and have to come back (and at $27 a pop in NY that gets expensive quick).

Answer 3

Even better than using a milliamp meter try a test light . Put the test light in betwwen the positive or negetive and battery post and if it lights, you have too big of a drain, if it doesn't light you are probably OK. Most new cars always draw some small amount to keep computers and memory devices alive. If the light is lit start pulling fuses until it goes out and then you will have your faulty circut. This trick also works with a voltmeter (it's the only time you put a volt meter in series) if the meter reads 12 volts again pull fuses until it drops (it may only drop to 9-11 volts) but as long as it isn't 12 volts you have found your faulty circut

Answer 4

If you wish to measure milliamps you disconnect the negative terminal then measure from it to the positive battery post. Do not disconnect positive terminal.This will tell you if any amps are flowibg.

Answer 5

www.umd.umich.edu/casl/natsci/slc/slconline/DIG/DIG2.ppt
This web site will help you.