This is EE101 applied to a car battery being discharged when the car is parked
and not driven & isolating the current drain circuit when not obvious. With
battery shutoff switch and lack of fused circuits it is not as applicable to
AH as to others but it is definitely a procedure to remember, for shorts,
electric device current draw (not starter), etc. Also the double connectors in
the AH can isolate circuits as per elec. diagram.
Go to a Radio Shack & buy a
2 pack of 1.0 ohm, 10 watt resistors.
http://www.radioshack.com/product/index.jsp?productId=2062290 They cost
$1.99. Wrap the leads of the 2 resistors together(wiring in Parallel)to make
a 1/2 ohm resistor and then attach a alligator clip to each end, big enough to
clamp on the ungrounded battery post (after disconnecting that battery
cable. Note: battery disconnect switch should be 'on' and ign. switch 'off'.
Connect one alligator clip to the battery anode and the other alligator clip
to the removed battery cable( best to be on 'hot' post not ground). This will
put a .5 ohm resistor in series with the removed battery cable. You
absolutely have to have a voltmeter of some sort, a good digital vom is dirt
cheap. Set the voltmeter controls to measure voltage, connect one lead of the
VOM to the battery alligator clip and the other battery lead to the + cable
alligator clip(parallel with the resistors).
Using ohms law I=E/R where R
will be .5 ohms wired as shown, just reading voltmeter will tell you how much
current draw you have from a short or something left on . For example, if the
voltmeter reads 5 volts, 5V/.5ohm= 10A current draw. Then start pulling
fuses; when you pull the right fuse the voltage will drop drastically,; look
for a problem in this circuit.
If no change or very little change in voltage
when you pull a fuse or connector, it's the wrong circuit.
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