Checking draw on battery

[super90]

How does one check the draw on the battery while the truck is off, sitting? I'm no sparky, but I was under the impression that if I disconnected the positive terminal of the battery and put the multimeter leads on the terminal and on the end of the cable, it would tell me how much current is being drawn.

Maybe my multimeter isn't working right. I got a Radio Shack 22-163 auto-range unit that the old man gifted me a while back, but I don't seem to read anything while doing the proceedure described above.

TIA.

 

[dgangle]

check on amp setting. My 15 year old Fluke has an internal replaceabnle fuse that is easy to blow if scaled incorrectly. Yours may/may not have this.

 

[kai38]

I would like to know also to see what kind of draw my fridge is pulling.

 

[dgangle]

simple google


you asked....


How to Convert Watts to Amps Simplified -- Converting Amps to Watts the easy way

 

[80t0ylc]

Here's an option for measuring current without pulling any wires:
Current clamp - Wikipedia, the free encyclopedia

If you use a regular multimeter, you must break the 12V circuit at the battery and put the meter in series, in the amps position, and run all current through the meter to measure the draw. Start in the highest current range and work your way down one position at a time until you get some meter fluctuation. The scale that your using should help you get the info you need.

 

[super90]

Mine is auto-"scaling". It does have two internal fuses that look fine. I tried the meter in series (as described in orig. post), set to amps, and don't get any readings. Meter is showing numbers slowly counting up. Not sure what that means. It happens whether the probes are touching anything or not.

Totally confused.

 

[Chaldaean]

Yes, your methods are correct.

Firstly, why are you measuring the draw on the battery while the truck is sitting? Are you testing the load from an onboard device that you want to use while the truck is off? Or, is your battery mysteriously draining and you're trying to find an unaccounted for draw; a parasitic drain?

If you're measuring the draw of an onboard device that draws a fair amount of power, your meter may not be set in the correct amperage range. It looks like your meter automatically sets itself to measure from 0mA to 40mA when you turn it on (instructions are here). That's enough range to measure a 0.48 Watt load at the most (for comparison, I would guess that a standard FZJ bulb draws 10 Watts or so; not sure). In any case, that isn't much.

Try setting your meter to manual mode and selecting a higher current range. You could also experiment with known draws (turn on your headlights or something) and see if your meter tells you anything; just to see if the meter actually works.

Does your meter display "OL" for overload or just zero?

 

[mkfour]

Measuring current is usually done by measuring the voltage across a known resistive value and then getting the value of current from there.

Since the truck is off I assume there is relatively low power draw. Insert a large resistor with proper power handling capabilities in series. Measure the voltage across the resistor with a voltmeter.

I = V/R

 

[Stereo11]

Super90, you are doing it the correct way but most meters have a socket marked for Amps you have to plug the leads into otherwise you will let the smoke out of the meter and thats bad . there should be a Black "Common" slot and two other slots, one marked "Amps" and the other "Volts" Check the pic

 

[WarDamnEagle]

Measuring current is usually done by measuring the voltage across a known resistive value and then getting the value of current from there.

Since the truck is off I assume there is relatively low power draw. Insert a large resistor with proper power handling capabilities in series. Measure the voltage across the resistor with a voltmeter.

I = V/R

You don't have to do it that way if you disconnect one of the battery leads and put an ammeter in series with the battery and the disconnected lead. I suspect the OP either is not using the AMP connection (as Stero11 suggested) or the meter doesn't go low enough to read the current draw.

Others have already posted good links but here's another:

Ammeter usage : BASIC CONCEPTS AND TEST EQUIPMENT

 

[super90]

Yes, your methods are correct.

Firstly, why are you measuring the draw on the battery while the truck is sitting? Are you testing the load from an onboard device that you want to use while the truck is off? Or, is your battery mysteriously draining and you're trying to find an unaccounted for draw; a parasitic drain?...


....Does your meter display "OL" for overload or just zero?

Yes the battery just "died" the other day while I was sitting, having a cheeseburger. I am wondering is something is draining it while it is sitting. It did seem like it wasn't spinning the starter as fast the past few days, and then, dead. So, maybe there is just something wrong with the battery, and not something draining it. Just wanted to check to make sure. Put the battery on a trickle charger overnight, and going to have it load tested today.

No "OL" displayed.

FYI, I am testing with a new battery in the truck. The DieHard Platinum Group 31 mentioned in another thread.