Help reading multimeter

Thread Starter

Gandyc

Joined Oct 29, 2022
2
Can someone help me figure out what the meter is reading in this photo?

I've got the meter inline with the negative terminal on my car battery, trying to see what the car is drawing while turned off (having battery problems.)

This meter is confusing to me for some reason...

Thanks!!!
 

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Reloadron

Joined Jan 15, 2015
7,079
Looks to me like 0.11 mA or about 110 uA not much at all. Really no load to speak of on the battery. This assumes the meter red is on + battery terminal and the black is on the lead which is removed from battery + terminal. The meter is in series with the load.

Ron
 

BobTPH

Joined Jun 5, 2013
6,077
I am surprised it is that low. Have you tested the meter on a known current? Measure current through a 100 Ohm resistor in series with the battery and ir should be 120mA.
 

Thread Starter

Gandyc

Joined Oct 29, 2022
2
I am surprised it is that low. Have you tested the meter on a known current? Measure current through a 100 Ohm resistor in series with the battery and ir should be 120mA.
Yes, I’m with you. Unfortunately, I don’t have a resistor.

For what it’s worth, the AC volt setting works fine tested on a non-good outlet.
 

MrChips

Joined Oct 2, 2009
27,679
The meter is showing 0.11mA.
This may not seem like a relevant question but what is the make, model and year of the car?
With all the electronics on newer cars, the parasitic current draw can be 20-80mA.
 

MrSalts

Joined Apr 2, 2020
2,617
Are you just connecting the multimeter between the + and - of the car battery? If so, you've likely blown the fuse on the meter and your seeing some noise of 110 microamps.

if, on the other hand, you disconnected one terminal in the car battery and connected your amp meter between the battery terminal and the disconnected cable, then you are measuring the parasitic current of all the various electronics in your car in idle/ready state like the alarm, keyless entry and so on.

note: if you simply connected + and - terminals with your meter, and you were on the DC mA setting as shown, you're in luck because you likely only blew the fuse (you should should keep below 200mA according to the front panel of your meter). On the other hand, if you were to switch to DC amps, that input is not fused (unfused) according to the front panel. If you would have switched to that input, it is possible that you would smell burnt plastic, felt the meter get warm and had an unhappy day in several other ways.
Please post about how you connected your amp meter to your battery.
 
Last edited:

Externet

Joined Nov 29, 2005
1,960
With key on ACC position, turning on the radio at zero volume should show a higher current if no resistor on hand.

BAT+------------------------+meter-------------------------+cable-----------------------to all drains-----------------------------GND
 

Ian0

Joined Aug 7, 2020
6,706
When you have replaced the fuse. . .
Try connecting the probes to the cable and to the battery whist the cable is still attached to the battery (by holding the black probe against the terminal) then removing the cable with the probes still connected. That stops the inrush into all the electronics blowing the fuse.
 

BobTPH

Joined Jun 5, 2013
6,077
Before doing anything else, switch to the 10A range. Be sure to move the red probe to the special socket for that range.
 

Ian0

Joined Aug 7, 2020
6,706
When you have finished, move the probes back to the Voltage sockets, before you accidentally measure the current from the mains and need a new meter.
 

MrSalts

Joined Apr 2, 2020
2,617
And never connect the probes directly to the - and + of a battery or power supply. Disconnect one battery terminal and then connect one probe to + battery terminal and the other to the disconnected cable.
 

Ian0

Joined Aug 7, 2020
6,706
That's quite a dangerous multimeter. If I had one with voltage and current on the same sockets, selected by a switch, it would be dead in no time.
 

Reloadron

Joined Jan 15, 2015
7,079
Slightly off topic and a little humorous. Years ago, many years ago, my mom had a little Buick and mom seldom went anywhere sometimes for a week at a time. The battery kept going about dead. My dad was getting annoyed and then suddenly the car by a miracle healed itself. Mom was happy, dad was very happy and pretty sure her car was happy. Months later after the miracle dad went into the trunk for some reason unknown. The plastic around the little trunk lamp was all discolored brown. The trunk light was operated by a tilt switch which apparently failed closed. Eventually the bulb burned out and the problem went away. Go figure? :) Rough guess maybe 30+ years ago.

Ron
 

tomb275

Joined Oct 31, 2022
3
1. There is a 5 year rule of thumb for (non BEV) vehicles: replace when 5 years old, they might go longer, but not much. (Always on trickle charger when parked last much longer.)

2. With modern vehicles some time out and go to sleep after 15 minutes being off (varies) to reduce parked draw. If vehicle doesn’t enter sleep mode and parked long could excessively deplete battery.
 

MrSalts

Joined Apr 2, 2020
2,617
1. There is a 5 year rule of thumb for (non BEV) vehicles: replace when 5 years old, they might go longer, but not much. (Always on trickle charger when parked last much longer.)

2. With modern vehicles some time out and go to sleep after 15 minutes being off (varies) to reduce parked draw. If vehicle doesn’t enter sleep mode and parked long could excessively deplete battery.
Define "sleep mode" current draw. I'd say it should be 100 microamps or less. The cars I've monitored seem to be at 5 to 15 milliamperes but, some cars just don't get that low as they briefly keep checking (and finding) a key fob within a 5 meters or so and they just stay in the awake mode and continue to draw 50 to 150mA and the battery dies after a week or so. Some brands are worse than others - typically a purchased module so "brand" is a bit broad. Models or platforms should be more correct as the Honda CR-V and Accura RDX share nearly every part so they have the same keyless entry mechanism. It works ok. The Accord, on the other hand, with the Remote Start feature, just doesn't want to turn down to sleep mode).
 
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