Measuring electrical current draw 12V DC.

[aguycalledsteve]

I'm having a bit of an issue with my Disco when i leave it parked up for a few days, I'll come to it and it'll have a flat battery. I understand that the best method to find out what is causing it to go flat is to put a multimeter between one of the battery connectors and the battery to then remove fuses one at a time and see when it drops to zero.

I have a multimeter like this one :

Could anyone tell me which of the round ports I use for the red probe? Also where do i turn the dial to, to best measure the draw for 12V?

 

[bigegg]

You might be better off measuring the voltage across the fuse terminals (after removing the fuse).
If a voltage shows (turn the dial to "20") then thats your circuit.
Use the right hand for the red, black goes to center.

You could also use the same points to measure the current. (Again, remove fuse)
Left hand connection for the red, and dial set to 10A.
If that doesnt show anything, swap red to the right hand connection, and move dial anticlockwise one click to 200m

 

[TechWise]

You put your black probe in the COM port as always. You put the red probe in the one marked 10Adc, assuming you want to measure a fairly large current up to 10A. Rotate the dial to point at 10A at around the 4 o-clock position. You see up at the top right where it says A then a bar with dots under it? That's the symbol for DC. You'll see above that is says V~. That squiggle is the symbol for AC.

I see it says "unfused" so be very careful. You could destroy your meter very easily if you pull more than 10A. I would suggest putting a 10A fuse in series just in case.

 

[voipio]

A DC current clamp meter makes the job easier.

Something like the UNI-T UT210E won't break the bank, and can resolve down to 1mA, though it needs careful zeroing before measuring such small currents, as the earth's magnetic field can introduce errors.

https://www.amazon.co.uk/UT210E-Current-Meters-Capacitance-Tester/dp/B00O1Q2HOQ

 

[Morrisman]

You’d need quite a big current draw to flatten the battery totally in a couple of days, almost like leaving the side lights or fog lights on.

 

[Alan Reynolds]

These cheap meters are ok, I use two of them all the time. BUT when measuring current on the 10 amp range you should be careful as being unfused, iy blows the printed circuit board copper track instead. You can rpair it and put a 10 amp fuse in at the same time. My van has always killed its battery after a couple of weeks because it runs an immobiliser, radio, and two trakkers. I use a solar cell that keeps up in the summer months but struggles in the dark winter months. It could be something like a cubby light or boot light that s on.

 

[sako243]

BUT when measuring current on the 10 amp range you should be careful as being unfused, iy blows the printed circuit board copper track instead.

Just put an external fuse inline with it.

 

[RonA]

If it’s taking days to discharge, would have thought the smaller milliamperes ranges would be more applicable.
RonA

 

[Ruffian]

Battery drain usually will be down at 0.03amp.

Usually discovery will be cd player in the boot staying live or stereo not shutting down properly.

You will have some residual drain due to alarm etc.

 

[bricol]

You’d need quite a big current draw to flatten the battery totally in a couple of days, almost like leaving the side lights or fog lights on.

A relay coil energised will drain a decent new car battery in a few days to point you get a "CLICK" on turning the key . . . took me a while to track that one down

 

[aguycalledsteve]

You might be better off measuring the voltage across the fuse terminals (after removing the fuse).
If a voltage shows (turn the dial to "20") then that's your circuit.
Use the right hand for the red, black goes to center.

You could also use the same points to measure the current. (Again, remove fuse)
Left hand connection for the red, and dial set to 10A.
If that doesn't show anything, swap red to the right hand connection, and move dial anticlockwise one click to 200m

Actually that might be a better way of doing it. It would be more accurate that just looking at the draw happening at the terminal as that would include and alarm and immobiliser current as well as the circuit that's problematic. Thanks

You put your black probe in the COM port as always. You put the red probe in the one marked 10Adc, assuming you want to measure a fairly large current up to 10A. Rotate the dial to point at 10A at around the 4 o-clock position. You see up at the top right where it says A then a bar with dots under it? That's the symbol for DC. You'll see above that is says V~. That squiggle is the symbol for AC.

I see it says "unfused" so be very careful. You could destroy your meter very easily if you pull more than 10A. I would suggest putting a 10A fuse in series just in case.

Thanks, I rarely use my multimeter for anything other than checking voltage of DC batteries on my vehicles. Just want to make sure that I'm doing it right.

A DC current clamp meter makes the job easier.

Something like the UNI-T UT210E won't break the bank, and can resolve down to 1mA, though it needs careful zeroing before measuring such small currents, as the earth's magnetic field can introduce errors.

https://www.amazon.co.uk/UT210E-Current-Meters-Capacitance-Tester/dp/B00O1Q2HOQ

I'll add this to my xmas list. looks a handy bit of kit that. I'm trying to get to the bottom of my flat battery using the kit I already have

You’d need quite a big current draw to flatten the battery totally in a couple of days, almost like leaving the side lights or fog lights on.

There's definitely no lights being left on. Especially interior lights. I know i can leave the truck for a couple of days and it will start but any longer and when i come to start it, it will just turn over once as if flat? Put the battery on charge and it will start no problem.

These cheap meters are ok, I use two of them all the time. BUT when measuring current on the 10 amp range you should be careful as being unfused, iy blows the printed circuit board copper track instead. You can rpair it and put a 10 amp fuse in at the same time. My van has always killed its battery after a couple of weeks because it runs an immobiliser, radio, and two trakkers. I use a solar cell that keeps up in the summer months but struggles in the dark winter months. It could be something like a cubby light or boot light that s on.

I'm hoping that the problem isn't 10A in draw tbh. It seems to be something that's draining the battery slowly. That's why i thought checking the draw with the fuses removed one at a time would identify the circuit that's causing the issue.

 

[bigegg]

Its *very* unlikely to be anything close to 10A, but why risk blowing your meter by using a lower range? (Initially at least).
The 10A test is to protect your meter, as much as anything.
A 10A inline fuse is probably a good idea, tbh.

 

[slim_boy_fat]

How old is the battery?

 

[aguycalledsteve]

How old is the battery?

Of an indeterminate age. Was bought as a used but known good to replace one that had dropped a cell.

 

[aguycalledsteve]

Battery drain usually will be down at 0.03amp.

Usually discovery will be cd player in the boot staying live or stereo not shutting down properly.

You will have some residual drain due to alarm etc.

I don't have such luxury as a cd changed in the boot However i did add the lightbar on the roof, so I removed the fuse for that to take it out of the equation.

I plan on locking the car with the bonnet open and with the switch down then leaving it for half hour so that everything has chance to power down properly and see what's happening in terms of draw.

A relay coil energised will drain a decent new car battery in a few days to point you get a "CLICK" on turning the key . . . took me a while to track that one down

How did you resolve that?

 

[slim_boy_fat]

Of an indeterminate age. Was bought as a used but known good to replace one that had dropped a cell.

I'd be getting it load tested, esp if you've only been shortish runs between use.

 

[aguycalledsteve]

I'd be getting it load tested, esp if you've only been shortish runs between use.

Good shout. I think I might. I've been looking at the batteries recommended for D2 TD5's and the one i have, Mine is a lot smaller. But the drain to flat still needs to be looked at I reckon.

 

[slim_boy_fat]

Good shout. I think I might. I've been looking at the batteries recommended for D2 TD5's and the one i have, Mine is a lot smaller. But the drain to flat still needs to be looked at I reckon.

Be interesting what the state of the battery when checked. If a cell is down/on the way out, I suspect that may be part of the problem, esp with Winter at the door. [But, I've been wrong before...]

 

[CompoSimmonite]

I've got one of these -
https://www.gunson.co.uk/product/77069
Uou remove the vehicle fuse,plug this device in (it's also fused) and it give a current reading

 

[aguycalledsteve]

I've got one of these -
https://www.gunson.co.uk/product/77069
Uou remove the vehicle fuse,plug this device in (it's also fused) and it give a current reading

These are cheap enough on ebay it seems. I may just invest in one. Thanks for the link