Car battery draining when parked

[StottyEvo]

If I leave my car over the weekend without starting the battery will be flat and I'll have to jump start it. I've replaced the battery and the problem persists.

I left it about 40 hours a few days ago, and the battery had drained to the extent that the interior light wouldn't turn on. Is their an easy way to troubleshoot the problem and find out what is draining the power? I have a feeling that the aftermarket tracker that was installed is the culprit.

[TooMany2cvs]

Time to get the multimeter out and start tracking down what drain there is and where.

[996TT02]

Ammeter between one battery terminal and it's lead, then remove fuses until the current draw stops.

[Hol]

I had this and it needed a proper mobile sparky to come out with his meters to identify the drain.

Mine was a window closure unit that was constantly trying to close the windows.


You can hook up a multimeter to the battery and keep pulling fuses, until you locate the correct curcuit but a sparky will find it in 1-2 hours.

[Spare tyre]

quick ones would be radio / cd changer playing up
glove box light
boot light
footwell light
interior light

[ging84]

ordinary multi meter won't really help, you need a clamp meter so you can monitor the current drain, then pull out fuses till you find which ones stops the drain

[trickywoo]

StottyEvo said:

Is their an easy way to troubleshoot the problem and find out what is draining the power? I have a feeling that the aftermarket tracker that was installed is the culprit.

http://www.wikihow.com/Find-a-Parasitic-Battery-Drain

Thats the standard procedure but if you think its the tracker you need to find the power feed and fuse for it as its not likely to be wired into the main existing car circuit via a fuse box.

[TooMany2cvs]

ging84 said:

ordinary multi meter won't really help, you need a clamp meter so you can monitor the current drain, then pull out fuses till you find which ones stops the drain

You don't need a clamp meter. Just remove the battery -ve, and put the meter probes between cable and terminal. You might need to wait until various things (stereo, ECUs) have re-initialised, and you'll probably need to shut the alarm up. That'll give you the complete draw.

Then pull all the fuses, and see if there's anything left. Then put the fuses in one-by-one (or just check across each fuse's terminals, if the fusebox gives good enough access)

[Krikkit]

TooMany2cvs said:

ging84 said:

ordinary multi meter won't really help, you need a clamp meter so you can monitor the current drain, then pull out fuses till you find which ones stops the drain

You don't need a clamp meter. Just remove the battery -ve, and put the meter probes between cable and terminal. You might need to wait until various things (stereo, ECUs) have re-initialised, and you'll probably need to shut the alarm up. That'll give you the complete draw.

Then pull all the fuses, and see if there's anything left. Then put the fuses in one-by-one (or just check across each fuse's terminals, if the fusebox gives good enough access)

Just don't try and start it like this!

[Superhoop]

TooMany2cvs said:

ging84 said:

ordinary multi meter won't really help, you need a clamp meter so you can monitor the current drain, then pull out fuses till you find which ones stops the drain

You don't need a clamp meter. Just remove the battery -ve, and put the meter probes between cable and terminal. You might need to wait until various things (stereo, ECUs) have re-initialised, and you'll probably need to shut the alarm up. That'll give you the complete draw.

Then pull all the fuses, and see if there's anything left. Then put the fuses in one-by-one (or just check across each fuse's terminals, if the fusebox gives good enough access)

This ^^^

But I would also recommend locking the vehicle, as a lot of cars now don't fully shut down until locked

[StottyEvo]

Superhoop said:

TooMany2cvs said:

ging84 said:

ordinary multi meter won't really help, you need a clamp meter so you can monitor the current drain, then pull out fuses till you find which ones stops the drain

You don't need a clamp meter. Just remove the battery -ve, and put the meter probes between cable and terminal. You might need to wait until various things (stereo, ECUs) have re-initialised, and you'll probably need to shut the alarm up. That'll give you the complete draw.

Then pull all the fuses, and see if there's anything left. Then put the fuses in one-by-one (or just check across each fuse's terminals, if the fusebox gives good enough access)

This ^^^

But I would also recommend locking the vehicle, as a lot of cars now don't fully shut down until locked

Brilliant information, thank you very much. I'll do this Saturday morning when I have a vault meter. I'll let you know how I get on.

[StottyEvo]

trickywoo said:

http://www.wikihow.com/Find-a-Parasitic-Battery-Dr...

Thats the standard procedure but if you think its the tracker you need to find the power feed and fuse for it as its not likely to be wired into the main existing car circuit via a fuse box.

I followed these steps, the drain was at a consistent 40milliamps. I pulled all the fuses in the fusebox under the bonnet and nothing changed. I then opened the door to do the interior fuse box and found that the drain dropped to 11milliamps!

I then pulled all but 7 of the fuses in the internal fuse box and nothing changed. (the last 7 were very hard to get out)

Any idea's why opening my door would stop the drain?!

[kambites]

Perhaps something to do with the alarm? Does the drain drop if you open the other door, too?

Something doesn't add up anyway. I think most car batteries are about 50Ah. At a drain rate of 40mA, your battery should last over a month. For your battery to drain in 40 hours, something is drawing about an Amp. Have you checked the draw with the alarm and immobiliser activate?

Edited by kambites on Friday 3rd October 14:35

[vtecyo]

If you've got an aftermarket alarm / immobiliser and you don't know who fitted it, it'll be that.

[littleredrooster]

If it's genuinely only taking 40 mA, it suggests that the battery has just died of old age and isn't related to the current leakage. Most OE alarms take 10 40mA without draining the battery in a couple of days.

Many newish cars use the drivers door switch to trigger the fuel pump priming circuit; why this should lower the current drain is a mystery.

[StottyEvo]

In a separate test I recorded the voltage through the battery at 12.65v, after 27minutes it was at 12.5v so a drain of 0.3v per hour roughly.

I'm starting to think I'm looking at the wrong scale on the multimeter, maybe its 400milliamps drain and not 40.

The battery is brand new, it was the first thing I changed with the battery drain issues. The alternator also seems to be functioning fine as the amps just as expected when the engine is running.

[croyde]

Just chipping in as I have the same problem. Haven't found a likely culprit by testing all the fuses. Bloody annoying but ok if I use the car at least every 3 days.

[kambites]

You definitely need to check whether there's a difference in the drain current when the alarm is armed and disarmed.

[J4CKO]

My solution was to buy a different car

I did the Multimeter thing to work out where the Amps were going, saw the technique on a documentary , it told me I had to turn loads of stuff off and make something called and "Air Scrubber" from a box and Duct tape which didn't help.

[StottyEvo]

kambites said:

You definitely need to check whether there's a difference in the drain current when the alarm is armed and disarmed.

Sorry I forgot to mention I did this test, the drain was displaying 0.4 on the multimeter, I locked the car it spiked to 1.55 then dropped back down to 0.4 pretty quickly. Locking or unlocking the car doesn't make a difference, the only thing that brings the drain down is opening any of the doors (boot included)

I've done a bit of googling but can't find anything about opening doors stopping the drain!