Parasitic battery draw

[SA1]

Dear All,

I have recently changed my battery after leaving the car (w211 e320 2006) stood for 10 days. I thought it was suspicious as no power was inadvertently left on and the battery drained to about 10-11V. I had a spare battery which I used for a while and then bought a 019 AGM battery (stop/start) - my car is not stop start (previous was normal 019 AGM) but they assured me it would be OK.

I tested for parasitic draw (disconnected neg terminal and connected multimeter to that and neg post on the battery) and with everything turned off I got a reading of 300mA (so quite a bit above the max of 50mA). In order to make sure everything was off I opened the doors and then locked the passenger and rear door by pressing the push knobs down. I used a g clamp for the driver door to make the lights go out (to allow access to fuses), and clicked the boot lock so that I could access the fuses there with the boot open. I waited for 60 mins for car to go to sleep mode (my car has SBC which carries out self tests so waited full sleep time - also disconnected neg lead of auxiliary battery).

I pulled all the fuses in the boot (and relays) and in the front driver side and saw no change in the draw. I also tested the ones under the hood and still the same (I didn't see any hood switch - am I mistaken?)
I have no faults come up on the driver screen. I attached my OBD and had fault code for resistance of ignition circuit with component r12/13 (as well as r12/14) driver airbag squib 1 (and squib 2) too high; but as stated no fault in car icons.

My car should be Ok if I keep driving it to maintain the charge but I am concerned that if I leave it not driven for a period then I will start getting problems with the new battery so I would like to find out what is causing the draw sooner rather than later. Any comments or suggestions would be appreciated, thanks.

 

[LostKiwi]

Do you have the factory CD changer?
The CD changer on my 230 wouldn't go to sleep and was the cause of my parasitic drain.

 

[SA1]

Do you have the factory CD changer?
The CD changer on my 230 wouldn't go to sleep and was the cause of my parasitic drain.

Yes I do have the factory radio/cd/navigation, but when I carried out the draw test and removed the 7.5A fuse 3 in the boot, the draw remained the same.
How did you test and find out the drain was from the CD changer?

 

[LostKiwi]

I found it by accident. I was sitting in the car and heard it clicking when everything was turned off.
Try disconnecting it from power and seeing if the battery drains.

 

[Simon22]

had battery drain on my ML turned out to be axillary battery which was knackered and was draining the main battery, my W211 battery drain was the electric seats modules which i disconnected both sides, problem sorted, hope this helps.

 

[SA1]

I found it by accident. I was sitting in the car and heard it clicking when everything was turned off.
Try disconnecting it from power and seeing if the battery drains.

Thanks. I would have thought taking out the fuses (f26 and f28 for the cd changer and radio respectively) according to my manual should break the circuits to corresponding circuits so I thought that would mean I would be effectively disconnecting power to those circuits? I am not sure how else to disconnect it from the circuit, unless I remove the CD connecting plugs at the back of the CD. My other thought is to start looking at the front and back pre fuse boxes and consider removing some of these connection fuses as I haven't tried that yet.

 

[SA1]

had battery drain on my ML turned out to be axillary battery which was knackered and was draining the main battery, my W211 battery drain was the electric seats modules which i disconnected both sides, problem sorted, hope this helps.

My auxiliary battery is 12v and ok, but I could start disconnecting modules. I have only been pulling out fuses and relays and watching for current drop as I thought this was the usual procedure, but maybe I should see what effect disconnecting various connections does as well.

 

[Tony Dyson]

My auxiliary battery is 12v and ok, but I could start disconnecting modules. I have only been pulling out fuses and relays and watching for current drop as I thought this was the usual procedure, but maybe I should see what effect disconnecting various connections does as well.

Pulling fuses will work providing you leave the fuse pulled out until you've found the drain, replacing the fuse pulled as you progress will potentially 'wake up' that particular and associated circuits complicating the readings. Further reading fluctuations will manifest when those previously woken modules return to sleep.
An alternative method is to non-invasively read the PD in mV across each fuse and using the cheat sheets herewith find the estimated circuit current.

 

[clarkmichigan55b]

After checking everything else it could be your alternator. Check this out.

 

[SA1]

After checking everything else it could be your alternator. Check this out.

Thanks for the video. I changed the alternator in 2018, and I think it's still OK. The readings I got today (with engine on) were, first few minutes 14.08V ; with headlights/fan/radio 13.97V; with fan only 14.04V. I switched from DC to AC and voltage was zero, which I believe is an indication of no flow of voltage back and forth, so diode rectifier OK. When I switched off the engine the voltage stabilized at about 12.55V.

 

[SA1]

Pulling fuses will work providing you leave the fuse pulled out until you've found the drain, replacing the fuse pulled as you progress will potentially 'wake up' that particular and associated circuits complicating the readings. Further reading fluctuations will manifest when those previously woken modules return to sleep.
An alternative method is to non-invasively read the PD in mV across each fuse and using the cheat sheets herewith find the estimated circuit current.

Thanks for the info Tony and the attachments. I have been replacing fuses each time, but I think I'll try your method. I tried measuring PD across each fuse. I am thinking about getting a better multimeter (maybe for around £50) as mine doesn't measure mV (just V) and I noticed that the current reading only seems to read in the Amp setting and not the mA which gives me 0.3A. I would have thought that 300mA would register when I switch to my mA scale, but just came up with overload. I'll try again when I get my new meter.

 

[Tony Dyson]

Thanks for the info Tony and the attachments. I have been replacing fuses each time, but I think I'll try your method. I tried measuring PD across each fuse. I am thinking about getting a better multimeter (maybe for around £50) as mine doesn't measure mV (just V) and I noticed that the current reading only seems to read in the Amp setting and not the mA which gives me 0.3A. I would have thought that 300mA would register when I switch to my mA scale, but just came up with overload. I'll try again when I get my new meter.

You're welcome, cheap multimeters can serve a purpose but a good quality autoranging, high count display, low resolution, true RMS instrument is needed for this level of faultfinding. Good luck in finding it!

 

[SA1]

You're welcome, cheap multimeters can serve a purpose but a good quality autoranging, high count display, low resolution, true RMS instrument is needed for this level of faultfinding. Good luck in finding it!

Can you or anyone else recommend a good multimeter? - I have seen Fluke, but they are generally a bit more than I wanted to pay.

 

[Blobcat]

Can you or anyone else recommend a good multimeter? - I have seen Fluke, but they are generally a bit more than I wanted to pay.

Fluke is good (I’ve a few…) screw fix have some cheap and cheerful ones

 

[Tony Dyson]

Can you or anyone else recommend a good multimeter? - I have seen Fluke, but they are generally a bit more than I wanted to pay.

Would it be for dedicated automobile use or are you looking for a general all rounder to test AC circuits as well?
Any other specific needs, Clamp Meter, Temp Probe, Capacitor, Diode Check etc?
Proprietary manufacturer or Chinese?
What is your budget?

 

[SA1]

I don't think I can run to the price of a Fluke, but a bit more expensive than a cheap unit. I was thinking around the £60 mark.
Mainly for the car. Not sure how useful a clamp meter will be for me, mainly want it for resistance, mV, V (AC/DC), low/high current, accuracy relevant to cars.
Manufacturer doesn't matter to me.

 

[Tony Dyson]

I don't think I can run to the price of a Fluke, but a bit more expensive than a cheap unit. I was thinking around the £60 mark.
Mainly for the car. Not sure how useful a clamp meter will be for me, mainly want it for resistance, mV, V (AC/DC), low/high current, accuracy relevant to cars.
Manufacturer doesn't matter to me.

10A is a pretty standard limit on current measurement through a multimeter and great care should be exercised not to make available anything potentially greater

https://www.enrgtech.co.uk/product/multimeters/ET14143141/HEX60-D

So this Amprobe BEHA one is the most cost effective multimeter I can find with the min specifications I would look for in a quality instrument.

https://www.wavetek.com/collections/multimeter/products/wavetek-39xr

An alternative is the Wavetek 39XR which again ticks all the boxes but doesn’t claim resolution capabilities which I have requested, it’s also autoranging which is a benefit, Wavetec used to be available off-the-shelf in the UK but the website reads that there may be shipping and import charges from the US involved now, something that needs confirming if you’re interested. Good luck!

 

[SA1]

10A is a pretty standard limit on current measurement through a multimeter and great care should be exercised not to make available anything potentially greater

https://www.enrgtech.co.uk/product/multimeters/ET14143141/HEX60-D

So this Amprobe BEHA one is the most cost effective multimeter I can find with the min specifications I would look for in a quality instrument.

https://www.wavetek.com/collections/multimeter/products/wavetek-39xr

An alternative is the Wavetek 39XR which again ticks all the boxes but doesn’t claim resolution capabilities which I have requested, it’s also autoranging which is a benefit, Wavetec used to be available off-the-shelf in the UK but the website reads that there may be shipping and import charges from the US involved now, something that needs confirming if you’re interested. Good luck!

Two good choices Tony. Have you or anyone else have cause to use a digital clamp - I might consider getting one if it makes the process a bit easier?

 

[Tony Dyson]

Two good choices Tony. Have you or anyone else have cause to use a digital clamp - I might consider getting one if it makes the process a bit easier?

They are an essential item if you find yourself troubleshooting electrical problems often enough, the Wavetek Meterman 210 E has an impressive spec for just over £50! Budget AC/DC Clamps are few and far between.

 

[LostKiwi]

I have several meters including one with a AC/DC clamp. The clamp does make life a lot easier for measuring current flow.

Beware not all clamp meters can read DC current.