Battery Draining

Page may contain affiliate links. Please see terms for details.

Hawkwind

Active Member
Joined
Oct 2, 2013
Messages
491
Location
Brighton
Car
CLK 320
Hi there guys,

The battery on my car (CLK320 W208), is getting drained after 5/6 days parked up unused. It jump starts and charges up fine, so I doubt I have an alternator problem, on tick over the battery reads about 13.98V, once fully charged the battery reads 12.27V.

Today I attached my multi-meter and pulled all of the fuses in turn to see if I could discover what if anything is drawing power from the battery. I opened the boot and switched off the boot light, I then opened the drivers door and switched off the interior lights and opened the bonnet.

I then left the car for about ten minutes and took a battery reading which was 12.26V - 12.27V (it was oscillating between the two). I have now pulled every fuse that I can find (boot, drivers side dash and engine bay) and there was no fuse that I could find causing a voltage drain on the battery. However during this process which took me maybe 15 minutes, the voltage of the battery dropped from 12.27V to 12.25V.

As an afterthought, I have also disconnected the battery earth and the reading is now 12.23V, but 12.22V with the earth lead reconnected (probably should have done this first). So this suggests to me that there is a drain of 0.01V, if this is significant :dk:

The battery was already installed when I bought the car and the dealer said it was a new battery. The makers name on the battery is Forenbuhl, which I have never heard of and is possibly the crappiest/cheapest battery the dealer could find :dk:
 
I'd take the battery to a specialist and have it load tested to see if its holding its charge if you are unsure of its quality. You may not have a drain at all and just a battery beginning to fail.
 
You need to test the battery and check the current drain in Amps.
 
The voltage readings indicate a substantially discharged battery perhaps only 25% -33% charged. it's hard to be specific because it depends on the exact battery chemistry but as a minimum a fully charged battery should read 12.6 volts with no load and after a period of rest. If you measure the voltage immediately after charging the voltage will be higher and invalid due to the surface charge effect.

I agree you need to get the battery tested although it will need to be fully charged first. My guess is there is something wrong. It may be there is no significant drain and the battery is simply failing.

To give figures for my battery an original MB silver calcium wet cell; after a full charge and 24 hours rest it reads 12.8 volts. An AGM battery might be a couple of tenths higher and a bog standard cheap wet cell as low as 12.6 volts.
 
Last edited:
Thanks for the replies guys.

Any suggestions who would be able to check the battery, or can any garage do it?
 
Any battery specialist or a Bosch service dept' would be my choice.
 
go to kwikfit, they will test it for free
 
And condemn it .....
 
I had batteries checked for free at Halfords shops (in shops where they have a car electrician onsite).

As for 'condemning it'... the test is very simple and you can see the gauge for yourself while the battery is being tested.

At the time they would also fit the battery for you, either for a fiver or for free (depending on the 'offer' they had going).


Or you could buy the battery tester and test it yourself....
 
Just to throw in my 0.02 on battery testing.
Typically falls into one of two categories (after checking with a multimeter) :
HRD, high rate discharge testers, these simulate a load and last for around 10 seconds, this should be done at 50% of the CCA rating. So an 800CCA battery should have a load of 400A for 10 seconds. The problem is, most garages using these HRD testers are smaller fixed amp types of 100/125A.

Digital Conductance Testers, the more popular and more modern test method, the user types in the CCA and the tester measures the resistance across the plates and gives a suggested CCA result compared to the voltage. Giving a pass/fail result.

(I was going to leave out Hydrometer testing as the majority of traditional wet batteries now have sealed lids, but for older style batteries, they are my preferred tester type when used alongside a HRD tester)

Though I am no longer directly involved in the battery industry, when testing a potential faulty battery, the digital tester was first, followed by HRD (if required) and Hydrometer if possible.
 
Last edited:
OK so I have taken the car down to Halfords and had the battery tested and it tested good on their Yuasa battery tester thingy.

I was kinda hoping it would be a dodgy battery because that would be a quick fix, bit it looks as though I'm in for the long haul.:(

As you all may have guessed electickery isn't my strong point, so if you guys could talk to me like I'm a complete idiot, I might have a chance of understanding :D

BlackC55 said I have to check the current drain in amps :dk:

OK so I have my multi-meter, where do I go from here?
 
I've had a look on youtube and I thought I had a good idea how to do this, but now I'm not so sure, I've included a couple of pictures, maybe you can tell me if I have the multi-meter hooked up and set correctly?





I seem to be getting a lot of variable readings. When I first connected the meter, I was getting about 0.48 this gradually went down to 0.12/0.11 but it doesn't seem to have anything to do with the fuses I pull, occasionally it'll jump back up to 0.48.

I'm a bit puzzled, have I got the leads from the meter plugged in correctly?
 
As far as I can tell from the pic you have removed the battery negative lead and put the meter in series which is correct for measuring current. Can't see clearly what range the meter is on but it's wise to start high and turn the meter down to the correct sensitivity. If the 0.12 reading is amps which is 120mA then that is too high. It should fall to something in the region of 50mA or 0.05 A when fully asleep.
 
BTW you have the polarity of the meter leads wrong but it doesn't really matter and won't affect the reading other than to display a minus sign.
 
Thanks for the reply 190.

I have the selector switch turned to 10 (whatever that is, didn't want to destroy the meter).

I'll experiment with the settings, but mainly wanted to know that I had the leads plugged into the meter correctly. The red lead is plugged into the 10A Max socket, which I presume is correct?

Yes I have the meter in series with the battery :thumb:

What do you think was causing the variation in readings? I had left the car open, with everything turned off for at least 15 minutes before removing the battery earth terminal, would that 'wake up' the car again?

Thanks again for your help.
 
The car should be in the same position as when parked, ie locked with alarm (if fitted) and immobiliser activated.

So you'll need to connect the ampmeter in series then lock the car apart from the bonnet. If you have a bonnet alarm switch, press it down manually (make sure the emergency key is working beforehand...).

This is to replicate what happens when the car is parked up overnight.

Then read the current draw in amps... the next step is removing the relevant fuses one at a time trying to work out which circuit is causing the excessive current draw.
 
Thanks Mark, I'll follow your instructions tomorrow.

I have been trying to do this with the drivers door open, because of the fuses in the dash side panel. These fuses I think are all for lights, so is it safe to assume that these will not cause the battery to drain?

So, just so I understand correctly, I need to release the bonnet, then lock the car with the remote, wait for the car to 'go to sleep' and then open the boot with the emergency key?(not the remote boot release).

Also how long before the car 'goes to sleep'?

Sorry for all the questions.
 
Hawkwind, you can start by testing with the car unlocked, as this is easier to do, though be aware that in this way you will not be testing for any excessive current draw by the immobiliser or alarm (if fitted).

If you are lucky to find high current draw and isolate the issue, then no need for testing with the car locked (and alarmed).

However, to test the car locked, you will need to open the boot, connect the tester (I understand that your battery in in the boot) , then hold down the boot sensor (if you have one) so that the alarm thinks the boot is closed (and the boot light is off), lock the car and then see what reading you get. I believe the car alarms within 15 seconds, there should be a flashing led on the dash once alarmed.
 
OK so some progress, I hope!

Followed your instructions Mark and once again checked every single fuse, even checked the ones hidden under the AC service panel and not one bloody fuse made the slightest difference.:mad:

Now when I started yesterday, the first thing I checked was the radio/CD player, it's the only non OEM part on the car, so it was the first thing I suspected and checked. When I checked it yesterday, I don't think the car had gone fully 'sleepy byes', so I was getting some odd readings, so I obviously hadn't checked it properly.

As it was the last thing I checked today I noticed that it did make a difference. The reading dropped from from 0.11 to 0.02, which a think might correspond to 110mA and 20mA.

So now I have completely removed the radio, no ICE, but I hope a car that will start! Which after all is the primary purpose of having a car :D

I will monitor the battery voltage and see if there is a drop in charge over the next 24hrs.

Just one more question guys, the radio is a 'Beat285', which doesn't seem to have a brand name. Could it be the radio itself that is causing the battery drain, or is it more likely the way it has been wired into the cars electrics?
 

Users who are viewing this thread

Back
Top Bottom