Battery drain

[recoil]

Hi, my C240 Auto runs fine if use every day or so.

If I leave it parked for say 2 weeks, the battery will be dead, I've taken it in to MB they said they could not see any drain on it but replaced the battery anyway, £250 down the drain.

Took it on holiday driven every day so all was fine, parked up again left it for 2 weeks battery dead, now Im getting p11sed off, MB said it was fine.

Took it back to MB they had it for a week now, now they are saying the car stereo is draining the battery (why they didnt see that before I dont know), and also the rear window regulators are draining (the windows work fine).

Now my question could these three things be draining the battery enouth to flatten the battery.

I dont understand how a window regulator can drain power?? Are they trying to pull a fast one??

 

[MIW615]

Hi, my C240 Auto runs fine if use every day or so.

If I leave it parked for say 2 weeks, the battery will be dead, I've taken it in to MB they said they could not see any drain on it but replaced the battery anyway, £250 down the drain.

Took it on holiday driven every day so all was fine, parked up again left it for 2 weeks battery dead, now Im getting p11sed off, MB said it was fine.

Took it back to MB they had it for a week now, now they are saying the car stereo is draining the battery (why they didnt see that before I dont know), and also the rear window regulators are draining (the windows work fine).

Now my question could these three things be draining the battery enouth to flatten the battery.

I dont understand how a window regulator can drain power?? Are they trying to pull a fast one??

The test is quite simple, buy using a multimeter they can measure the "drain" in m/a. Then buy removing fuses one at a time they can pinpoint the offending components. The stereo drain should be very low as with everything turned off it's only the memory that is draining - not sure about the regulators, seems strange, I'm sure someone here will be able to advise.

How much "drain" is there?

I would be inclined to take the car to a reputable auto-elctrician for proper diagnosis

 

[recoil]

The drain will flatten the battery in 2 weeks, to the point where I have to use a key to open the door, so central locking wont work either, untill I use jump leads from one of my other cars

 

[MIW615]

The drain will flatten the battery in 2 weeks, to the point where I have to use a key to open the door, so central locking wont work either, untill I use jump leads from one of my other cars

Sorry, I didn't make myself clear - when MB measured the "drain" they would have had a figure in m/a (milli-amps) ask thenm what the figure is.

Also I would check that the alternator is charging - takes 2 minutes with a volt meter - did MB check this and if so what were the voltage readings?

 

[recoil]

Well MB have just phoned again, they say that the rear-right window regulator is not working, and the car stereo so I told the just disconect the fuse the stereo, un plug regulator, gonna go pick car up in a bit.

I'll ask them the figures there.

But also what I'll do is leave the car for another 2 weeks and see what happens

Thx for you relpy thou

 

[MIW615]

Also I would check that the alternator is charging - takes 2 minutes with a volt meter - did MB check this and if so what were the voltage readings?

If the alternater is good then I would expect a voltage of somewhere between 13.5 - 13.8 volts

Any less than that the battery will go flat - any more the battery will cook

 

[jberks]

Can I barge in on this one.

We have a similar issue on our E220cdi (2003).
Wouldn't start one morning though it had been fine the night before. Put a new battery in (£50 & 10 mins - what did they do for £250??). .Since then, we've had several occasions where, immediatey after start up, we get the "Consumer circuits off" warning on the dash. Everything seems to work fine so if the warning was true, it was only true for a second or so.
With the engine off, we are seeling a shade over 12v. With the engine on, 13.5-13.8 roughly.
The only thing we have been able to find is that the boot release handle sticks (its electric on the 211) and was possibly stuck in the open position.
Could this do it?

We intend to look at the drain rate. Anyone know what it should be on a non command equipped 211?
Also, how do I check this? I assume I remove the earth strap and put my meter in line, but presumably I will then be running the car through the meter so is a small digital meter up to the job or will I blow it?

 

[wireman]

With the engine stopped and all electrical loads switched off measure the battery current,

Key out off ignition and interior light switched to off.

Lift off the ground/earth strap and connect your ammeter in line.
Always set an ammeter to its least sensitive range (highest amps) on first connection, reduce the range as you require to get a better ("bigger") reading, say start at 1A (or 10A) and work down the ranges to get a worth while indication.

DO NOT SWITCH ANY LOADS ON WITH THE METER ON A SENSITIVE SETTING, IT WILL MELT.

If you find a drain current much more than 100mA (1/10A) there is a chance that your battery will go flat after a week or two, isolating each circuit in turn by fuse pulling will identify which circuit is responsible for the excessive drain.

At 100mA a 50Ah battery (fully charged) should last for more than 500 hours (~2 1/2 weeks) perhaps even 700 - 100 hours.

If you are only using the car occasionaly fit a mains powered charger and use it whilst the car is stored.

About the voltage of a car battery, 10.8 volts is the voltage below which the battery must never be discharged, a reduced life will result from using a battery in this very low state of charge.
13.5 - 13.8 volts is the voltage at which a battery is float charged, it can stand this for ever and will not be damaged. However the rate at which the battery is charged at this voltage is low, it will take forever to fully charge the battery.
14.1 - 15 volts is the voltage at which a flat battery should be recharged for about 24 hours, any longer may dry out the cells as a result of gassing.
The alternator is voltage regulated and should for most normal vehicle aplications produce 14.1 - 14.4 volts at the battery when running and on load, any less and the battery will be under charged permanently (and die prematurely).
The alternator is not the best charger for a battery in a low state of charge, if you get a flat battery it realy should be charged of an external charger to get it into the best of health. To fully recharge a discharged battery on the vehicle would take days of continuous running.

 

[jberks]

thanks wireman.

 

[television]

The other thing is that the circuit must not be broken when joining up the meter if it is broken the leak path can be lost and your readings will be of no use.


So you need 2 leads on one terminal on the meter.

Attach the one lead with crocodile clip to the battery lead.

take one of the double leads with the probe and hold this down hard to the center post on the battery slide the battery clamp up the probe and attach the other meter lead with the crocodile clip onto the battery post.

Do have the meter set to Max amps before you start

 

[Ellsy Tanners]

Be very carefull when doing the test, many things will blow the fuse in the mutimeter. dont turn anything on and dont turn on the ignition or this will blow the fuse. Most multi meters only have a small fuse which will blow very easily about 10amp.

 

[recoil]

Car is back from MB now, minus a radio and off side window regulator.

The bloke told me the normal drain on a battery should be about 0.02 amps, the drain on mine was 0.5 amps

 

[MIW615]

Car is back from MB now, minus a radio and off side window regulator.

The bloke told me the normal drain on a battery should be about 0.02 amps, the drain on mine was 0.5 amps

If you were "draining" 0.5 amps then you had / have a problem, you need to establish which of the two components are causing the drain the most.

I measured the drain on my W210 a few weeks ago and it was 35m/a or 0.035amps, so I would expect yours to be similar if the radio is okay and just drawing enough current for it's memory. Sounds like your main problem is the window motor

 

[recoil]

I will its all disconected now, so I just want to wait a while and see if that is the problem I will then conect one thing at a time, and work out what needs to be replaced. MB said the regulator I dont know much about cars, is that the motor?? sorry if thats a stupid question, also gonna get me a decent multimeter today, another stupid question here, how do you measure the 'drain'

 

[MIW615]

how do you measure the 'drain'

Read "wireman's" reply on the first page of this thread

 

[television]

I will its all disconected now, so I just want to wait a while and see if that is the problem I will then conect one thing at a time, and work out what needs to be replaced. MB said the regulator I dont know much about cars, is that the motor?? sorry if thats a stupid question, also gonna get me a decent multimeter today, another stupid question here, how do you measure the 'drain'

You are working backwards as once disconnected the path of the drain may not show up.

In post 10 the way to connect up is there, you just put the ammeter on the MAX highest range AMPs and turn the meter range down till you get to milli amps and a range that gives you a sensible reading

Most meters have a 200m/a range and that will be the lowest setting that will be useable

 

[MIW615]

MB said the regulator I dont know much about cars, is that the motor??

The regulator has the motor attached, yours may be something like number 8 in picture.........................

 

[television]

Most window mechanisms only work with the door open or Key1 and 2, if it is that could it not be the simple switch on the door that is leaving it active