Bloody battery problems!

[John_Doe]

I haven't used the car for a few days and when I went to unlock it, it was dead. Thought maybe it was just a remote problem but car wouldn't start at all. And it was just my luck that i basically parked it in a hedge so was a bit tricky trying to jump start it with no access and not being able to move it. Anyway got it started and had a few error messages like ESP not available.

I know I will need to buy a new battery but obviously need to find the cause of the battery drain first. So out of the following what is my likely culprit

-Passenger door logo pogoing (been doing it for a while and aint noticed an issue with battery until now)
-Rear head rests did not drop after pressing the button and since being parked up last I found the problem. Was a cut tube feeding the passenger side rear seat. So reconnected and they now work. Can't see this causing an issue but its one of the things I've touched since the last time she was running fine. And a bit strange that it was just cut for no apparent reason.
-The only other thing I touched is the TV tuner in the boot. I literally took out all the boot lining to have a little browse. I didn't disconnect anything all i did was unbolt the TV tuner to get a look at the back for a part number. The reason I mention this is because when the battery first went flat I suspected the boot light was left on due to no lining (did this on my w202 before) but the light was off, although I did notice that the tv tuner was making a high pitch whine. I disconnected one of the plugs which only has two cables on it, red/yellow and brown, so guessing perm power and earth? Which obviously made it shut up.

Jumped the car and plugged it back in and drove it too work, parked for 8hours, started fine and came home. Over night the battery has gone flat again and now creating a very loud annoying ticking which is probs from the alarm having no power but its too late to care! disconnected the tv tuner again and the ticking gets louder lol. So plugged that back in. Not over keen on my neighbours but I don't really fancy someone knocking in the middle of the night asking me to shut it up!

I go on bloody holiday in 5days for two weeks so don't really fancy having it flat the whole time I'm away. Its gonna be parked in a locked garage and all that crap but still not the point lol

 

[trainer]

Hi, I had the same problem which was down to the power to my memory seats being permanently on. Try unplugging the power to the seats and see if the problem remains. If it doesn't then there is a simple fix.

 

[Alps]

just got back from 10 days away and have the same prob, dead batt!

had to use the blade key to open the boot and get a charger on it, then after an hour it started fine.

just changed the aux batt a few mnths back, and the main one had been changed 3 years ago, i`ll see how it fares over the next few mnths

 

[brigadier]

easiest way to find whats taking the power, is to check with a multimeter.
select 10amp mode. first of all you should check at negative battery terminal (take off negative terminal - join it so it goes through the meter)to see how much power in total it draws - it should be 0.0something, if it's more - take out each fuse and check across. then you can see which fuse is taking power and hopefully pinpoint the fault. some modules take power for few seconds after you connect them, so if you see something is taking power wait half a minute too see if it drops.

 

[Tinkerer]

AND if you do change your battery don't get conned into taking the cheapest choice once you have told them what car it is going on ............ my battery on an old C220D was a 100Ahr but the nice man at the garage said you don't need one that big 1) your max draw off fits a 75Ahr battery 2) it might not fit in the rack! it is foolish to believe them as the load when the car is left for a couple of weeks is enough to pull these smaller batteries down to a level where they will not start the car.

 

[panason1c]

As mentioned, the seat controllers are known to cause battery drain problems. I would try removing all non essential fuses and see if the problem goes away and then replace them one at a time.

 

[John_Doe]

Ok well I think I am getting somewhere. First chance I had to look at her was today in the rain but I'm fairly confident that I have removed enough to keep the car alive until I return from holiday lol

Ok so I got my multimeter and I put it on its 10m DCA setting, put the red connection in the COM and the other section on the earth battery terminal, put the black connection in the 10A and the other on the earth point on the car.

Got stupid readings until everything settled and all doors were closed and the usual stuff.

So I removed fuse 40, which I think is telephone, and got it down to 1.18
Then I removed fuse 40 + 9 and got it down to 1.09
Finally got it down to 0.01 after removing fuses 40, 9 and 3.

I can understand 40 because obviously the phone stays active for a while so if I put it back and waited long enough I guess it would drop. But what are boot fuses 3 and 9 for?

 

[John_Doe]

Hmmm can someone please enlighten me to what Fuse does what because I now seem to be soundless and hae no tv tuner or cd changer. Sat nav works and I can see the command screen but no audio or anything plugged in. Just tried putting fuse 40 back in just in case it was to do with the phone but still nothing. I knew I should have left it alone lol

 

[brigadier]

You have no sound after you put all the fuses back? Strange, maybe you can try disconnecting battery for a while. You should have a diagram what fuse does what.

 

[KurlyKris]

Just as an aside here, I would say 75% of batteries are replaced with no good reason because people don`t know how to charge them properly. I am an electrician by trade by the way.
An overnight charge on a reasonably high rated charger, say 11amp like mine, will not touch the deep charging cycle of the battery, you have to monitor it and test it correctly during the charging process.
I used to have an audi cabrio, which i used frequently for little trips, but always used the electric hood ( obviously )

The battery was always causing me problems !

I took it off and carefully charged it and tested it correctly, this process took 2 WEEKS to get it fully charged !
Once fully charged though, I never had another issue.

On a normal car the engine needs to run for 15 minutes above tickover ( alternator giving maximum output current ) just to replace the energy used to start the car.

You may be barking up the wrong tree, the battery may be sitting at minimum reserve capacity and in these cold damp days, just loses what little energy it has overnight.

I`ll try and dig out my notes on correct charging levels, voltage llevels and drop test procedures.

 

[KurlyKris]

Found my guide

Once you think your battery is charged, apply a load to it, say 50W 12v bulb for 10-15 minutes, this will pull 4 amps.
Disconnect the bulb, then leave tha battery for 15 minutes, then re-check the voltage with everything disconnected.

 

[John_Doe]

Well I replaced fuse 40 and 9 and left the multimeter connected for 15mins and I'm getting 0.02. Put fuse 3 back and the lowest I get is 1.18

 

[Diesel Benz]

What size was fuse #3 again? Which options do you have from the list in the figure?

 

[brigadier]

well the fuse 3 seems to be the problem. If it's taking more than 1 amp at standstill and you have let's say 50ah in the battery - it only takes 2 days to completely drain the battery. I had similar reading on my 300ce. turns out boot lid needed adjustment - boot light was still on when i closed it. Don't you have a diagram which fuse does what on a fuse cover or somewhere?

 

[Neil Mackay]

I think fuse 3 relates to the dome light and tv...if you have tv that is....my guess is there is a sensor in there not telling the command its time to goto bed and keeping that part of the canbus open! Had similar with my passenger seat module...

Edit....just re read the opening post...tv tuner not telling command its sleepy night night i would imagine!

 

[John_Doe]

I can't see any list of fuses on a cover. I found a list online but it only said it was for done lights not my tv tuner. But I should have guessed it was to do with the TV tuner as it no longer works lol.

So now what!? New TV tuner? I just spent £40 on a cable so I could connect something to one of the aux ports on it. Another cable for the drawer I guess