My Mercedes C Class runs battery down while parked

[tamoshanter]

I bought brand new battery and put it into the car, didnt drive the car for 3 weeks as use a company car and was away from home for about week and half. When i went to take the car for a drive and enjoy her, the battery was as dead as dodo. Got battery replaced and have now taken to leaving the battery not connected/removing the terminals. As i said i rarely use the car

When i connect the teminals one of the them (live one) sparks a lot and unless the terminals are very tightly screwed it wont start


Any ideas please as i am at my wits end. Thank you

 

[telectrix]

if it sparks when connecting, then something is drawing current. a small current is normal. modern cars have ECUs, central locking, all pull a bit. try measuring the current drawn when everything is switched off. if , for example, it's 1Amp, then your battery will run flat in about 80 hours.

 

[tamoshanter]

if it sparks when connecting, then something is drawing current. a small current is normal. modern cars have ECUs, central locking, all pull a bit. try measuring the current drawn when everything is switched off. if , for example, it's 1Amp, then your battery will run flat in about 80 hours.

Thanks for your reply. How do i do this. Sorry but im a total newbie to this :shame: Off the top of your head is there something that comes to mmind as most likely culprit. Someone had suggested disconnecting the heater on the engine. The car is a C250 Turbodiesel you see and apparently they have a heater next to engine for the engine/fuel

 

[ruston]

And the battery may not have been fully charged when you bought it. Modern cars will draw current while standing , and need a good reserve of power to start the engine.

 

[tamoshanter]

And the battery may not have been fully charged when you bought it. Modern cars will draw current while standing , and need a good reserve of power to start the engine.

The battery was brand new. When i bought it and put it into the car i actually drove it for some distance and started up fine and stuff before i left it parked for the period in question. The battery before that had to died rather prematurely too but i put it down to repeated cranking/starts as we were fixing the car during repairs

 

[Earthstore]

Do you have a multi meter?

 

[tamoshanter]

Do you have a multi meter?

I actually have to google to see what that is

 

[telectrix]

If you're going to leave the car for 3 weeks standing, then it will go flat.

 

[Earthstore]

I actually have to google to see what that is

Oh.... You will need to take it to a garage or an autoelectrician then, it sounds like you do have something draining it, the tests are quite simple but you do need some knowledge of how to test..

Also your terminal will spark when connecting if the inside light is on in the car, IE the door is open.

I hope this helps.

 

[dan86]

Personally, if I was you I'd be tempted to get a trickle charger and stick that on it when it's not in use. I have a lot of customers that do this on classic cars, bikes, 2nd or 3rd cars they don't use very often.
By all means take it to a decent garage that can test the charging system etc, but I don't think you will find anything wrong with the car itself.

 

[telectrix]

apart from it being a rust bucket merc.

 

[dan86]

I was being polite!

 

[Darkwood]

Clamp meter and remove fuses and see when the current virtually disappears, i had this on my astra and it was the diode pack on the alternator ... it was drawing 60amps with engine off ... if ou crash the battery down to zero charge you may damage it so get a garage to do a load drop test on any battery affected see if its damaged beyond usefulness.

 

[dean.diy]

yes, feel's like something's drawing current whilst on the driveway AND the loose terminal's worth another look.

 

[ruston]

If you have a lose battery terminal the starter will not be able to draw the load required to start the car , the alternator may not get the full charge either, so you will always be on your back foot.

 

[tamoshanter]

Oh.... You will need to take it to a garage or an autoelectrician then, it sounds like you do have something draining it, the tests are quite simple but you do need some knowledge of how to test..

Also your terminal will spark when connecting if the inside light is on in the car, IE the door is open.

I hope this helps.

So is this potentially an easy fix for a garage or auto electrician

 

[dan86]

a decent garage will have it checked out in no time.

 

[ruston]

As above.

 

[Earthstore]

Ditto above.

 

[guest119]

There is a way to bring the battery back from way down zero, if you need to.

Boydy