Or something is draining your battery. Left the radio on? Is the immobilizer / alarm working OK? Brand new batteries can also just die for no apparent reason.

In some part of switzerland, you have some sort of weasels (fouines, in french), eating the electrical cables. Have a look at the cables, if they have some bite marks in it.

My car is about 2 years old and the battery was dead after 2 days in my garage. Turns out that it was a faulty "module electronique" (some electronic gizmo that controls all the electrics) that completely messed up the electrical system causing it to drain the battery.  They needed to order a new module and now everything's fine.  Like the man said, new batteries don't drain for no reason.

Except he didn't say that - he said they could, but it would be unusual.

If air humidity is high (rain, fog, rather humid garage "climate"), this can make a battery die when being exposed to it for a while (happened to me, it only took 8 hours).

Or when the electricity of your battery goes somewhere else without you noticing it (creepage current).

If you have problems like this with your car's electrics I strongly recommend that you take it to an auto electrician specialist and not to an ordinary garage.

Hate to be absolutely moronic but 1. if the garage fitted it or charged why do you not ask them to sort it out? 2. Are you not a member of the  TCS which costs almost nothing

thanks for all this info!

as my car is actually rather old and never had any problem whatsoever, i somehow doubt it's the electric system, and as it was in the garage for 2 weeks, doubt it's humidity/water. i will definitely check the possibility of an animal having bitten through the cables, though...

i'd never heard of the electricity leakage!  how does that happen??

Paul: in fact, my old battery died while my car was parked at home, so i bought a new battery and got a friend to change it for me as i couldn't get the car to the garage. i will, however, definitely talk to the people where i got the battery to find out what the hell is going on. and i know i should be at TCS, but as i live in France, i still haven't got around to it  :( i know it's no excuse, but there you go!

My last car never gave me any problem whatsoever also, (had it 15 years).However on the one occasion it would absolutely not start, (it must have been 12 years old at that time), even though it had a nearly new replacement battery and despite theTCS trying everything, it had to go for a full check to the garage where they found it was the part governing the electrical system which needed to be replaced. After that was done, it was fine again for the rest of the time I had it.

just wanted to say thanks for all your answers! the car's set for an MOT on Tuesday, so hopefully, the problem will be solved.

An MOT wont pick up on electrical faults. You definitely have a short somewhere. If the car is old check the lights for cracks or holes. I know this sounds like a long shot but I've known rain to get in to a light and cause battery discharge. 

Alternatively your only other route is an auto-electrician who will test the system for you and pin point the source of the drain.

Hopefully its nothing 'spensive :) 

My mum bought a brand new VW Fox - she has changed the battery THREE times since - having complained A LOT to the garage the answer from VW is that she simply is not driving enough in her car (?!)

She drives only little trips daily/weekly and every time the car stands a little more than a week the battery is flat.... 

So apparently that can also be a reason :-)

This week I will be too busy and next week I will be not here in swiss.. Otherwise I would come to you and check your battery and alternator....and the consumption of your car if everything is off.

The technical term is "Ignition Off Draw."  It refers to the sum of the currents that flow in the car's electrical system when the ignition (key) is off.  It's simple for a mechanic to measure.  Assuming that it's within normal specification, attention should be focused on the charging system and on the battery itself.

If IOD is high, things get a little more interesting.

wow, am i getting information i never dreamed of! ;)

Andreas, thanks for thinking of taking the time to have a look at my car. that's really nice of you! next time, i'll know who to call :)

rest assured that i specified they should have a look at the battery charging (or whatever IOD or other!) while they were at it. we'll see what they say tomorrow evening...

Buy a pushbike, and use it........best regards!!

ale

(a brazilian by mistake...)

i like the idea od the battery tester (and its price, compared to a battery! thanks for the tip)

but... if something was draining my battery, the tester would still tell me it was empty, wouldn't it? i mean, it can't tell why it's dead, only that it is, right?

Yes that is right Minda. The tester cannot tell you why the battery is dead or where the leakage is.

Actually the car system is always draining a bit, but not so much that there isn't enough left to start your car. With te 'car system' I mean the locks, computer, ODO, radio, clock, etc, etc.

After reading the thread I guess it's a shortage somewhere. I had that once and is really difficult to find.

Good luck.