My 1.2 TSI Roomster has a great appetite for flattening batteries, I'm on my 3rd one! It had done 30,000 miles when I bought it, the battery looked very poorly, so changed it. I had a period of illness, so was advised no driving until we give you the OK, I was surprised to find this battery was utterly dead, no amount of charging would stay in it for more than a day! The dealer put it down to non use, and refused to replace it, even though it was less than 1 year old. Fitted another top quality battery 10 weeks ago, and found that the draining was still happening. I've checked the Glove Box light, the 2 lights in the cabin, the light in the boot, all definitely out after closing the doors and locking it. I've checked the motorised mirrors, both cool to the touch. Took the car out yesterday, seemed to struggle to start, but assumed a couple of miles run would tickle it up to start for my return. Wrong, I was stranded, not even the hazard lights would work! Luckily a friendly resident jump started me, so got the car home again. Charged again for 24 hours, seems OK, but confident that within a few days, it will be drained again. Any ideas anyone, if not I'll have to take it for a Diagnostic Scan.

 

I'd just jump straight into the diagnostic scan. Far better than stabbing about in the dark.

If it points out the probable cause, good idea. I'm sure that Bristo's told me previously that it would cost around £100 + VAT + whatever the repair turned out to be! I'll put details on here of what the scan found, hopefully they might fit me in the next week or so.

Someone local to you might be able to help with a scan. If you're near North Yorks I'll do it for you, otherwise check out the VCDS owners map.

Thanks very much for all the info, I'm in East Anglia, so I can see that there are a few on the map around Sudbury, Colchester etc.

 

Regards

 

Peter

Would a scan show up this sort of thing ?

It'll show up any faults present, which could point to the cause. It won't tell you "The glove box light is staying on and flattening the battery!".

I believe that I've made an interesting bit of progress. My TomTom SatNav is fed from the Cigar Lighter socket behind the gear stick. This socket is alive all the time, ie it doesn't go off with the ignition. My Sat Nav is never left in the car, so it is an open ended feeder in effect to the cradle on the windscreen. It is too long a stretch to use the cable supplied so as the DC input socket on the cradle is similar to a mini USB socket, I bought a flat USB lead + a TomTom plug which looks similar to a cigar lighter, but has a couple of standard USB socket outlets to feed 12V to whatever you are connecting to it.

This TomTom plug has a tiny green pilot light on it to show when it is feeding the SatNav in my case. It must therefore have some electronics inside it so I brought it in to my 240 / 12V 30A PSU used for amateur radio. Unfortunately the scale on the amp meter goes up to 40A, but on plugging this "Cigar Lighter" adaptor in, there is a slight kick on the needle so it seems that this unit is causing a unknown amount of drain 24/7 on the battery, in addition of course to the on board computer, locking system + alarm and radio. 

I'm now topping the battery up until the "Charge complete" light comes up on the charger, then give it a few days to see what happens. I've also checked the standing voltage across the terminals as 12.9V, started the engine, it rises to 14.5V on tick over, so the alternator is charging OK. Unfortunately the medics have advised me to stay inside during this very hot spell following my Heart problems, so this will give me time to see what happens now this plug is removed!

 

I have an Audi S4 2011 car and it sleeps in the garage most of its life as we tend to use wife's Polo, now this Audi has a AGM battery and they are expensive and don't like getting/being discharged, so it tends to be connected to a CTEK battery charger all the time it sleeps in the garage, I tend to test my batteries at every service and after 7.5 years the AGM battery in the S4 is still looking good capacity wise. I'd expect that your Roomster started life with an EFB and should still have one fitted - I need to check wife's August 2015 Polo's EFB to avoid disappointment!

It if turns out not to be your 12V cigarette lighter adapter then take it back to the garage who sold you the car and who changed the first battery for you.

 

If I'm reading what you've said correctly, then you replaced the first battery with a second battery that also failed.

 

That would suggest to me that the garage's original evaluation of their fitted battery was wrong (non-use).

Car manufacturers design electrical systems and batteries to last at least a month when unused.

 

For example my Superb has a 59Ah battery. It also is what is called a microhybrid (has stop/start and some mild energy recovery). That means the battery is rarely fully charged but usually 70-80%. Remembering that you will need charge to start a car, and a very low charge is not good for battery longetivity, let's say don't let it drop below 30%

So how long does it take for a 59ah battery to go from 70% to 30%?

I've measured the drain on my battery when the car is stood, locked up and it's on average around 15mA (0.015A)

 

So at that rate it will take 59x0.4/0.015 hours. That's 1573 hours or 65 days!!

The main dealer has finally acknowledged that there is some discharge going on and will do a full diagnostic check when I have a service + MoT in a few weeks time. This way will be cheaper than a special diagnostic he says. The vehicle will have a long run in a few days, so be interesting to keep a note of the voltage deterioration after then! The tyre pressure alarm went off a few days ago, one mile into a journey, no apparent cause found yet! Maybe some loose connection somewhere, I'm sure the computer will flag up any problems, but not necessarily a location!

re TPMS.

When you checked all 4 tyre pressures cold after the TPMS alert to see that all 4 were as when checked last time when cold & the TPMS set were they exactly the same?

 

At last, my service was due and I asked the dealer to do a diagnostic test, the result was as expected, NO fault found on the vehicle, but the battery had failed! So four batteries inside 2 years? They suggested that there had been a shipment of counterfeit Bosch batteries and I had one of them! Trawling through internet, I did find a warning that this was correct, unfortunately my actual battery had been scrapped and collected from their scrap area. A new battery was fitted but I still felt that it was discharging. All internal lights are switched off, the boot and glovebox lights are definitely off when the respective doors / covers are closed. I had been trickle charging every 2 weeks as before, but still found that spinning the engine to start after a cold night was sluggish. However a friend, who runs vintage cars came up with a solution that he uses during the Winter on his vehicles. I bought a trickle charger which has a set of jumpers to attach permanently to the battery. The harness ends in a non reversible plug inside the Bonnet and the car is now left with a "shore supply"! I had left it for 2 weeks without charging on the main charger, it took 48 hours before the trickle charge unit cut out, so it is indeed still draining, and no-one knows why! All I have to do now when I use the vehicle is to unplug the trickle charger and close the bonnet, and hook it up again on return!