B7 TDi Dead battery after 10 days away!

**Sam2012** · 12-08-2012, 10:38 PM

After returning home from a short 10 day holiday my new passat had a flat battery, after getting roadside assistance to help get my car going again I was told I had to book my car in for a recharge as it has a special type of battery for the stop-start technology. When I called to book my car in, the service person told me that it was normal for a battery to die on a car after such a period and that charging the battery is a service and would incure a $115 fee.

My question is has anyone else had this problem or does anyone else think it's reasonable to assume your car will be fine after 10 days away?

The car was locked in my garage with no lights left on.

**Transporter** · 12-08-2012, 10:46 PM

It really depends how you use your car. If you drive short trips only, the battery will never receive full charge and will go flat fast if you leave the car for few days standing.

The battery in you Passat is AGM battery and it is very expensive one. They should be charged with the charger that is designed to charge AGM batteries.

**Sam2012** · 13-08-2012, 09:05 AM

To me it just seems to be a bit odd, I do a mixture of short and long trips in the car. In the past I had an i30 and when I went overseas for 8 weeks it started instantly upon my return.

The passat's battery was so flat that the car started in German, the roadside assistance guy was surprised that there wasn't lights left on. He couldn't understand how it could be so flat.

**CaseySP** · 13-08-2012, 11:16 PM

This is interesting. On our last test drive of a TDi we took it home to check if our baby seats would all fit. I noted to the dealer that it was odd that the start/stop hadn't activated at all on the drive (a previous drive in the TDi had it shutting the engine down at every opportunity). Parked the car on the driveway, confirmed the seats all fitted, then went to start the car to drive back to the dealership and nothing. Completely dead. The dealer said the car had been sitting for a couple of days, but it is still concerning that this would happen. Don't know how it was started at the dealership - we didn't see that part.

Worried now about leaving the car sitting at the airport when we take our Christmas holidays.

**MJW** · 14-08-2012, 03:52 PM

Not sure of the differences in batteries to the V6 but I had mine sitting for 15 days (with alarm activated) & started first go as if it was only 1 day. I do drive 80 klms per day though so assume my battery is always on full charge.

**Marakai** · 14-08-2012, 07:38 PM

Can you charge the Passat AGM batteries yourself with an (AGM) charger? Or is that going to void some warranty?

It'd be much easier if you just charged it enough to start and then finished it off with a longish drive than bringing the battery in for service.

**VAG newbie** · 15-08-2012, 01:34 AM

Originally Posted by Sam2012

After returning home from a short 10 day holiday my new passat had a flat battery, after getting roadside assistance to help get my car going again I was told I had to book my car in for a recharge as it has a special type of battery for the stop-start technology. When I called to book my car in, the service person told me that it was normal for a battery to die on a car after such a period and that charging the battery is a service and would incure a $115 fee.

My question is has anyone else had this problem or does anyone else think it's reasonable to assume your car will be fine after 10 days away?

The car was locked in my garage with no lights left on.

This is really concerning. IMO, there must be some faults with the battery or some sort of electrical problem in your car that is bleeding electricity.

Normally for an older battery, you expect it to die in about 10 days, but not for a relatively new battery. For a B7, which was only released about a year ago, your battery can't be that old, unless you rarely drive it (like driving it once every 2-3 days, and only short trips) So there must be a fault somewhere. I think it is quite irresponsible for the service department to tell you that. I would seek a second opinion. I suspect your service department just don't want to honor the warranty.

I am thinking of getting a Passat wagon myself. But hearing this, it is quite concerning, especially we do a family trip at least once a year and leaving the car in the airport carpark. Really don't want to get stranded in the airport.

**BlackSuperb** · 15-08-2012, 04:34 AM

Originally Posted by Transporter

?..The battery in you Passat is AGM battery and it is very expensive one. They should be charged with the charger that is designed to charge AGM batteries.

AGM batteries are expensive but you don't need a special AGM charger as any 2 or 3 stage chargers will suffice. Just ensure you don't overcharge your AGM if your charger is the basic type. Stop the charge at 14.7 volts but 14.1 to 14.2 is optimal.

To the OP, you have a battery drain issue, the service guy you spoke to doesn't know what he is talking about. Send your car to a repair facility for a warranty repair and don't take no for an answer.

**Transporter** · 15-08-2012, 08:47 AM

Originally Posted by BlackSuperb

AGM batteries are expensive but you don't need a special AGM charger as any 2 or 3 stage chargers will suffice. Just ensure you don't overcharge your AGM if your charger is the basic type. Stop the charge at 14.7 volts but 14.1 to 14.2 is optimal.

To the OP, you have a battery drain issue, the service guy you spoke to doesn't know what he is talking about. Send your car to a repair facility for a warranty repair and don't take no for an answer.

The float charge should be no more than 2.3V per cell, and one has to watch the temperature as well, because the AGM batteries don't like overheating. Hence the need for the dedicated charger. The Passat and any VAG car with the stop start has the proper battery managment system.

Anyone interested, can use the VCDS to see how the ECU is monitoring the battery.

So, before you connect the battery charger to a car, take a one step back and thing, what charger and where you connect it?
Unless you want to remove the battery and charge it out of the car.
Ctek and Projecta have battery chargers that can charge the AGM batteries. The float voltage shouldn't exceed 13.8V on these.
Happy charging!