IsaacMTC

2005 Cayenne S...I had a dead battery one morning, out of the blue. I jumped the car and left it w/ my mechanic for the day. He installed a new Interstate battery. Everything was fine for a few days and now it can't hold a charge overnight. Having to jump every morning. Mechanic wants me to bring it back in...thinks maybe if I have a 2nd battery in the back it may be pulling current from the new battery.

How do I know if I have the 2nd battery w/out pulling out the spare tire and subwoofer? Would it be under the subwoofer?

Any thoughts. Replacing the battery is getting expensive.

IsaacMTC

I went and pulled the spare and subwoofer. No battery. I must not have that option, it's not on the window sticker. What could be sucking my new battery dry? My mechanic, who specializes in vdubs and porsche is almost at a loss.

IsaacMTC

I'll add another thought to my thread here... Could there be something that is stuck on, electrical wise that is draining the battery.

seankrider

Too late now, but the easiest way to tell is no wire running from the main battery back to a second battery.

KMCTT

Are other systems slowly shutting down, like the airbags, radio, A/C ect? Do you or have you had "Electric- Loads-Switch off" displayed on your center screen? I had the very same issues with my CTT and the problem ended up being the alternator. A royal PITA!!

IsaacMTC

Not sure what you mean by "electric loads-switch off"

Mechanic said that it could be a bad diode in the alternator that is sucking the battery dry when not running. Just doesn't makes sense to me. If the alternator charges the battery and the car is good all day, sitting 5 hours at a time and fires right up, how is that bad? It's only overnight that kills it. He ran a test w/ a new piece of equipment which said "replace battery."

He is very confident that it's not a bad battery. Alternators aren't cheap

Dennis C

Don't discount the possibility of a bad battery. I had a new battery installed in my Cayenne by my dealer a few years ago, and it failed within a week of the installation. They gave me another one at no charge, but it was still a PITA.

seafeye

A friend got a new battery for his boxster. I spent a while trying to figure out y it wouldn't hold a charge. Turns out the battery was the wrong one. Just 1 part number off. Anyway it would seem that a 12v battery is just not a 12v battery.

IsaacMTC

I was told that the cayenne battery is the same as the one for the toureg. Is this the case or not so much??

hahnmgh63

Yes, it's the same as the Toureg. A group 49 battery which is a fairly heavy duty one even by todays standards but more modern cars with lots of accessories like the Cayenne need a lot of reserve capacity. They have a lot of parasitic drain even when the key is off and a smaller battery wouldn't be able to start the car after sitting for a couple of weeks with a slight parasitic drain. Some years of the Audi A8 and the RS6 use the same large battery.