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2001 Passat GLS 1.8T manual, satin silver
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I’m about a week late to this thread but I’ve lived where PZ lives and where Andreas lives (WI and AZ) and can tell you that heat really kills batteries. Cold just seems to temporarily keep them from putting out amperage.

VW’s position is that flooded lead acid batteries should be used as replacements except for newer cars that had batteries in the interior, which were AGM. I think I read this in TechConnect or some VW literature.

I wouldn’t waste money on an Interstate battery. They’re just rebadged, mostly from Johnson Controls, and hilariously expensive. When I lived in Arizona the Autozone Duralast Desert battery was popular. I think it had a different plate design to avoid case swelling from heat. Not sure if these are still around.

I had to chase down a drain in my Passat. I finally found it when I opened the passenger door in the dark with the dome lights off and noticed that there was light coming from the glovebox area. Doh! When I installed the Bluetooth kit a wire became caught up in the glovebox light switch mechanism!

It’s tough to diagnose drain with CAN BUS cars but there are some successful strategies I’ve used from some of the service literature and trade magazines.

Good luck!


I ran an AGM battery in my wagon too. It lasted 4yrs and 4 months. No issues, but it only lasted 4 months longer than the regular batteries did.
 

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Hey, I'm late to the party! My wife's Audi Q5 has it's AGM battery down low and adjacent to the spare tire, likely the comparatively coolest location. It was about 9 years old when the engine starts began to sound labored. I ended up doing what I had never done: buying a battery from the dealer's parts department. That was because the factory battery is supposedly optimized for the Audi's charging system. It was my first experience with a battery installation that had a current-sensor on the ground cable. Her car didn't need the battery adapted/coded like later Q5s do.
 

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Just for the record, I've been using AGM batteries in my Passat's for a number of years while I was still back in WI and I've never had an issue before.
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I ran an AGM battery in my wagon too. It lasted 4yrs and 4 months. No issues, but it only lasted 4 months longer than the regular batteries did.
Good to know you both had success. I've been thinking about AGM on my next battery change, partially because of battery leakage I've experience with my other vehicles. But then again, I had very good success with OE VW batteries in the hot 100°F plus summers we have here including no battery leakage.
 

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It's been a few years but the last time I needed a battery for my Passat I found the battery from the dealer both very high quality and reasonably priced. If you have a dealer nearby ask for a price.
 

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2004 GLS 1.8T
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Me too. Battery from the dealership is one of the best and cheapest options. I usually wait for a coupon and replace it every five years, regardless. Once when I let it go, it crapped out at eight years.
 

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Discussion Starter · #26 ·
The next time I need a battery I'll check into the dealership. I've already invested the money on these Interstate batteries. The one that came out of my 1998 GLS, that one came back ok. They put a low volt - high current charge on it and it brought back the cells to nearly 100%. When I took that battery in it was at just a shade more than 8 volts with next to zero amperage.
It sure spins that engine over pretty quick now.

The battery for my wife's GLX is another story. That one to is than a year old so I'll be getting that one replaced for free. I just gotta find the time to get it done.
 

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The next time I need a battery I'll check into the dealership. I've already invested the money on these Interstate batteries. The one that came out of my 1998 GLS, that one came back ok. They put a low volt - high current charge on it and it brought back the cells to nearly 100%. When I took that battery in it was at just a shade more than 8 volts with next to zero amperage.
It sure spins that engine over pretty quick now.

The battery for my wife's GLX is another story. That one to is than a year old so I'll be getting that one replaced for free. I just gotta find the time to get it done.
That would be high voltage - low current.
If the charge of those batteries drops below a certain level, they require about 14.4 volts to initiate a charge.
 

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I had the same issue with my wagon battery. I could not charge it with my home charger, but the new owner used the shop charger to charge it and it was fine after that.
 
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