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Discussion Starter · #1 ·
So I went out to start my 1998 GLS this morning. Battery is dead again. :mad:
Gonna have to bite the bullet here and go get a replacement. I'm pretty sure it's less than a year old so I should get a free replacement. Sure hope so anyways.
Shelling out $300+ would be a major bummer after getting one so recently. Especially since my '98 GLS, the wife's '03 GLX and the '04 W8 all needed battery replacements within a couple months time.
 

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What batteries are you getting for that price? I can't remember the exact price, but I don't think I ever spent over $200 for an MPT-48 from Interstate (5 years going strong with sometimes weeks between starts.) Are you buying AGMs?
 

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Discussion Starter · #3 ·
Yep, MTZ AGM's from Interstate. Supposed to be one of the toughest batteries for the climate down here.
 

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Discussion Starter · #4 ·
Plus tax of course.

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It's been years since I spent more than $25 for a battery. I get mine at the junkyard 😁 They last 2 - 4 years or so. A $300 battery would almost total my Passat o_O (not really).
 

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The heat kills them fast. I've never had one last more than 4 years here, even with the Golf being parked in the garage for most of it's life. If I can get well enough to do some heavy lifting, I want to put the Tiguan battery in the hatch. Better balance and it should last much longer away from the engine heat.
 

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Discussion Starter · #8 ·
The heat kills them fast. I've never had one last more than 4 years here, even with the Golf being parked in the garage for most of it's life. If I can get well enough to do some heavy lifting, I want to put the Tiguan battery in the hatch. Better balance and it should last much longer away from the engine heat.
I've threatened to do that myself. That really would be the ticket.
 

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Yes, the heat is the killer. It was a smart design move to put the battery behind the “false firewall”, in the plenum, but then they ran the heater hoses through there to try and minimize the benefit they had gained.
 

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They also put the cats right under the false firewall.
 

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I've threatened to do that myself. That really would be the ticket.
Has anyone installed an AGM battery in their B5 Passat? I am just curious if the ECM will get confused with the AGM's different charging profile. I've installed an AGM in my classic Mercedes with no issues, but of course that car has no engine management systems.
 

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Has anyone installed an AGM battery in their B5 Passat? I am just curious if the ECM will get confused with the AGM's different charging profile. I've installed an AGM in my classic Mercedes with no issues, but of course that car has no engine management systems.
Looks like AndreasPassat already did.
 

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AGM batteries are sensitive to overcharging and undercharging. I wonder if the 1 year life was cause by one of these issues. It just seems odd as AGM is also supposed have better heat resistance than flooded lead acids. So I would think 1 year life even in Arizona would not be the norm.
 

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I doubt any battery will be under charged unless the alternator fails. The voltage regulator in the alternator should also prevent overcharging but that could potentially be an issue if the AGM requires a different float voltage than a regular battery. I've never heard of that being a problem but I'm no expert.
 

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Discussion Starter · #17 ·
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.

I recently made reference in another post while I was back in WI my 1998 GLS sat out in the elements for an entire year and the battery was just fine.
Down here I leave a car for a few months and everything just gets sapped out of it.

Who knows, there might be some parasitic draw on the car I'm not aware of. Like heated mirrors. :unsure: Should just yank that fuse out...
I've neglected that car so badly since I moved here to Phoenix, even worse yet in the last year or so.
I'll be digging into this issue in the next few days as it will become my primary mode of transportation again here shortly.
 

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Discussion Starter · #18 ·
Got both the '98 GLS and my wife's GLX running tonight. I'll take one of them to work tomorrow so I can stretch out the legs so to speak.
I was kinda surprised to find a full tank of gas in both cars. That tank of gas in the GLS has got be close to 5 months old. I can't remember the last time I actually put gas in it.

I did notice one thing, the master window switch control (in the GLS) is all buggered up. The rocker switches are crumbling from the AZ sun. Makes for some interesting window action. :LOL:
I've got some spares in a box somewhere. Good luck finding those right after the move. 😣
 

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Discussion Starter · #19 ·
Battery on the GLS was dead again. (n) Not even enough to keep the LCD display going. I knew right away as soon as I put the key in the door. No power to the locks.
Looks like a battery replacement is in order. Hopefully I can get some prorated price adjustment on a new battery.

So because the GLS didn't start I drove the wife's GLX into work today. Even this one cranked over a little slow first thing in the morning. After I drive it a bit I'll see if I can get the battery charged up a bit more.
 

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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.
 
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