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Hi all

I'm looking to replace the battery in my '08 3.0 TDI Treg and have been looking into upgrading to an AGM battery for a variety of reasons. This is my first battery replacement since buying the car in 2012 so am pretty happy with that!

I rang up my local car battery supplier and they advised that unless my model was designed for an AGM that I might have problems as they require a different charging profile - i.e. higher voltage and current. They went so far as to suggest that Tregs designed for AGM batteries have a completely different alternator and, while my car would still charge it over long trips, if I did shorter trips it would mean the battery wouldn't charge as well as a like for like lead-acid replacement.

Was very dubious to say the least. I did some further research and it turns out that AGM batteries actually prefer lower & slower charging cycles so now I'm not sure what to believe. I also understand that Treg's actually monitor the battery to ensure that the correct charge is being applied to the battery.

My question is...Is any/all of this true? Are there any issues replacing my battery with an AGM (other than ensuring the correct size)? I was looking at the Varta G14 as the AGM of choice.

Cheers

Matt
 

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Respected charger manufacturers like CTEK use a higher voltage when charging AGM compared to wet lead acid - perhaps you can quote your source and explain why other experts are wrong
 

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Respected charger manufacturers like CTEK use a higher voltage when charging AGM compared to wet lead acid - perhaps you can quote your source and explain why other experts are wrong
Hi Black Grouse. The info I found is summarised here:

I'm less worried about external chargers as opposed to the information I was given from the battery store that said my alternator wouldn't charge an AGM battery properly.

Is it true that my '08 Touareg monitors the battery and adjust current and voltage or is this only in later models which have Stop-Start technology?

Basically I don't want spend the extra money only to find it won't last as long or be charged correctly. So am happy to hear from anyone who can provide advice.
 

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I put a varta agm battery in my 2004 v6 3.2 two years ago. No issues so far. Treg spends most of its time in the garage on a cteck agm compatible charger.
If you decide to go for an agm you can find a compatible one on varta website. They have a battery finder tool.
My 04 does not have any sophisticated battery management system. I might be wrong though. I did go through the same process but decided to go for agm for security reasons only I guess (sealed battery). I was reading all kinds of info on the web too. Varta suggested three batteries. Agm was one of them. I will look up what batteries vw is putting in your model.


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WOuld you risk it if you didnt know ?

Did the Germans do something wrong using Varta ?

Why wouldnt you go with what is / has been blessed with using a certain product. I have a gut instinct the Germans thought about what they wanted more than once or twice ... or any commodore part from Repco someone would whack onto a rubbish v8 station wagon ..
 

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Go Varta and get the best you can !
 

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Sorry I’m not following you there Odesa. Can you rephrase your comment please?


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AGM's are snake-oil BS marketing.. for an automotive starter they provide no benefit for the extra expense... it will last just as long as a flooded battery, because chemically they are identical.. AGM is just a lead battery in the end, and one that is more sensitive to abuse and will fail earlier from neglect than a normal flooded battery.
 

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What you said is true as far as it goes- but there are differences. AGM batteries are more resistant to physical abuse. AGM batteries can still be used with a broken case. AGM batteries are more resistant to vibration, and are truly maintenance free.
While flooded lead acid and AGM batteries both use electrolytes and lead plates, the construction is different between the two. Flooded lead acid batteries have the electrolyte as a liquid around the lead plates while AGM batteries have the electrolyte in fiberglass mats. AGM batteries are a true maintenance free battery.

Are AGM batteries a magic bullet against all battery issues? No. Maybe that's what you mean by "snake-oil BS" Would a high quality flooded lead acid battery be just as durable as an AGM? Yeah, as long as the case wasn't compromised. Don't swing the voltage too far either way when charging and don't deep cycle (past 50%) and it's fine. You make your money back in longer service life.

AGM is a tool in the tool box. It's really that simple.

AGM's are snake-oil BS marketing.. for an automotive starter they provide no benefit for the extra expense... it will last just as long as a flooded battery, because chemically they are identical.. AGM is just a lead battery in the end, and one that is more sensitive to abuse and will fail earlier from neglect than a normal flooded battery.
 

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Its snake oil in that everyone tries to upsell you on using em and nobody buying em gets to utilize their advantages for the extra expense, there's a ton of marketing bs behind it and even more garbage quality AGM's out there priced higher than quality FLA's.

So of any of those advantages you just listed, I've never had a battery fail from physical abuse, vibration, or broken casing.. and that includes purpose built off road vehicles, those kind of failures are pretty much unheard of, your battery will age out before it physically falls apart.. so your spending more money to hedge against a failure that almost never happens.

AGM's real advantage in Automotive industry is that it can output tons of amps in a small factor.. If you want to take out that 100lb lead battery and replace it with a 30lb AGM sized for a motorcycle/lawn mower you'll find it has enough CCA to get your motor going for a fraction of the weight.. thats worth paying more money for, at least on vehicles where your paying a ton of money to shed weight.. like race cars or overland vehicles.

AGM in industry are really only suitable for large house banks, where you can coddle their charge parameters, and operating temperatures and stretch their lifespans out into the decades, many of the advantages AGM bring to the table you are able to utilize in these kind of situations .. but you need quality AGM for that and the price of Rolls/Lifeline is quickly being overcome by Lithium technology so even this Niche where AGM's shine is about to be snuffed out.
 

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One thing to remember, the battery is located inside the car, lead batteries do outgass, AGM don't..they're sealed and maintanance free.
So, who would like to live with that poisonous gases inside his car?
 

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oh thats some FUD right there.. Yeah they outgas if you overcharge them to the point you boil away the liquids.. and you know what that dangerous poisonous gas is? Hydrogen, the smallest and hardest to contain element.. the earth cant even contain it, every atom that is vented to atmosphere eventually is released into space.. if your vehicle is an absolutely perfect vessel and you hooked up a dumb shop charger with no stages you might be able to concentrate enough hydrogen gas to make a small pop.

Thats why we have DC charging systems, to prevent overcharging the batteries.. After decades of making our vehicles, nobody even found acid spills under the seat let alone any signs of dangerous offgassing, if it was as serious as you think it is why in the world would smart german engineers even consider putting it there in the first place?
 

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oh thats some FUD right there.. Yeah they outgas if you overcharge them to the point you boil away the liquids.. and you know what that dangerous poisonous gas is? Hydrogen, the smallest and hardest to contain element.. the earth cant even contain it, every atom that is vented to atmosphere eventually is released into space.. if your vehicle is an absolutely perfect vessel and you hooked up a dumb shop charger with no stages you might be able to concentrate enough hydrogen gas to make a small pop.

Thats why we have DC charging systems, to prevent overcharging the batteries.. After decades of making our vehicles, nobody even found acid spills under the seat let alone any signs of dangerous offgassing, if it was as serious as you think it is why in the world would smart german engineers even consider putting it there in the first place?
I take it you've never had a charging system go faulty and overcharge the battery?
 

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I've had vehicles that had just a dumb constant voltage alternator that could cause a little spilling under the hood if you took em on long road trips.. thats just how they were designed.. back in the 70s-90s.. but now we have variable charging on just about all modern vehicles, that go into a float state to prevent overcharging.

I've had decent chargers fail unattended and take the battery out with it, but not because it overcharged the battery but because it stopped charging and nobody checked on it for 6 months so the battery self discharged and sat depleted for most of the time.. battery was physically fine, no acid spilt and nobody hurt.. but your talking about leaving a battery unattended forever on a charger with an infinite charge source vs putting one in a vehicle where your actually inside when its charging and available to see faults and cel's being displayed.. if your charging system fails, your car will soon die like everyones does when the alternator ****s out and the battery is empty.
 

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Not to stir things up, just clearing some things up...
Flooded lead acid batteries off-gas hydrogen when charging or discharging, which is extremely flammable in any concentration. Touaregs have a hose which connects to the vent of a flooded lead acid and leads outside. This is an essential safety feature- you should never charge or discharge a flooded lead acid battery in an enclosed space, nor smoke around one which is charging. They can also give off hydrogen sulfide gas when over-charged/over-heated. Hydrogen sulfide has a rotten egg smell, but if you can smell it, it's already at toxic levels. People have died from batteries in cars not vented properly.
I'm not coming down for or against any battery type. Just getting some information out there. Flooded lead acid batteries are as safe as houses when you understand and mitigate their dangers.
 

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I won't get into any technical arguments about the construction of specific battery types, but living in the interior of Alaska, battery performance is critical. I get about 5 years of life out of a traditional lead acid battery, and never more than 6 years. The DieHard Platinum AGM batteries in my E-350 van lasted 10 years; I replaced them with Odyssey batteries that are now 5 years old and still cranking great. My Touareg was noticably slower to crank this past winter with 4.5 years on the battery. It's battery will be replaced before winter. If I can find a reputable AGM that fits, that's what will go in. If not, I'll go with Varta or Interstate.

For what it's worth, my Ford is equipped with a single alternator that charges at 14.4 V and up to 140A for two 1000CCA AGM batteries. Batteries and alternator seem to coexist happily.
 
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