audisession

Does anyone know which agm battery I can use on my S8 and what the procedure is for registering the battery (on my BMW the battery needs to be coded to the car - not sure if I have to do that with vcds)

Edit : I have found the battery recoding procedure
But can I use an autozone agm battery?

Thx

MP4.2+6.0

One suggestion/tip. Do NOT get the S8 spec. battery. It is the smallest/wimpiest one spec'ed for any D4, which makes no sense other than some compliance move or faux weight shedding. They may think they can get away with it too because unlike others, no start stop on an S8. D3 anything also used bigger batteries as another reference point, in that era still pre AGM. There are a range of AH's for the car available, and literally any other USA motor uses a bigger one. From looking at it once, EKTA says the only other one that uses this battery is the piece o crap Hybrid sold only in Europe and China--the one with the humongous main battery pack jury rigged in the middle of the trunk that already handles starter related loads unlike the S8. They all fit in same spot under the spare, and typically the width just increases a bit with the size changes. The reason I harp on it is I have had incidents with mine already at high air temps (100F +) where Sirius drops out that I suspect in turn may be related to battery brown out conditions once fans go into overdrive when stuck in bumper to bumper. Pretty shocked when I found it's a 75AH battery, which is like a 10 year old Honda Accord 4 banger.

Almost all batteries here come from one of three suppliers: Johnson Controls (including Audi VARTA ones typically), East Penn/Deka and Exide. Thus many brands, from Sears to Interstate, to dealer OE, to store brands, come from the same suppliers. What distinguishes them are basic type, and quality of construction. You can get at latter to an extent by the specific ratings for a given size and by the warranty periods offered. Indirectly, sometimes you can tell who made it by the specifics of the case. Audi ones being the characteristic somewhat unusual with the vent tube sometimes give themselves away when you find other Johnson Controls private labeled ones. But it's still like a Duracell vs. Eveready vs. Kirkland debate--they all provide juice, and you can fake out the recode process. When its discretionary, sometimes the dealers offer battery coupon type deals; mine does about once a year. Did my last D3 W12 in the parking lot when I brought my wrenches to pull the core. And yes, I bought the "big boy" for that one too.

A 8

Great if you could share the procedure in case anyone else on here have the same question.

audisession

Yes I will post the procedure with pics

Btw is the battery covered under the new car 3 yr 50k mile warranty

MP4.2+6.0

Yes, battery is covered. Warranty is 4 years, 50K, at least in USA. The one in my D3 W12 was changed w/in the first year from the paperwork I got before buying it CPO. If obviously failing, easy to get changed out. Could even do it on a quick drop in basis.

audisession

Ok so even though I probably could have the battery replaced via warranty I decided that I didn't want the possibility of a no start situation in morning or the hassle of them running diagnostic on the battery, trickle charging it etc and keeping my car for a couple days so I headed to local advance auto parts where they were offering 20 percent off for batteries and they had an agm 900 cca (but only 92ah) battery on sale for $140 with core deposit

Battery is under the trunk
You have to remove spare tire and the styrofoam things holding your tools
Then you'll see a big metal piece holding the battery down
There are four bolts - you need to use a 20mm socket with extension to remove the four bolts holding the metal battery bracket - you will have to peel the carpet back a bit

Then using a 10mm socket disconnect the positive and negative cables and set them aside

Remove the battery

Put the new battery in

Reverse everything and replace it all

Now you have to use vcds to code the battery

Select module 19 CAN gateway
The most important thing to code is the battery size which is in Ah
My generic auto parts battery was made in Germany and rated 900cca but the Ah (amp hr) was not marked. So googling revealed that it was a 92Ah battery

I left the manufacturer as unknown and typed in the serial number marked on the battery

A few symptoms of a dying battery:

1. Extra long crank before start - you can feel / hear that little extra hesitation
2. Eventually I got the "battery level low - drive vehicle to charge" warning
3. Headlights would intermittently not come on when the door was unlocked (welcome lighting)
4. Hooked up voltmeter at the battery terminals - consistently 11.8v dropping to 10.8v

So far so good on the new battery

A 8

Thanks Audisession, I am sure it will be useful for many of us as the cars get older.

Uber.8

If not an OEM battery replacement for a '16 S8, what battery would you recommend? Would the dealer install an aftermarket battery at the customer's request?

audisession

I just picked one up at the local advance auto parts store. All car batteries (including the factory one) are made by 4 vendors, and the one I bought was made in Germany as well as most AGM batteries are.

You can buy one at any auto parts store - it's a H8 sized AGM battery.

I don't know if the dealer will install an aftermarket one.
You can call and ask - but I doubt it

MP4.2+6.0

Here's a picture of the 2015 S8 factory battery in mine that I was mentioning earlier in thread. As I said only 75Ah, so wimpy for a high electronics vehicle, with a V8 to boot. Sounds like you got a more more reasonable capacity one.