kajtek1

This is what I have in my 2 MB.
The main advantage of AGM battery is capability of working upside down, or on the side, what I have no use for.
Beside that AGM batteries don't prove themselves long-lived, seems the regenerative charging in newer cars is killing factor as well, but 1 of my flooded batteries is over 3 years old already.
Flooded batteries come with 96 months warranty.

Robuk

There are two systems at work here, stop/start and energy regeneration, I own a December 2011 C-Class 1.8 Coupe CGi petrol Blueefficiency which has Direct fuel injection,Turbo,Stop/start and regeneration, I have full service records and the battery is the original Varta AGM date stamped 38 11 on negative post, I purchased the car Feb 2016 and have always turned off the stop/start function, 6 months ago I found a way of deactivating both stop/start and regeneration by simply disconnecting the sensor on the negative rail of the starter battery, the EMU puts the alternator into a standard charging regime of between 13.8 to 14.4 volts as it cannot now read the SOC, the advantage of this standard regime is the battery gets to be fully charged instead of 75% as when in smart mode and you don`t get a 16 volt high charge jolt from regeneration. The car has now been running with this disconnect for about 6.5 months, other than loosing brake hold everything works as normal, no stop/start and no regeneration and no EML. The battery is now 7 years 5 months old, it tested this morning after resting over night at 12.67 volts and starts the car first time every time.

I also own a 2015 SLK petrol R172 blueefficiency (same system as C Class above), I compared the R171 SLK against the R172 at the web site https://www.honestjohn.co.uk for on the road fuel MPG, the difference is 1.9%.

Why JD Power Reports 44% More Car Owners Are Having Battery Problems
https://www.forbes.com/sites/jimgorz.../#158a1566323c

AGM AFTERMARKET FALTERS AS DRIVERS DISABLE START-STOP FUNCTION
http://www.batteriesinternational.co...stop-function/

Mr.Fly

If you're interested to know, why not just pop the hood and look inside? The label on top of the battery should say definitely if your battery is AGM or otherwise. The original battery in my car was made by Varta and labeled as AGM. It lasted 6 years and was still functional before I proactively replaced it to mitigate unwanted surprises. I don't have Start/Stop though.

kajtek1

No CEL ?
Interesting concept, although not usable for me as I love ECO stops while spending long minutes at red light and my DPF equipped diesel has to have regeneration. The highest voltage I see is 14.7V
Than like article says - 5% fuel savings give me at least $50 a year (we don't drive cars much) so saved money pay for new battery every 3 years.
To make it clear - I have flooded main battery, but still AGM for ECO. But I bought small battery at FCP and they give lifetime warranty.

NickTH

Update:

With one week left before our 2015 E400's 4 yr orig factory warranty is up, went to dealer to have battery checkup & Nav update.

Service Advisor called 2 hours later, said battery has low voltage, so they replaced for free, & Nav updated.
Got our vehicle back, we checked the Nav version, it still shows 2014/2015 (V 12.0) N America version. Informed Advisor. He checked & said Sorry, new version is NTG4.5 Command & costs $99, will take an hour to install. I asked any extra cost for installation? He said No, the $99 is for the cost of install labor. An hour later, got our car back & checked, new Version 2019 (V19.0) was installed. Advisor said Don't worry about the cost, it's Free. So both new battery & Nav update were totally free since we brought it in before the 4 yr warranty expired.