My AGM battery in my Passat is nearly 4 years old. It tests between 35/40% state of health after only 4 years. Start stop still works but when it’s cold you can hear the starter doesn’t have the same kick. I don’t think even AGM’s are immune from start/stop abuse.

 

My fathers 14 year old Passat is still on original battery.

Edited 13 January, 20215 yr by Micky 32

AGM are built for 10 years worth of regular use in S/S applications. 
 

No lead acid battery can cope with long periods of inactivity leading to deep discharge (measured over many multiples of weeks), being held in a low voltage condition for longer periods of time (low mileage vehicles), or long exposures to heat. Just one significant event such as these in a batteries life is a nail in its coffin. 
 

Then theres the taxi duty cycle that does the opposite and overworks them. 

i have just started having this issue, i have a dash cam in but its wired to the ignition so only uses power when engine is on, car runs ok but occasionally automatic central locking wont work, dont use start stop so can i just ignore this or is any harm being done to the car ??? thanks 

i also get a fault "passenger compartment over average temp"