W205 C63 battery issue ?

[RickMM]

Could do with some advice.

My 66 plate C63 is giving me the low battery warnings. Car still starts ok but had been left for about a week. I had it on charge for around 6 hours yesterday using a Noco Genius G1100 on the AGM mode (1.1A that I bought primarily for my bikes). The battery indicator on the charger went from below 25% to between 25-50% after 6 hours. Then after I turned the ignition on for a couple of minutes (without starting the engine) the battery was back below 25% again.

By way of background, it’s another case of the stop/start never working regardless of the type of driving I do (mostly faster A roads and motorway).

So, does the battery sound like it’s on the way out ?
How long should it take to fully charge ?
I've also got an old basic 4A charger (with minimal safety features). Would I be better off using that?

If so then is it something that’s covered under the 2 year AMG warranty which I still have?

If not covered under warranty and I can’t come to some agreement with my local dealer then can I just get one from Tanya batteries and fit it myself ? (or will the car’s software need to be told it’s got a new battery ?)

Lots of questions so thanks for any advice.

 

[markjay]

...So, does the battery sound like it’s on the way out ?...

It most certainly does.

Can't help with your other questions I'm afraid, someone else might have the answers.

 

[Lennox]

My AMG A35 has had the same error, but the cars been starting fine. Took it for a 15 minute fast motorway detour enroute to the supermarket and the error has gone.