Charging car battery via the accessory socket?

[mikedjay]

Hi all
Having recently suffered the dead battery problem has lead me to wonder which battery is the jumpstart positive post connected to, the small one in the front, or the larger rear one? Yet to find a decent set of wiring diagrams to work it out.
Was thinking of getting a solar charger to keep the batteries topped up as my car is not used as much now and maybe using that post as the connection point, or would one for each be a better idea.
All constructive comments welcome.....
Thanks
Mike

 

[LostKiwi]

Given the jump start terminals are there to start the engine it will be the starter battery.

 

[mikedjay]

Hi Kiwi
Yes, obviously....
Thanks

 

[Graveworm]

Sorry to resurrect this thread rather than start a new one. I frequently park in the long stays. For some reason my new E63s doesn't seem to have standby mode or equivalent that I have always used on other cars. The most recent was 4 weeks and after 3 I got a warning from the App that starter battery was critical. It did start just fine and I have run it to full charge over a few days. I want to avoid this in the future as it is occasionally longer. So is there anything I can disable to eek it out. I have been recommended a solar panel that plugs into the OBD port. 6W or 2.4W. Does anyone know of any downside or have any other recommendations?