E270 Battery

[AntMB]

I've only just bought my S211 E270.

Well went to start the car last night and the battery was completely flat. I guess it didn't survive being left for too long. The dealer had previously charged the battery up, so we couldn't understand what's happened, apart from the battery has damaged cells from being left for so long, so doesn't hold charge for long.

Dealer agreed to give me the cost of a new battery. I found that the main dealer was cheaper than anywhere else.

Battery terminals hovering over 14V with the engine running, so the alternator is good so far as I can tell.

Now, I understand that there's a backup battery? What do I need to know about this one and what should I be checking? What does it actually do?

Thanks.

 

[MercedesDriver]

auxiliary battery what is if for?

 

[Major774]

Start with the fresh new battery in, monitor and see how long you can go before it goes flat.

If it is only a few days then you have yourself a battery drain issue. It will require some investigation work to find the source of the drain on the system.

 

[AntMB]

I've been monitoring it over the day, it's happily sitting at 12.8v. I'm hoping any sufficient load would put enough volt drop on the battery to read closer to or less than 12v. I'll check again tomorrow and maybe measure the current draw if there are any issues.