A207 Eclass cabrio auxiliary battery charging

[rgv250ads]

Hi, I've got a 2016, A207 E400.
Has an auxiliary battery near the spare wheel well under the boot floor.
I have the main battery on a CTEK charger.

My question is, does the auxiliary battery receive a nominal charge whilst the main battery is on the CTEK?
My thinking is, surely the auxiliary is somehow connected up the the main 12v loom via the main battery and alternator, so I'm assuming with the car on a battery conditioner the auxiliary battery is being kept in good condition.

Your thoughts on this guys n gals.

[Scrump]

I wondered the same with my E class.
Eventually I put the Ctek directly onto the aux battery just to be sure.

[Monkeylegend]

On my SL I connect the charger to the auxiliary battery in the boot and this keeps both batteries fully charged.

If I connect it to the starter battery it only keeps the starter battery charged.

[rgv250ads]

Scrump said:

I wondered the same with my E class.
Eventually I put the Ctek directly onto the aux battery just to be sure.

This.
I decided to message my MB Indy, here's what he said:
"The main battery is only connected to the Aux battery when the relay is engaged by the SAM unit, this would not be active when the engine isn't running so thus would not charge on a CTEK, hope this gives you the answer. Cheers Steve"

So, auxiliary battery doesn't get a charge when you connect the main battery to a CTEK or similar.
Will probably pop the CTEK on the Aux battery for a few hours every couple of weeks in that case.
Posting back so anyone who searches for this post can see an answer