E55 aux battery voltage?

[smoothcoupe]

Hi all I took reading from the auxiliary battery on my 2004 E55 , it was 12.97 with engine and ignition off. And with engine running it remained at 12.97 so no change... is this correct or should the voltage go up like the main battery. The sun battery readings are 12.4v engine off and 14.12 engine running... does this sound about right???? Thanks.

 

[smoothcoupe]

Meant main battery not sun battery... spell correction!

 

[toolman1954]

Hi,
Simple answer is that your battery readings for both batteries are on a par with mine, so there is nothing to worry about. The more complex answer is that there is a module that splits the charge and tops up the front battery as and when it needs it. I keep a voltage reader in the cigarette lighter permanently, just to keep my eye on the charge in the main battery. These are just a couple of quid off of Ebay, and well worth it.
Bedtime reading .........Mercedes Benz E Class and E Class AMG w211 Why is My Battery Not Charging
3.1A Dual Port USB Car Cigarette Phone GPS Charger Lighter Digital LED Voltmeter | eBay

Steve.

 

[smoothcoupe]

Hi,
Simple answer is that your battery readings for both batteries are on a par with mine, so there is nothing to worry about. The more complex answer is that there is a module that splits the charge and tops up the front battery as and when it needs it. I keep a voltage reader in the cigarette lighter permanently, just to keep my eye on the charge in the main battery. These are just a couple of quid off of Ebay, and well worth it.
Bedtime reading .........Mercedes Benz E Class and E Class AMG w211 Why is My Battery Not Charging
3.1A Dual Port USB Car Cigarette Phone GPS Charger Lighter Digital LED Voltmeter | eBay

Steve.

Thank mate.

 

[smoothcoupe]

Hi,
Simple answer is that your battery readings for both batteries are on a par with mine, so there is nothing to worry about. The more complex answer is that there is a module that splits the charge and tops up the front battery as and when it needs it. I keep a voltage reader in the cigarette lighter permanently, just to keep my eye on the charge in the main battery. These are just a couple of quid off of Ebay, and well worth it.
Bedtime reading .........Mercedes Benz E Class and E Class AMG w211 Why is My Battery Not Charging
3.1A Dual Port USB Car Cigarette Phone GPS Charger Lighter Digital LED Voltmeter | eBay

Steve.

Just ordered one... nice one thanks