S211 Auxillary Battery cheap alternative

[ksareen]

Hi all,

I've a 2003 E220 CDI Estate. I replaced the main battery of my car 6 months ago with Advanced 019 AGM Car Battery 95ah 900cca with 5yr Warranty. I think the original was 70Ah.

For the last 2 days since weather has turned colder, the error message "Convenience features not available" has been showing up for the first 4-5 miles of the journey.

The battery voltage in the IPC before crank is 11.5V. After the car starts, the voltage is 13.8V and subsequently 14.0V when the convenience features are available again.

Am I right in thinking that this may be caused by the aux battery which is probably as old as the car or could it be Faulty Isolation Relay draining the main battery?

I am probably going to keep the car for another year max, so can I replace the aux with a Motorbike Gel Battery with same spec/ dimensions like this:
ULTRAMAX YTX14-BS, 12V 12AH 180 CCA MOTORCYCLE, MOTORBIKE, QUAD BIKE, JET SKI

Thanks for your help in advance.

 

[whitenemesis]

The Aux battery only comes into circuit if the main battery voltage is low. It has no influence on starting or Convenience functions.

The Aux battery is cheap enough from the dealership.

 

[190]

I can vouch for the quality of Ultramax batteries as I have run a 20AH Ultramax in my motorcycle for several years. I think you'll find it's an AGM/GEL hybrid battery which is a relatively new type of construction. The reason I mention it is don't get spooked by stories of GEL batteries being damaged by a charging voltage much above 14.0 volts. These hybrid batteries accept the same charge voltage as an AGM in other words 14.5 -14.7 volts.

 

[ksareen]

Hi,
I've just bought a CTEK 5.0 to charge the battery as advised by the vendor of new battery.

Can someone advise if I need to remove the batteries from the car one by one OR can I simply connect to the power points (+ve & -ve) under the hood and both batteries will get charged from there?
Thanks.

 

[190]

It should say in the MB owners manual that you can charge in situ provided the charge voltage doesn't exceed 14.6 volts. Not sure if that will charge the auxiliary battery though.

 

[whitenemesis]

I put my W219 on trickle charge without removing the battery. In fact I had MB fit a Ctek convenience connection directly to the system battery, so I just plug the charger in the boot.

The AUX battery will not charge unless you physically connect the charger to it

 

[ksareen]

I put my W219 on trickle charge without removing the battery. In fact I had MB fit a Ctek convenience connection directly to the system battery, so I just plug the charger in the boot.

So I can connect to the 2 jump start points under the hood directly to charge the main battery?

The AUX battery will not charge unless you physically connect the charger to it

Can I still use the car after removing the aux battery for charging (and isloating/ taping the connectors)?

 

[whitenemesis]

I would connect directly to the battery terminals.

Pretty sure the car will throw errors if you remove the AUX and try and drive it...