Secondary battery ML280 2008

[TRINGTRING]

I have a ML280 CDI 2008 and a battery warning is showing .Main battery testing fine as is alternator.
I understand it may be the secondary battery that is the problem but where is it situated in the car ?
Any help would be appreciated.
Thanks Michael

 

[gazz]

Iirc it's in the same hole under the driver's seat alongside the main battery. I think you'll have to take the main battery out to see it. I noticed mine in there when I replaced the main battery.

 

[TRINGTRING]

Thanks for info.
Is it possible it will recharge as it only showed after car had been idle for 2 weeks ?
If not is there any problem if I just ignore the warning,it does not say take to dealer etc.
Michael