RJJM

Thanks for any assistance. If I do not drive my car for a week or so I get a message that states Auxiliary Battery Malfunction. Most times it goes away after an afternoon of driving.Today it did not. Will the trickle battery that came with the car solve the issue? Or does that only support the main battery? How long should that auxiliary battery last? Its a 2017 with 19,000 miles. Any intel would be appreciated.

Vladimir_S63

Got the same message on my 2018 S400d sedan with 120 k km. It was replaced in the service for about 200 EUR.

Heisenberg

In S63 it is actually a capacitor, not a battery - but M-B calls it a 'battery' so they can dodge extended/CPO warranty coverage on it.

You can buy the part for around $100 but I believe it requires a M-B computer to match it to the car, so the dealer will nail you for that even if you source the part at cost. I was charged around $500 for the part and labor by my dealer on my 2015 before I traded it in, and wasn't thrilled about it.

RJJM

Thanks for the information!!

dasonen

Indeed - it's set of supercapacitors.

No, there is no need to use a computer to match part with the car.
If you know how to solder electronics - you can order supercapacitors for few $ and replacem them by yourself.

JimWilder

Trying to find that in WIS to replace mine, but nothing comes up. Can you give me a hint on where to look?

noobified

Nvm.

LSwitty

I’m waiting for the dealership to get back to me.

they have been terrible at debugging the issues with this car.

happy to have found some other posts with the same error. Looking for what you had fixed that solved the problem?

thanks!

Quadrobenz

MB definitely calls it an Aux Battery, at least in the S65. I had it replaced about 3 months ago in my 2017 S65 Cabriolet. The symptoms were random accessory malfunction and Inop messages on startup. Replacing the Aux Battery solved it.

haa

I was told it was under the rear passenger side seat in the cabriolet as oposed to the trunk. Was that the case with your S65 Cabriolet?

Quadrobenz

I did not ask where it was, not my typical behavior. I would doubt it is trunk accessible in the S65 Cab, too many things in the way with the top well and mechanisms. There is no space under the trunk floor in an S65 Cab because the standard Burmester 3D subwoofer completely fills the space.

okbarnett

try looking on youtube. i think its in the right rear side floor behind the wheel well