Auxiliary battery? Fix or ignore?

[myothercarsakart]

It's an ML350, drives fine. But anyone else had the auxiliary battery warning come up on the dash/display? Merc garage quoted £400 to replace but the chap didn't know what the auxiliary battery even does. Manual doesn't have any info. I'm thinking of just ignoring it.

[.richard]

Have Eclass which showed same message. Stop start and hold both malfunctioned. Quote for new battery from internet price matched by Merc dealer. Fixed for £80. Hold an excellent feature.

[595Heaven]

There are a few YouTube vids showing how to change it. Looks fiddly, but pretty straightforward. As an example https://youtu.be/A9XaApSoAAw

Example battery here: https://www.amazon.co.uk/dp/B06X3R3MPT

You’d need to check figment for your car...