Access To Auxiliary Battery

The two 12v batteries are being replaced under warranty next week on my DS4 E Tense.

I’ve been back and fore the dealership for months saying that I think the issues with my car is the 12v batteries, they’ve now decided to change both.
I might be a bit cynical but I want to make sure the do actually change both batteries.
The main one under bonnet will be easy to see if its been changed but the internal auxiliary is hidden under the center armrest, how is this removed to access the battery ?

Has anyone done this ?

I have worked out how to access the internal 12v auxiliary battery, it’s actually very simple.
Remove the rubber mat inside the armrest compartment, then push the 4 tabs together and lift out the battery cover.

I’m not actually sure what type of battery it is.
I’ve read that a VRLA battery can be 3 different types .