Hello jstodden;

The only mention of a battery in the HMI Comfort manual is for the support of the real-time clock.

https://support.industry.siemens.com/cs/ca/en/view/49313233/157370799499

Unfortunately, there is no description of this battery replacement procedure.

If that was the battery you were inquiring about, you might need to start a Support request (the link is at the top of this page).

Hope this helps,

Daniel Chartier