DEC695 looses time on power outage

[9axqe]

When the server reboots, time is kept, but on power outage (5min), it looses time.

This is problematic for me because I have DNS over HTTPS setup, and when the router boots up thinking it's 2022 instead of 2025, all TLS handshakes fail, hence no DNS. And because NTP tries to reach "de.pool.org", it needs DNS. Catch 22.

I have added a couple of IPs to my NTP servers to prevent this from happening again, but I feel the router shouldn't lose the time within 5min, some battery is empty or defective.

Is this issue expected and if not, is there a guide on how to replace the defective battery?