Rock 3A RTC issue

Hi Team,

I am working on Rock 3 A (8 GB and 128 GB) Ubuntu 20.04 LTS OS (rock-3a-ubuntu-focal-server-arm64-20221101-0219-gpt.img.xz). I’m facing some issues with RTC.

Initially I connected using POE with internet and date, time has been fetched automatically. Later I connected the RTC battery on the module and followed this RTC Setup , and device is powered off.

After sometime (more than 17 mins), I powered on the device without internet connection, the date&time was wrong. Means, it was the time I powered off the device.

So, I checked again but this time less than 17 mins (poweroff time). And then I powered on it’s working fine. The current date and time and device time are correct.

As of my notice, whenever the device powered off more than 17 mins, rtc time is not syncing. Correct me if I am wrong.

Could you please help me with this issue?
Thanks in advance.

Team, waiting for your response.