Drain your eReader's battery as much as possible before starting your repair. Ideally, it should be fully discharged.

Optionally, to drain the battery faster, navigate to More → Settings → Energy saving and privacy and set Automatically go to sleep after and Automatically power off after to Never.

When working on or near the battery, don't use sharp metal tools to avoid puncturing and shorting the battery.

Unplug all cables and fully shut down your eReader.

Your screen should be black and say Powered off.