Return it and buy a new one. Sometimes saving a few bucks isn’t worth it.
First suggestion - RMA it
Second suggestion, if you wanna try to fix it yourself either in the meantime or before RMA:
- Play games on it until it completely runs out of charge
- Launch into the bios until it completely runs out of charge
- Repeat the above until it no longer turns on
- Plug in your Steam Deck. If it turns on automatically, repeat the above two steps until it doesn’t when you plug it in
- Leave it charging and turned off for 6-8 hours, preferably overnight, then turn it on and check again
If you’re back up to 95%+ then it’s a battery calibration problem which most are
Try to recalibrate the battery. Enter battery storage mode https://help.steampowered.com/en/faqs/view/69E3-14AF-9764-4C28 and then do a full charge/discharge cycle.
If that doesn’t help, go to UEFI setup and keep this screen open until the battery runs out.
If that also doesn’t help, then contact Valve support to arrange RMA.
I’m clearly not the manufacturer. Contact them.
Give it a 5-6 full charge-discharge cycles and see if it corrects itself. Play it for few hours and then let it charge overnight or something. Both my brand new decks had 50ish% battery life at first, but it corrected itself after a few charge cycles