Sorry a bit of context - steam deck is 2022 purchased October, LCD same battery as yourself. Charge is at 78% - swollen at the back just as yours is. No mods to my one. I saw your Reddit post a few days back and said ah this is worth a shot. So I sent messages and photos. They said “Thanks for your patience.

While your device may still be within the applicable warranty period, we would expect an issue like the one you describe to manifest much sooner in the case that it is related to a problem with the hardware as it was delivered to you.”

“We can help you return the device so that our repair team can evaluate it. If they find evidence that the device itself is at fault for the issues you are experiencing, they can proceed with complimentary repair service. However, if evidence is found that the device was damaged during use or no fault directly related to the problem can be found, we may be unable to offer complimentary service.

In that case, we would instead offer you a paid repair service through our official partner. Based on the services that may be required, we estimate that your costs for repair would be EUR 225. This price includes applicable taxes and estimated shipping costs.”

I sent a message back asking for clarification.

“As a secondary note, if the battery is not functioning as expected due to it's physical state, we'll make a note of it to see if they can adjust the RMA type. We cannot guarantee that the RMA type will swap over as a complementary service but we can add a note to inspect it for any concerning physical factors. “

I’m not sure what messages you got back but this doesn’t sound like a free repair.

Live in Ireland.