"Weird, the bottom shell of my new 3DS XL is kinda being pushed out slightly around where the R/ZR buttons are, hey wait a minute, where's the battery on the new 3DS XL again...?" *Checks Google* "****"
I have Samus Returns as a physical copy and I also have enough of a backlog for physical games to fall back on while I wait for a new battery but... There's a reason why I upgraded when I did, My launch 3DS is in real rough shape. That said right now It's the only one I have that I can safely charge (or operate like at all.) since it doesn't have a swollen battery and that's a big deal.
I'm at work right now (I discovered this during my lunch) so I can't try to remove the battery either until I get home. Hopefully nothing else is damaged. A week or two with old reliable here is bad enough.
Edit: I was able to safely remove the battery. The battery cover will need to be replaced because the expanding battery wound up causing problems but otherwise the system is undamaged.