My 3DS XL is permanently charging even if it's not plugged in

I got this old 3DS XL two months ago, it was working partially good (the only problem was I had to let it charge for 6 hours and the battery only lasted 2 or less hours) but suddenly it stopped working, when connected the orange LED didn't light up and couldn't turn it on no matter what I tried (moving the cable, taking the battery out and put it back again, etc)

I searched for help and the first thing that came up were regular charging port issues (bent pins, dirty port) did everything and it was only temporary, worked as mentioned above but it won't charge and won't turn on again after a while.

And then I searched for help to resolder the charging port, the person who kindly helped me used a heat gun to take it off, change the solder, clean it and put it back. It didn't work at all and what's worst now my 3DS thinks is permanently connected.

Not only the orange LED always lights up as long as the battery has charge, but the home screen shows the charging symbol too. At first I thought it might be the charging port wasn't connected correctly, but even without the whole port it still has the same problem.

Notes:

• I'm aware it might be easier to change the whole board, but I want to try and fix this one before I commit to spend more money on this.
• I don't live in the US so getting replacements or even search a legit place that can repair it is hard, expensive, takes a lot of time and of course, can get scammed (I could get my hands on a new charging port even tho it ended up being a 3DS port, I know they are compatible and work the same but yeah the site said 3DS xl)
• I leave the console for almost a month until my replacements came. While opening and taking the battery out I noticed it was puffed.
• I don't have any experience repairing any electronic device, so I don't really know the name of anything inside the console
• The side pins used in a charging cradle work fine