my xbox one controller melted, how or why ?

Hello, first it's a pleasure to be able to help you today.

My name is welcome to the community.

Hello Devin, you mention that the batteries were very old, if the pilahs you were using are not alkaline they will leak the liquid from the batteries, this happens when the battery is not alkaline and are long in an equipment.

It's impossible to say for sure, but often that's caused by some kind of short, which can cause either a battery or a component on the circuit board inside the controller to get really hot.

Typically if a battery leaks, it will just cause corrosion, and you'll usually see evidence of that inside the battery compartment, on the battery contacts.

I would try and get through to Xbox support about this, because sometimes companies will get you to send in the faulty product so they can investigate the cause of the damage. If it's under warranty, they will send you a replacement controller, but if it's not you'd need to buy a new one. Definitely do not try and use that one again, and if there's still batteries in it, take them out.

Batteries are xbox original rechargeable battery

weird how that happened and not being plugged in or on, what batteries are you using in the controller, that also looks like it has melted from the outside as the d pad is distorted and that has a seperate plastic section
underneath. and in the picture the other plastic beneath is not melted so look like it was external heat, where is it stored.

if
that was the case, wouldn't the xbox and other controller be damaged too as this is where it has been since last use?