Same thing happened to me after using my weed trimmer for about 20 minutes with the XC battery it came with. I called Milwaukee and they said they know this is an issue but not as big as the internet is making it out to be… unreal. Anyways I exchanged it at Home Depot for now but may have to just return it and switch brands altogether… would suck as I have plenty of M18 batteries but don’t want to risk melting them.