Nighthawk M1 too hot?

Hi, I recently removed the battery because it had started to swell, probably because I have been using it as an always plugged in home router, and the Nighthawk was operating weirdly (speeds fluctuating seemingly based on battery temperature, speeds would drop at 55 C and increase at 46-47 C). I am now using it without battery but am getting even higher temperatures (operating temperature up to 75 C when downloading, but it doesn't seem to affect speed). Is this normal? Is it dangerous for the temperature to go that high?