MacBook Pro getting hot and draining battery with light use?

I recently got my hard drive and screen replaced in my 15" MacBook pro from mid 2012. Ever since I got it back, I have noticed the system kind of lagging and the base of my computer getting really hot after using it for about 3 minutes and the fan starts. Also the battery drains rapidly. I am not running a lot of apps when this is happening, at max 3 at a time. My battery report on my mac says it has 448 battery cycles which is normal so I don't know if this is a defunct battery or what? Any thoughts?