Lag in Games with Charging

So I recently started playing Star Wars Fallen Order with a laptop under the minimum specs. I boot it up and I see a lot of lagging even in Low settings. I turn up my settings to Medium and I disconnect my Charger which I was using and the game was running smoothly in Medium Settings with very little stuttering. Then I put my charger in and it started stuttering again. Could someone tell me why is this happening and how should I play games because these games drain a lot of battery power and I have to connect the charger. Anything would be appreciated