Thats a 50watt charger if I'm not mistaken so you realize its going to limit charge current when you charge a 4S? Instead of 5amps, you'll see current like 3.4a at 14.8v and a little less than 3a at 16.8v. It will charge a 4S (rated to 6S) but these higher cell counts will take a while due to reduced charge current.

I see people getting surprised when they get a 50watt charger and don't know charger will limit charge current to stay under its 50watt power output.