Do DeWalt charging safety features reside in a dewalt charger or a dewalt battery?
Although product recommendation requests usually get closed on this site I have a couple of comments to make. 

First off you should be aware that you pictured DeWalt's 20V Flex  Battery technology. Yet you showed a DeWalt charger that is designed for a different 18V setup. You need to be very careful to not mix up technologies. Use the correct manufacturers chargers.

Secondly you should not use some off the wall third party chargers with power tool batteries. Every manufacturer has their own design for their battery technologies designed to be used with the chargers designed/specified by the manufacturer. In this regard taking ideas like this off U-Tube videos is ill advised. I'll repeat myself "Use the correct manufacturers chargers".