Any work inside the system should always be preceded by disconnecting the battery inside the system.  
I'm removing the single factory-supplied DSS (512GB) from my XPS 15 9520 and replacing it with two 1TB DSS's.  Other than my personal safety and the safety of other components in the laptop, is there any reason to disconnect the battery before making the swap?  Thanks in advance. (I've already made a Recovery Drive.)
Disconnect Battery When Swapping DSS?