An employee was preparing to perform a load test on a battery system. He was receiving directions over the phone from the lead supervising technician. He and his co-worker were attempting to divide the 240-volt battery system into two 120-volt systems to perform the load test. His supervisor was directing them on where to divide the battery string. The system was then divided at cell 56 instead of cell 58. He was attempting to move the battery strap when the battery connector was placed on the terminal post, closing the 240-volt system. This created a short in the system, resulting in a DC arc flash that burned his left hand. Gloves were not worn at the time of the incident.