Well, I took the risk and tried the 6v battery and connected the dmd unit directly to the motors. I ran the system for 20 min. with no problems. Initially, I tried using the "Y" cable set-up with a separate mixer but for some reason the dmd "did not like it", it was behaving eratically. True, the test run was under no load. The SCR's didn't even get warm and there was plenty of torque. I tried a 5A fuse between the dmd and motor and it was blown, then a 10A and it was fine. As a precaution, I added an extra heat-sink to the SCR's on the dmd unit.