Yes, you can safely use 6.0 Volt batteries for powering Hitec receivers (and other brand receivers). I'm using 6.0 Volts on all my receivers, which are all Hitec at the moment. As far as I know, all of the popular receivers from the major brands are capable of being run on either 4.8 or 6.0 Volts. It will provide more torque for the servos, better holding power, and faster response time, but a 6.0 Volt pack of the same capacity of a 4.8 V one will drain a little faster, so be sure to compensate. Hope this helps!