Here's the page with the tech notes.
http://www.gpdealera.com/cgi-bin/wga...pgm?I=FUTM0224
It's a high-current, digital servo. Use 4.8 V ONLY...that's a 4-cell NiCd or NiMH battery pack. More cells or other types of battery packs are not recommended at all.
At idle, or under no load, though, the servo should draw little current, so it may have some kind of difficulty if it's drawing high current under little or no load.