i have the 4.5 on 2s and the 5.5 is a lrp which on there site says 7-11 volts i had a ballistic 5.5 in my jammin scrt ran it on 3s from the day it came out to the day the sc10 4x4 came out. never had one problem. as far as the lrp goes i had the 4.5 in my sc10 lasted three packs on seven volts. the rotor magnet spun on the shaft i sent it back two months ago called ae monday had them swap it for the 5.5 thanks for the warning