The weight is about 2 pound or so, but since almost all of it is on the ground and not the tank, it affects running time precisely zero. I have found that the weight of any tank has very little affect on running time. My FO P3 runs virtually the same length of time as the JT or KT, the heaviest. I do run 3300 or 3600 batteries in all my tanks, but just one battery. On the tanks that are factory set for two batteries, I eleminate the splitter harness and run one battery. KT will run about 90 minutes of hard combat on one 3600 battery.