[ujiro]

First check that you actually charged the battery. I did this several times and caused frustration, realizing that I just needed to charge the battery.
That is a small battery though, and I can imagine with hi-speed gears, which don't get the same torque as a standard or torque up gear set, coupled with that heavy spring (that is very heavy for high rate of fire / high speed gear sets!) is causing you problems. I would recommend trying a larger battery, but first ensuring that you charged this battery