Ditto the suggestion of chasing the amps to figure out where your major current draw is coming from. If you have a philosophical objection to Craftsmen, here's the
Northern Tool version. I personally have a
Klein CL2000 for work since I get to deal with lot of amps with funky waveforms on our welding equipment.
At any rate, figure out what's drawing all that current first. Then you can start checking for big voltage drops going into that motor. Just set your multimeter to DC Volts, clamp a lead on a motor terminal, and start working your way back along that wire to motor controller, touching your other lead anywhere there's bare metal to touch. If you see a big jump in volts from one point to another, you know there's a large resistance there where you're losing lots of power.
Also, if the problem does turn out to be your BaneBots 64:1, and you're running that with an RS-550, or one of the Fisher Price motors, consider switching to a higher torque motor. Specifically, either the BaneBots RS-775-12 or RS-775-18. Either of those motors is going to give you more torque per Amp than the RS-550. Mind you, both of them have a lower free-speed than the RS-550, so your system is likely to run some what slower. But at least it won't be completely draining your battery, right? Just make sure to look out for case shorts on the RS-775-18, as they're notorious for that.