Backpack sized off-roader?

Originally Posted by Finnster

To me it sounds like the battery is crap. It could be dropping to a low voltage and causing drop outs in the rx. Would explain the weak servo and low power output.

Are you sure you are running them in series? That's ~12-14V+
If that's true, you may have other problems...

Yup, the video was done in series. I have tried a single pack and two in parallel, all with the same result.

Both batteries are pretty much fully charged.