Given the context of the picture, I'm going to go out on a limb and say it's most likely the switch. Besides, the MMM's fan works poorly with duck feathers stuck in the blades.
“The modern astrophysical concept that ascribes the sun’s energy to thermonuclear reactions deep in the solar interior is contradicted by nearly every observable aspect of the sun.” —Ralph E. Juergens
If your using bullet connectors, which the picture sort of resembles, just plug one batts negative into the others positive and do away with that little in between wire thing. Unless your running this in something like an E-Revo, than an extension may be needed.