only one battery connecting to hv maxx??

[LEX]

hiya,
i just went to have a run with my emaxx, and it seems only 1 battery is gettting through, it was going really slow with the batts at peak so i checked the esc by hooking up one plug to a batt, it worked, then the other and it didnt, so 1 plug on the esc isnt getting power, and i checked it on numerous batteries so its not them, whats wrong?
thanks,
alex