RE: Jet Cat help!!
Hi Ted,
I would take particular note of Oliver's comments. That cable should have no influence on your ecu battery voltage. I would bet you have a dodgy NIMh battery pack. They are infamous for false peaking during charging because of their relatively high internal impedance. I never use them in aircraft for that reason. I only use them in rc cars and even then they are a pain.
I would remove that pack from your jet until you test it more. Is it a new pack?
Craig.