I just installed a JVC radio in my ELECTRIC Atomic cart. I get really loud motor feedback through the speakers that intensifies with motor speed. I guess it needs a filter of some type but I have no idea.
To determine if the interference is coming in through the power wire try this. Remove the power wire and connect it to a separate 12 volt battery, like a booster pack. If the interference continues, a power line filter will not help. Check for ground loops or bad grounding points.