Put in new batteries a year ago. show full charge, but unit goes from green to yellow to red in 1/2 hour or so. Charger goes full charge and then goes to zero in 1/2 hour. Have tried charging batteries indiviually with 12 volt charger. Batteries plus says batteries are good. So what is problem. User was left stranded in Disney 2 weeks ago. If controller, where do you get and any idea of cost.