Mighty Mule Gate Opener Replacement Transformer (RB570) This 18 Volt transformer provides a constant charge of power to the gate opener battery through the control board. Used to maintain a battery charge by providing a trickle charge of power to the gate opener battery. Easy DIY (do it yourself) installation or replacement For additional power options, Mighty Mule offers the 5-Watt solar panel kit (FM121) or the 10-Watt solar panel kit (FM123) as a replacement power source. Backed by a 12 month Mighty Mule warranty and Technical Support.