Hella Marine Battery Switch Spare Key Master. These Power Tool Accessories by Hella Marine are specifically designed for use with the 150A Master Battery Switch so you can keep that crucial component of your boat operating system. Please note that when you remove this key from the switch it will cause a short so be sure to place it in the OFF position with the switch off. Add this Hella Marine Master Battery Switch 150A Key to your toolbox today for a more efficient way to power your marine devices. Specifications for Hella Marine Master Battery Switch Spare Key: Manufacturer: Hella Marine Color: Black Package Contents: Hella Marine Master Battery Switch Spare Key Hella Marine 706729011: Battery Switch Spare Key Master