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Stay InspiredEAA is your guide to getting the most out of the world of flight and giving your passion room to grow.
Builder’s Tip Battery Disconnect
By Thom Riddle, Buffalo, New York, Thatcher CX4 (N254RM)
October 2016 - I don’t have the problem of the battery running down on my current airplane (Thatcher CX4), but I have had it on previous airplanes.
I’ve solved the phantom-load problem by wiring into the negative battery line (the one going from the battery to ground bus or airframe), a high amperage manual shut-off switch. Locate it in a convenient location easily accessible without removing engine cowl, still trying to keep the large gauge wire as short as possible. The ones I’ve used in the past have a “key,” which is removed when the circuit is open.
Example of a keyed battery cut-off switch for under $20
A shut-off switch solves more than just the phantom-load problem. It also provides an extra bit of security to discourage vandals and thieves, but more importantly for me is that I like the battery ground to be disconnected whenever I'm doing any kind of work on the engine. This eliminates the need to actually disconnect the negative battery terminal.