The concept is pretty simple: select one of two batteries with the highest voltage and switch it to the load. If the two batteries have the same voltage then both are connected to the load and they will share the load current between them. The voltage drop across the switches should be as low as possible to keep power dissipation, heat, and losses to a minimum. Power to the load can be switched on or off by momentarily placing a magnet near the circuit. This allows the circuit to be completely enclosed within the aircraft fuselage. The current drawn from the batteries while in the off-state mode should be as low as possible . It should take more than one year to discharge the batteries.
Input Voltage Range: 3 - 13V (1S to 3S LiPo batteries)
Max current to load: 5A
Switch Insertion Loss at 5A: 100mV
Off-state Current: <40µA
On-state Current: 5.5mA (almost all of that goes into the LED)
Size: 12 x 22mm (0.48" x 0.87")
Cost: $10.72 for components and PCB.