[Lyle Swallows]

who's installed a master switch on their ship? my machine came with a physical battery disconnect underneath the passenger seat, i'm wanting to swap it out for a remote electric master relay.
for fault protection and redundancy reasons i still want the alternator to be in parallel so if the battery becomes disconnected in flight the alternator is still producing a charge.

in my head this sounds simple enough, i'm curious who is actually utilizing a master.

[Orv Neisingh]

who's installed a master switch on their ship? my machine came with a physical battery disconnect underneath the passenger seat, i'm wanting to swap it out for a remote electric master relay.
for fault protection and redundancy reasons i still want the alternator to be in parallel so if the battery becomes disconnected in flight the alternator is still producing a charge.

in my head this sounds simple enough, i'm curious who is actually utilizing a master.

One of the 6 ships that I have here has a master switch with a battery disconnect relay. I do not have a wiring diagram for this setup.

[Tim Morris]

I have.  Works great.  Standard continuous duty battery disconnect relay.  Installed the relay near the battery on the battery box.

[Lyle Swallows]

i'm liking the idea of a latching relay which doesnt take any current to keep its state.

i'm wanting to use one for a EarthX lithium battery install and prevent parasitic drains from external regulators like i have heard of. a battery to bus disconnect just makes sense also.

i am mindful of lithium battery BMS's and battery disconnects can surge an alternators current if disconnected from whatever even shuts if off. so there's a few alternator protection devices out there for this use. Balmar makes one specifically for the use of lithium batteries. Balmar APM-12

i'm working on making my own master wiring diagram for my ship and systems.

[Kevin Alderman]

I am an A&P/IA, when I built mine I used a standard continuous duty solenoid mounted on the back of the cockpit just like on a certified aircraft, pax side, just above the battery with a switch in the OH panel. From here it goes to the main bus for the overhead as well as the main forward avionics bus for the pedestal, the starter wire is also attached to the cold side of the solenoid so that if the master is off, no chance of the starter moving the blades in the shop.

Wiring is easy- the positive goes from a ring terminal on the hot side to one terminal on the solenoid, the other small terminal goes to a toggle overhead that then connects to ground. The switch connects the circuit to ground thus energizing the solenoid.

KA

[Lyle Swallows]

A&P here aswell which is why i think it's prudent to have a properly designed system.

i was planning to have the starter power lead direct to battery and just the starter solenoid/relay is switched by the button and key and master relay, however i could see an inadvertent arc coudl take place spinning engine and blades..

i would be concerned with the starter amperage/current draw damaging the master relay however. the relay i am planning to use is only 100amp continuous latching.

i went with latching because it requires no power to hold its on state, only momentary power to change states from on to off. if a sudden voltage spike/drop occurs i didnt want the master relay to drop out, further spiking the alternator and remaining electrical system.

[Kevin Alderman]

As someone that has flown many experimentals for the original builders- i.e. first flight- with the sometimes expected results of unintentional landings, I always want a way to completely disconnect the power as close to the battery as possible before I hit the ground to limit the chances of a post landing/crash fire. 
This was me 2 weeks ago. The engine came apart in flight. First flight, no I didn't build it. No airframe damage, she does need an engine and prop and new gear bungees. No post crash fire. Just before landing I switched off the master and the fuel. Me? Not a scratch. The G meter read 1.2Gs after landing. Was a 3 pointer, but the field was so soft that the gear did a split as I rolled to a stop. 




KA

[Jared Hartzell]

@Kevin Alderman Wow Kevin, glad you're okay! Great job!

[Lyle Swallows]

a very wise lesson. everything we do should be with safety in mind. very glad you were able to get that down in one piece! yes removing any unintentional ignition source is such a good mindset to have if things go south.

thanks for your input kevin!

[Orv Neisingh]

Very nice safe landing in a confined space for sure, good job!