REFLECTOR: 24 volt electrical system

[Ron Brown]

Message
That is the nice thing about building your own airplane - you get to make all of these decisions for your own preferences.  As Chuck points out, Bob Nuckols makes good points about the claimed weight savings and supposed economy of the 24 volt systems.  Bob's responses are very much worth reading - and I believe he has much more experience with OBAM's and airplanes than Greg has.  But both are worth reading!  

I'll also add some real world experience about 12 volt battery capacity - I had the alternator field wire break on a flight from Atlanta to Ft Myers.  I knew I had plenty of capacity but didn't push the issue, so I shut down my strobes, Garmin 430, and auto pilot which are the biggest loads on my plane (well the Nav lights, pitot heat and landing lights are even more but these aren't daylight cruise loads).  

I had plenty of power (still reading 12 volts when I got to Ft Myers) to turn the 430 back on, put the gear down, and communicate.  I fixed the field wire (be sure to double crimp those insulated crimp connectors or use shrink to minimize the vibrating wires!).  It also started the next morning without having to recharge the battery.

When I got home, I made sure to run a load test - over 4 hours with everything on except lights and the autopilot.  Voltage at the end of the test was 11.8 volts and everything was still working fine.  I am using a big ole car battery ($65 for a 72 month battery) from AutoZone.  Always cranks even after sitting in the hangar for a month.  I changed out the original battery after 3 years, took it to AutoZone to have it tested just for my information and it was still generating rated ampacity.  So I have no qualms at all about ole low tech auto batteries....  and you can buy them anywhere, 24-7.

So roll your own for the plane you are building!!!!

Ronnie Brown
N713MR - 173 Elite RG
http://home.sprintmail.com/~romott/page10.html 

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