I am planning my RV-10 electrical system and am considering the Z-10/8 system with the VPX.
Z10/8 Diagram:
http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/Z10-8A1.pdf
http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/Z10-8A2.pdf
My criteria are as follows:
-Generally easy to operate and maintain
-IFR capable with sufficient reliability and backup
-Standard IO-540 with magnetos
-Main battery capacity 17AH or possibly larger PC925 28AH
-Ability to keep EFIS & GPS up during engine start using smaller Aux battery ~7AH
-Do not want full blown two battery setup with cross feed contactors such as Z-14
-Small Aux alternator to run critical items. Helps ensure sufficient endurance if battery capacity is less than expected.
-Alternate path for critical items to battery in case of master contactor or VPX failure
-Ability to use capacity of both batteries for endurance operation
-Backup battery capability for critical items, but not planning for additional 'backup battery' such as TCW IBBS
Endurance bus ( critical avionics for enroute IFR operation ) : EFIS PFD, AHRS, IFR GPS, COM 1, AutoPilot, possibly Xpndr
The VPX installation shows dedicated switched & fused circuits connected directly to the battery. During a failure situation I do not like the idea of flipping several switches to bring critical items back online. There is enough going on in a failure situation - recognizing low voltage condition, managing the alternators, master, etc. I also do not like the idea of the EFIS and IFR GPS restarting in the process of switching over. I realize the IBBS backup solves this problem and is a great product, but this seems like an overly complex and expensive solution considering a 7AH battery is only $40 and easy to maintain.
My proposed solution is to feed power to critical items from the VPX and endurance bus simultaneously. This would utilize the dual power inputs on many devices. Those without dual power inputs can utilize diodes to isolate power inputs. Essentially the backup circuits would always be on during normal operations ( alternate feed active). This means if the master contactor and/or VPX failed there would be no resetting of critical avionics. The VPX recommended backup circuits show switches because of the direct battery connection. My proposal should not require switches as both buses are completely off when master and alternate feeds are shut off. Both the master contactor and alternate feed relay would have to fail before the endurance bus loses power. This seems like an acceptable risk to me.
Here is a crude diagram showing how this would be accomplished:
Comments and suggestion are appreciated. I have quite a bit of time before I have to 'commit' to an electrical design. My goal is to confirm that this is a sufficiently robust/sane proposal based on my criteria and/or if I am missing anything important.
Short of a complete meltdown of one of the batteries I think most SINGLE failures have an acceptable backup. In this design the batteries are
paralleled except during engine crank. Is there any value in adding an additional switch for manually controlling the brownout relay and isolating the batteries?
Normal Operation:
Turn on E-Bus Alternate feed switch before engine start to power up EFIS, GPS
When ready to start:
Turn on Master
Start Engine - batteries are isolated during start by brownout relay
Failure modes:
-Main Alternator Failure
Turn off master - for endurance operation, Pull Alternator field breaker
Turn on Aux Alternator
E-Bus Alternate feed should already be on
Final approach:
Turn on master
-VPX failure
Only devices connected to Ebus are operable
Ebus fed by batteries and main alternator or aux alternator
-Master contactor failure
Only devices connected to Ebus are operable
NOTE: Aux alternator is connected to battery side of contactor
Ebus fed by batteries and aux alternator, main alternator off (unstable without battery)
-Brownout relay failure
Normal power distribution by VPX
Batteries are isolated
Thanks for your input.
-Brendon Van Thomme
Z10/8 Diagram:
http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/Z10-8A1.pdf
http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/Z10-8A2.pdf
My criteria are as follows:
-Generally easy to operate and maintain
-IFR capable with sufficient reliability and backup
-Standard IO-540 with magnetos
-Main battery capacity 17AH or possibly larger PC925 28AH
-Ability to keep EFIS & GPS up during engine start using smaller Aux battery ~7AH
-Do not want full blown two battery setup with cross feed contactors such as Z-14
-Small Aux alternator to run critical items. Helps ensure sufficient endurance if battery capacity is less than expected.
-Alternate path for critical items to battery in case of master contactor or VPX failure
-Ability to use capacity of both batteries for endurance operation
-Backup battery capability for critical items, but not planning for additional 'backup battery' such as TCW IBBS
Endurance bus ( critical avionics for enroute IFR operation ) : EFIS PFD, AHRS, IFR GPS, COM 1, AutoPilot, possibly Xpndr
The VPX installation shows dedicated switched & fused circuits connected directly to the battery. During a failure situation I do not like the idea of flipping several switches to bring critical items back online. There is enough going on in a failure situation - recognizing low voltage condition, managing the alternators, master, etc. I also do not like the idea of the EFIS and IFR GPS restarting in the process of switching over. I realize the IBBS backup solves this problem and is a great product, but this seems like an overly complex and expensive solution considering a 7AH battery is only $40 and easy to maintain.
My proposed solution is to feed power to critical items from the VPX and endurance bus simultaneously. This would utilize the dual power inputs on many devices. Those without dual power inputs can utilize diodes to isolate power inputs. Essentially the backup circuits would always be on during normal operations ( alternate feed active). This means if the master contactor and/or VPX failed there would be no resetting of critical avionics. The VPX recommended backup circuits show switches because of the direct battery connection. My proposal should not require switches as both buses are completely off when master and alternate feeds are shut off. Both the master contactor and alternate feed relay would have to fail before the endurance bus loses power. This seems like an acceptable risk to me.
Here is a crude diagram showing how this would be accomplished:
Comments and suggestion are appreciated. I have quite a bit of time before I have to 'commit' to an electrical design. My goal is to confirm that this is a sufficiently robust/sane proposal based on my criteria and/or if I am missing anything important.
Short of a complete meltdown of one of the batteries I think most SINGLE failures have an acceptable backup. In this design the batteries are
paralleled except during engine crank. Is there any value in adding an additional switch for manually controlling the brownout relay and isolating the batteries?
Normal Operation:
Turn on E-Bus Alternate feed switch before engine start to power up EFIS, GPS
When ready to start:
Turn on Master
Start Engine - batteries are isolated during start by brownout relay
Failure modes:
-Main Alternator Failure
Turn off master - for endurance operation, Pull Alternator field breaker
Turn on Aux Alternator
E-Bus Alternate feed should already be on
Final approach:
Turn on master
-VPX failure
Only devices connected to Ebus are operable
Ebus fed by batteries and main alternator or aux alternator
-Master contactor failure
Only devices connected to Ebus are operable
NOTE: Aux alternator is connected to battery side of contactor
Ebus fed by batteries and aux alternator, main alternator off (unstable without battery)
-Brownout relay failure
Normal power distribution by VPX
Batteries are isolated
Thanks for your input.
-Brendon Van Thomme
Last edited:
