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EFIS fuse blown

RV12Pilot

Member
Have a RV-12 with Dynon Skyview Classic.
What would cause the EFIS fuse to blow?
Last Saturday shortly after take off the EFIS fuse blew, got a “Aircraft Power Loss” message and was able to switch to the B/U battery. Returned to airport and landed. About 10 minutes later the B/U battery “died”.
Replaced the B/U battery.

TIA Charlie
 
The same thing happened to a friend of mine. Evidently the 5 amp fuse is OK for normal operations.
But if the Skyview is operated for any length of time on its internal backup battery, that battery runs down.
Then the next time that the plane goes flying, the combined current of the Skyview plus charging the rundown backup
battery is enough to blow the 5 amp fuse. If I remember right, he replaced the 5amp fuse with a 7.5 amp fuse.
 
Running both down is also pretty hard on the Ducati Voltage Regulator, too.


If you can, put the main battery on a 10 amp 14.4V or higher capable battery charger and leave your main switch on, along with the Dynon Skyview, but pull the fuel pump fuse, for 1 to 1.5 hrs.

You want all batteries, both on the plane and the backup battery, as close to fully charged before you start up the engine and let it's charging system operate. Top charging an AGM battery before not using it is very important. They like to be stored with a full charge. I don't shut my motor off until the charging rate at 3000 rpms has dropped down to a 2 amp charge rate or less, before I shut down the motor.
 
Legacy 12's with Skyview had a 5 amp EFIS fuse. That was changed by Van's sometime around 2016, I think, to a 7.5 amp. The OP doesn't say what rating the blown fuse was, but using a 7.5 is currently approved.

BTW, the backup battery should be good for about an hour in flight. If there is a little exclamation point up in the Skyview header next to the clock then the battery needs to be tested. The test is a built-in feature within the Skyview, and runs about 45 minutes while you have lunch. There is also a yellow caution message, so you really can't miss it.
 
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If the fuse link is silvery black, short.
If sagging and broken too small of a fuse.
If a sharp break circuit overload for short period of time.
 
Running both down is also pretty hard on the Ducati Voltage Regulator, too.
I don't shut my motor off until the charging rate at 3000 rpms has dropped down to a 2 amp charge rate or less, before I shut down the motor.

I have the Odyssey battery. So this is something you’d recommend that I do?
 
Legacy 12's with Skyview had a 5 amp EFIS fuse. That was changed by Van's sometime around 2016, I think, to a 7.5 amp. The OP doesn't say what rating the blown fuse was, but using a 7.5 is currently approved.

BTW, the backup battery should be good for about an hour in flight. If there is a little exclamation point up in the Skyview header next to the clock then the battery needs to be tested. The test is a built-in feature within the Skyview, and runs about 45 minutes while you have lunch. There is also a yellow caution message, so you really can't miss it.

I had a 5 amp fuse. Am getting a 7.5 amp fuse tomorrow and replacing the 5 amp.

I did have the little exclamation point next to the clock for a few flight hours before all of this happened to me (didn’t know what that meant at the time). After the battery “died” I had a faint battery with an X on it next to the clock.
 
If the fuse link is silvery black, short.
If sagging and broken too small of a fuse.
If a sharp break circuit overload for short period of time.

To my untrained eye seems my fuse is a combination of all three. I’ll try to get an A&P to tell me his thoughts tomorrow
 
Most modern voltage converters work as power converter where they have a constant load voltage and given a constant load current there is a constant power required. When the input voltage drops then to supply the same power they require more input current (P=I*V). Therefore during normal operation off of a charged battery you could have been using less current than when you went to the backup battery that had a lower voltage. Most regulators also have an input under-voltage cutout. This is used to protect the current from going too high with this type of converter. This is just a possible scenario but it could explain what you saw.
 
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