nwparkinson(at)btinternet Guest
 
 
 
 
 
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				 Posted: Sun Sep 23, 2018 2:03 pm    Post subject: Fwd: Hello everyone , new here and need some help ! | 
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				 	  | Quote: | 	 		  Hi all 
 Im building an Rv8 and would like to make it IFR with a Garmin g3x fit . 
 
 After reading the excellent online book Aeroelectric Connection i intend to use the system 13/8 with B&C parts . (Attached Diagram ) 
 [img]cid:5AF805CB-E91C-49D7-ACCE-6C7472E00007[/img]
 I however have a few  questions , as my school boy electrics is struggling ! 
 
 1)What happens to an Alternator ( in this case the SD-  when it reaches its max current capacity , does it get hot and eventually blow , or does it just start decreasing its voltage output , eventually going below the battery voltage causing a current drain from the Batt ?
 
 2) If its the former I'm thinking following a Main Alternator  failure if the Aux Alternator  is turned on ( without opening the main battery contactor ) maybe there is room to overload this too ? If so i was thinking maybe an improvement to this system would be an interlock that when the E-Bus and Aux Alt  are  activated they open the ground to the battery contactor coil and thus prevent an overload of the emergency system ? Maybe you could have a guarded 3 posn switch that on first click , opens the main battery contactor and closes the E-Bus Alternate feed , then second click closes the AUX - Alt feed relay ? A one switch saves the day sort of thing ??
 
 3) It would be nice to have a CAS message on my Garmin G3x that indicates if the SD-8 is functioning ok incase of a main failure . Im thinking of a “Standby Alt Fail “ caption that would indicate when ever the SD-8 is not producing power and ready for an emergency . What sort of output would an unloaded ( Supply relay open ) Sd-8 be producing ?  unstable , high , low or on task at 12v?? How can i send a “I'm functioning ok and producing power “ signal ? Maybe a relay coil on its output that closes a signal to the G3X ?? ( see my hand drawing ) 
 [img]cid:8F93CFCE-13D5-444D-93CA-52D11D73DBC6[/img]
 But maybe id need diode after that coil to ensure its only Aux Alt that can close it and not reverse supply ?? What would a Diode in the line do to supply voltage ?? How could i make it so the relay closes at 12ish volts ??
 
 Any better ideas ??
 
 Too many questions I know !
 
 Thank you so much for any help !
 
 Neil 
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