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Z-19 and multiple busses

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corey.crawford(at)gmail.c
Guest

Posted: Mon Feb 18, 2008 4:35 pm Post subject: Z-19 and multiple busses

Hello,



I'm looking to use the Z-19 drawings to create the electrical system to power my electrically-dependent Subaru engine and had a question:



Is there a reason I shouldn't go with a single engine bus that's fed by both batteries, with diodes to prevent a bad battery from sucking in all the juice?

 

The Z-19's show one bus per battery and then using a diode bridge for each component - this would move the diodes between the battery and the bus, instead of being placed between the bus(ses) and the individual components.

 

Comments?



-- 

Corey Crawford  [quote][b]

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nuckolls.bob(at)cox.net
Guest

Posted: Mon Feb 18, 2008 5:35 pm Post subject: Z-19 and multiple busses

At 05:26 PM 2/18/2008 -0700, you wrote:



 	  Quote: 	
		  Hello,



I'm looking to use the Z-19 drawings to create the electrical system to 

power my electrically-dependent Subaru engine and had a question:



Is there a reason I shouldn't go with a single engine bus that's fed by 

both batteries, with diodes to prevent a bad battery from sucking in all 

the juice?


	


   Batteries don't go bad in ways that "suck juice".

   I presume that since your airplane is decidedly

   dependent on 100.0% availability of power, you'll

   not only use modern, RG batteries . . . you'll make

   at least some effort to see that they're discarded

   for lack of capacity . . . which will happen long

   before they don't crank the engine.



 	  Quote: 	
		  The Z-19's show one bus per battery and then using a diode bridge for each 

component - this would move the diodes between the battery and the bus, 

instead of being placed between the bus(ses) and the individual components.


	


   The dual diodes are intended to isolate a battery

   with higher state of charge from being tapped by

   the equipment that has reduced the other battery

   to a lower state of charge. It's not batteries that

   are the energy thieves . . . it's stuff you have

   turned on.



   Bob . . .

        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

        ----------------------------------------

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corey.crawford(at)gmail.c
Guest

Posted: Mon Feb 18, 2008 6:12 pm Post subject: Z-19 and multiple busses

On Feb 18, 2008 6:32 PM, Robert L. Nuckolls, III <nuckolls.bob(at)cox.net (nuckolls.bob(at)cox.net)> wrote:

 	  Quote: 	
		      The dual diodes are intended to isolate a battery

   with higher state of charge from being tapped by

   the equipment that has reduced the other battery

   to a lower state of charge. It's not batteries that

    are the energy thieves . . . it's stuff you have

   turned on.

	




I think I got it .. the diodes prevent the Main Battery from being used by components on the Engine Bus and vise versa. If the two busses would feed the exact same components, is there any reason to separate them? The only thing I'd lose is not being able to isolate a battery, or am I missing something? (I'm not sure being able to isolate a single battery is very helpful in this scenario - the whole engine can be isolated with the dc power switch if needed).

 

Thanks! 



-- 

Corey Crawford  [quote][b]

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nuckolls.bob(at)cox.net
Guest

Posted: Mon Feb 18, 2008 8:04 pm Post subject: Z-19 and multiple busses

At 07:09 PM 2/18/2008 -0700, you wrote:



 	  Quote: 	
		  On Feb 18, 2008 6:32 PM, Robert L. Nuckolls, III 

<<mailto:nuckolls.bob(at)cox.net>nuckolls.bob(at)cox.net> wrote:

>   The dual diodes are intended to isolate a battery

>   with higher state of charge from being tapped by

>   the equipment that has reduced the other battery

>   to a lower state of charge. It's not batteries that

>   are the energy thieves . . . it's stuff you have

>   turned on.



I think I got it .. the diodes prevent the Main Battery from being used by 

components on the Engine Bus and vise versa. If the two busses would feed 

the exact same components, is there any reason to separate them? The only 

thing I'd lose is not being able to isolate a battery, or am I missing 

something? (I'm not sure being able to isolate a single battery is very 

helpful in this scenario - the whole engine can be isolated with the dc 

power switch if needed).


	


   I'm not sure about your desire to "isolate a

   battery". When the alternator quits, the

   energy available is finite and contained totally

   within the battery(ies).



   When the low volts warning light comes on, wiring

   per Z-19 requires no action on the part of the

   pilot except to close the endurance bus alternate

   feed switch and open both battery master switches.

   Then make preparations for a no-alternator

   en-route phase of flight followed by approach to

   comfortable landing. Once your comfortable landing

   is assured (short final over the numbers) close

   the master relays and run as much "stuff" as you

   like to complete the flight.



   Normal operations are with the primary engine

   power switch ON and the secondary  switch off.

   Assuming you've done your homework and have

   a considered preventative maintenance program

   for batteries, then you KNOW how long you

   can operate battery only in the endurance

   mode. If you have not done your homework and

   find that the engine is not running well for

   as long as you anticipated, you may have

   to close the secondary power switch to allow

   the main battery to support the engine. If

   the engine battery's lack of capacity proves

   to be a surprise, then the main battery's true

   condition is probably a mystery too . . . it's

   time to call it an emergency.



   The design goal is to minimize in-flight

   diagnostics, switch flipping and other

   distractions that prevent you from doing

   your best as a pilot. With a modicum of

   planning it's a no-sweat deal.



   Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

        ----------------------------------------

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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corey.crawford(at)gmail.c
Guest

Posted: Tue Feb 19, 2008 8:06 am Post subject: Z-19 and multiple busses

Thanks for setting me straight. I was under the impression that normal operation would see both engine power switches on.



 - Corey



On Feb 18, 2008 9:00 PM, Robert L. Nuckolls, III <nuckolls.bob(at)cox.net (nuckolls.bob(at)cox.net)> wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)cox.net (nuckolls.bob(at)cox.net)>

 

At 07:09 PM 2/18/2008 -0700, you wrote:



 	  Quote: 	
		  On Feb 18, 2008 6:32 PM, Robert L. Nuckolls, III


	




 	  Quote: 	
		  <<mailto:nuckolls.bob(at)cox.net (nuckolls.bob(at)cox.net)>nuckolls.bob(at)cox.net (nuckolls.bob(at)cox.net)> wrote:

 >>   The dual diodes are intended to isolate a battery
	


 	  Quote: 	
		  >   with higher state of charge from being tapped by

>   the equipment that has reduced the other battery

>   to a lower state of charge. It's not batteries that

 >>   are the energy thieves . . . it's stuff you have
	


 	  Quote: 	
		  >   turned on.



I think I got it .. the diodes prevent the Main Battery from being used by

components on the Engine Bus and vise versa. If the two busses would feed

 >the exact same components, is there any reason to separate them? The only
	


 	  Quote: 	
		  thing I'd lose is not being able to isolate a battery, or am I missing

something? (I'm not sure being able to isolate a single battery is very

 >helpful in this scenario - the whole engine can be isolated with the dc
	


 	  Quote: 	
		  power switch if needed).


	


   I'm not sure about your desire to "isolate a

   battery". When the alternator quits, the

    energy available is finite and contained totally

   within the battery(ies).



   When the low volts warning light comes on, wiring

   per Z-19 requires no action on the part of the

   pilot except to close the endurance bus alternate

    feed switch and open both battery master switches.

   Then make preparations for a no-alternator

   en-route phase of flight followed by approach to

   comfortable landing. Once your comfortable landing

   is assured (short final over the numbers) close

    the master relays and run as much "stuff" as you

   like to complete the flight.



   Normal operations are with the primary engine

   power switch ON and the secondary  switch off.

   Assuming you've done your homework and have

    a considered preventative maintenance program

   for batteries, then you KNOW how long you

   can operate battery only in the endurance

   mode. If you have not done your homework and

   find that the engine is not running well for

    as long as you anticipated, you may have

   to close the secondary power switch to allow

   the main battery to support the engine. If

   the engine battery's lack of capacity proves

   to be a surprise, then the main battery's true

    condition is probably a mystery too . . . it's

   time to call it an emergency.



   The design goal is to minimize in-flight

   diagnostics, switch flipping and other

   distractions that prevent you from doing

    your best as a pilot. With a modicum of

   planning it's a no-sweat deal.

   Bob . . .

	


-- 

Corey Crawford  [quote][b]

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

longg(at)pjm.com
Guest

Posted: Tue Feb 19, 2008 8:06 am Post subject: Z-19 and multiple busses

Bob, if I "open both battery master switches" which carry my EFI, ECU

and primary fuel pump, my engine will go putt-putt and die. On the other

hand closing the #2 fuel pump switch will provide power to the #2 fuel

pump from the main bus for my non-running engine. I'm sure you were

referring to a standard aircraft engine and not an electrically

dependent one. For Z-19 to be effective, the EFI/ECU/FP require at least

1 live feed. That source is not provided on the e-bus.



--

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nuckolls.bob(at)cox.net
Guest

Posted: Tue Feb 19, 2008 8:46 am Post subject: Z-19 and multiple busses

At 11:02 AM 2/19/2008 -0500, you wrote:



 	  Quote: 	
		  



Bob, if I "open both battery master switches" which carry my EFI, ECU

and primary fuel pump, my engine will go putt-putt and die. On the other

hand closing the #2 fuel pump switch will provide power to the #2 fuel

pump from the main bus for my non-running engine. I'm sure you were

referring to a standard aircraft engine and not an electrically

dependent one. For Z-19 to be effective, the EFI/ECU/FP require at least

1 live feed. That source is not provided on the e-bus.


	


   Your electrically dependent engine accessories should

   run from always hot battery busses as illustrated in

   Z-19 and recommended for ALL the Z-figures. If you've

   got bad smells in the cockpit you should be able to

   open all the battery switches and kill the alternator

   and NOT have the engine stop.



   Bob . . .

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nuckolls.bob(at)cox.net
Guest

Posted: Tue Feb 19, 2008 8:47 am Post subject: Z-19 and multiple busses

At 09:01 AM 2/19/2008 -0700, you wrote:



 	  Quote: 	
		  Thanks for setting me straight. I was under the impression that normal 

operation would see both engine power switches on.


	


   The system would "function" with both switches ON. But

   the purpose for batteries is to have TWO, KNOWN sources

   of stored energy, one for the engine, one for other stuff.



   If you do your homework, you never have to close the second

   engine power switch except during a pre-flight test.



   Bob . . .

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