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Schottky diode

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trigo(at)mail.telepac.pt
Guest

Posted: Fri Nov 17, 2017 9:29 am Post subject: Schottky diode

Guys



In my RV-10 electric system, with 2 batteries and 2 alternators (the Primary ALT being a Plane Power 60A, and the Secondary ALT being a BC410-H, formerly known as SD-20), I have a Main Battery contactor and an Aux Battery contactor.



This being, unless I have the Aux Batt contactor On (closed), the Alternators will not charge the Aux battery.



Therefore, I am thinking in installing a Schottky diode (I have one from Perihelion Design sitting in my shelf, which is rated at 60A of maximum allowable continuous current, and voltage loss around 0,20V), between the Main battery Buss and the Aux battery + terminal, to allow the alternators who are charging the Main battery, also to charge the Aux battery, even when the Aux BATT contactor is not closed.



First question: is there any downside to this solution, or is it even not recommended at all?



Second question (or more...): in this solution, I should put a fuse in the wire between the Main Batt buss and the Schottky diode, to protect this wire, right? 

Which is the A recommended for this fuse, 30 A?

And by the way, which wire gauge, AWG#12?



Thanks 

Carlos

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user9253

Joined: 28 Mar 2008
Posts: 1944
Location: Riley TWP Michigan

Posted: Fri Nov 17, 2017 10:08 am Post subject: Re: Schottky diode

Your plans sound good to me.  Wires should be fused at the source end.  Since the wire with the diode connects two sources (batteries) together, you might consider fusing it at both ends, especially if it is a long wire or if there is any chance of it shorting to ground.

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_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Nov 17, 2017 3:04 pm Post subject: Schottky diode

At 10:53 AM 11/17/2017, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: Carlos Trigo <trigo(at)mail.telepac.pt>



 Guys



 In my RV-10 electric system, with 2 batteries and 2 alternators (the Primary ALT being a Plane Power 60A, and the Secondary ALT being a BC410-H, formerly known as SD-20), I have a Main Battery contactor and an Aux Battery contactor.



 This being, unless I have the Aux Batt contactor On (closed), the Alternators will not charge the Aux battery.



 Therefore, I am thinking in installing a Schottky diode (I have one from Perihelion Design sitting in my shelf, which is rated at 60A of maximum allowable continuous current, and voltage loss around 0,20V), between the Main battery Buss and the Aux battery + terminal, to allow the alternators who are charging the Main battery, also to charge the Aux battery, even when the Aux BATT contactor is not closed.



 First question: is there any downside to this solution, or is it even not recommended at all?



 Second question (or more...): in this solution, I should put a fuse in the wire between the Main Batt buss and the Schottky diode, to protect this wire, right? 

 Which is the A recommended for this fuse, 30 A?

 And by the way, which wire gauge, AWG#12? 	


   Why not wire like Z-12 with a z-30 second

   battery?  Are you planning to have battery

   bus(es)? Which electro-whizzies will run

   from each bus? Why not fly with both

   battery contactors closed?



 

 

   Bob . . .

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trigo(at)mail.telepac.pt
Guest

Posted: Sun Nov 19, 2017 11:56 am Post subject: Schottky diode

Hi Bob

 

Please see my answers below

 

De: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] Em nome de Robert L. Nuckolls, III

Enviada: Friday, November 17, 2017 11:04 PM

Para: aeroelectric-list(at)matronics.com

Assunto: Re: Schottky diode

 

At 10:53 AM 11/17/2017, you wrote:



 	  Quote: 	
		  

--> AeroElectric-List message posted by: Carlos Trigo <trigo(at)mail.telepac.pt (trigo(at)mail.telepac.pt)>



Guys



In my RV-10 electric system, with 2 batteries and 2 alternators (the Primary ALT being a Plane Power 60A, and the Secondary ALT being a BC410-H, formerly known as SD-20), I have a Main Battery contactor and an Aux Battery contactor.



This being, unless I have the Aux Batt contactor On (closed), the Alternators will not charge the Aux battery.



Therefore, I am thinking in installing a Schottky diode (I have one from Perihelion Design sitting in my shelf, which is rated at 60A of maximum allowable continuous current, and voltage loss around 0,20V), between the Main battery Buss and the Aux battery + terminal, to allow the alternators who are charging the Main battery, also to charge the Aux battery, even when the Aux BATT contactor is not closed.



First question: is there any downside to this solution, or is it even not recommended at all?



Second question (or more...): in this solution, I should put a fuse in the wire between the Main Batt buss and the Schottky diode, to protect this wire, right? 

Which is the A recommended for this fuse, 30 A?

And by the way, which wire gauge, AWG#12?

 

Regards

Carlos  	




  Why not wire like Z-12 with a z-30 second battery? 

 

You’re spot on, I do have both arquitectures in my system:

  - like in Z-12, the B-Leads of my 2 alternators are both connected to the same lug in the Starter contactor, thus both alternators charge the Main Battery

  - like in Z-30, the Aux battery is connected, through the Aux Batt. Contactor, to the downstream lug of the Main Batt contactor, thus the Aux battery will act as a direct “reinforcement” for the Main battery

 

 Are you planning to have battery bus(es)? Which electro-whizzies will run from each bus?

 

I have what you call a “Battery bus” and I called an “Always Hot buss”, directly connected to the Main Battery, only to power the Fuel boost pump and a cockpit light

And I have what I called an “Avionics Backup buss”, which gets power directly from the Aux battery, through a dedicated relay/contactor, to the secondary power inputs of all my GARMIN Avionics

 

Why not fly with both battery contactors closed?

In this case, this is indeed the one-million-dollar question.

My initial request was about to put an extra wire and a Schottky diode, between the Main battery buss and the Aux battery + terminal, to be able to charge the Aux battery without closing the Aux Batt contactor.

And this idea had 2 backgrounds: in case the pilot forgets to turn On the Aux Batt contactor, or in case he doesn’t want to turn it On, to “save” the Aux Battery power (this last being probably a dumb idea).

 

What do you think about your own question?

 

Carlos

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nuckolls.bob(at)aeroelect
Guest

Posted: Sun Nov 19, 2017 5:08 pm Post subject: Schottky diode

 	  Quote: 	
		  

   Why not wire like Z-12 with a z-30 second battery? 

  

 You’re spot on, I do have both arquitectures in my system:

   - like in Z-12, the B-Leads of my 2 alternators are both connected to the same lug in the Starter contactor, thus both alternators charge the Main Battery 	


   Are you intending to use the LR3 generic controller

   or the SB1B-14 controller specific to stand-by service?



  	  Quote: 	
		    - like in Z-30, the Aux battery is connected, through the Aux Batt. Contactor, to the downstream lug of the Main Batt contactor, thus the Aux battery will act as a direct “reinforcement” for the Main battery 	


   Okay . . .



  	  Quote: 	
		   

 Are you planning to have battery bus(es)? Which electro-whizzies will run from each bus?

  

 I have what you call a “Battery bus” and I called an “Always Hot buss”, directly connected to the Main Battery, only to power the Fuel boost pump and a cockpit light 

 And I have what I called an “Avionics Backup buss”, which gets power directly from the Aux battery, through a dedicated relay/contactor, to the secondary power  inputs of all my GARMIN Avionics 	


   Understand . . .



  	  Quote: 	
		   

 Why not fly with both battery contactors closed?



 In this case, this is indeed the one-million-dollar question.

 My initial request was about to put an extra wire and a Schottky diode, between the Main battery buss and the Aux battery + terminal, to be able to charge the Aux battery without closing the Aux Batt contactor.

 And this idea had 2 backgrounds: in case the pilot forgets to turn On the Aux Batt contactor, 	


    I really get exercised over the phrase, "Pilot forgets" . . .

    Pilots in control of their airplanes don't forget actions

    necessary for competent use of the machine . . . pilots

    along for the ride are at risk for unhappy days far

    worse than improperly positioned controls . . . check

    lists used a few dozen times become as automatic as breathing.



  	  Quote: 	
		   . . . or in case he doesn’t want to turn it On, to “save” the Aux Battery power (this last being probably a dumb idea).

 What do you think about your own question? 	




    A significant advantage of two batteries is

    the ability to isolate the 'avionics' battery

    during cranking to side step brown-out issues.

    The disadvantage is added weight . . . and 2x

    the cost of ownership for battery maintenance

    efforts . . . added complexity.



    With two alternators, battery only endurance

    is insignificant. Hence no reason to fret over

    battery capability beyond that need to get

    the engine running.



    It occurs to me that I've never measured the

    brownout characteristics of the lithium ion

    products. Given their significantly lower

    source impedance, it just might be that these

    engine cranking sources would support the

    bus at or above the brown-out limits of the

    glass-panel products with weak-knees. Has

    anyone on the List explored this?



    My Sedona has a PM starter on it. I'll put a

    task on the to-do bucket to capture a cranking

    event trace on the EXP36 battery I have on hand.



    Except for mitigation of a brown-out event

    (which generally lasts a less than 100

    milliseconds), I'm having trouble warming up

    to a two-battery configuration. With two

    alternators a well maintained battery, I can't

    think of any other failure scenario where two

    batteries are going to yield a return on investment.



    Can't think of a reason your 'avionics bus'

    should be any different than the legacy e-bus.



 

   Bob . . .

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