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Schottky diode

 
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trigo(at)mail.telepac.pt
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PostPosted: Fri Nov 17, 2017 9:29 am    Post subject: Schottky diode Reply with quote

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: 1907
Location: Riley TWP Michigan

PostPosted: Fri Nov 17, 2017 10:08 am    Post subject: Re: Schottky diode Reply with quote

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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nuckolls.bob(at)aeroelect
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PostPosted: Fri Nov 17, 2017 3:04 pm    Post subject: Schottky diode Reply with quote

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
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PostPosted: Sun Nov 19, 2017 11:56 am    Post subject: Schottky diode Reply with quote

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
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PostPosted: Sun Nov 19, 2017 5:08 pm    Post subject: Schottky diode Reply with quote

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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