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hammer408(at)comcast.net
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 Posted: Sun May 11, 2008 8:56 am Post subject: EFIS Battery Back-up Power |
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Bob:
I'm planning to install a AFS 3400 with it's own internal battery
back-up...... fused it to my Main Bus..
How I visualize: main alternator goes off line, I kill the alternator via
the master switch, turn on the E-Bus alternator feed switch....
Since the Main Bus will be de-energized due to a failed alternator, I assume
that the EFIS will utilize it's internal battery to keep the EFIS
energized..... OR
is my thought process all wrong !!!
Do I need a seperate switch on my panel to turn the EFIS off, eventhough the
Main Bus is de-energized....
What would the wiring architect be in this case ??
Thanks
Hank
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rshannon
Joined: 05 Sep 2007
Posts: 62
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| Posted: Sun May 11, 2008 9:46 am Post subject: EFIS Battery Back-up Power |
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Hank,
If you have just one EFIS, it (or if you have two, the first one) should be wired to the e-bus -- assuming you want to have the EFIS available during endurance (battery only) flight ops -- as most of us would like to have.
If you have two EFIS's, you may want to shut one down during endurance ops, and the second one would therefore be wired to the main bus. (If that second EFIS already has an automatic internal battery, you may have to shut it down manually even though it's on the main bus, to save that internal battery.) This is the way my dual AFS-3400 EFIS system is wired.
The e-bus is normally fed from the main bus through a one-way diode. When the alternator(s) fail, the e-bus alternate feed is turned ON which powers the e-bus direct from the battery, i.e., not through the main battery contactor. (For brief moment, the e-bus is then effectively fed from two places: the battery upstream of the battery contactor, and the main bus, from downstream of the battery contactor.) After the e-bus alternate feed has been turned ON, you immediately turn the main battery contactor OFF, to rapidly and positively shed those non-essential main bus loads. That's the sequence (e-bus alt feed ON, then main battery contactor OFF) to keep the e-bus powered and avoid rebooting things like your EFIS that are on the e-bus when you shut down the main.
When the e-bus alternate feed is ON, and the main battery contactor and main bus are OFF, the e-bus will not back feed the main bus because the diode keeps current from flowing from the e-bus to the main bus.
I hope that helps explain the desired function and results.
Ron
On Sun, May 11, 2008 at 12:58 PM, Henry Trzeciakowski <hammer408(at)comcast.net (hammer408(at)comcast.net)> wrote:
[quote] --> AeroElectric-List message posted by: "Henry Trzeciakowski" <hammer408(at)comcast.net (hammer408(at)comcast.net)>
Bob:
I'm planning to install a AFS 3400 with it's own internal battery
back-up...... fused it to my Main Bus..
How I visualize: main alternator goes off line, I kill the alternator via
the master switch, turn on the E-Bus alternator feed switch....
Since the Main Bus will be de-energized due to a failed alternator, I assume
that the EFIS will utilize it's internal battery to keep the EFIS
energized..... OR
is my thought process all wrong !!!
Do I need a seperate switch on my panel to turn the EFIS off, eventhough the
Main Bus is de-energized....
What would the wiring architect be in this case ??
Thanks
Hank
[b]
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livingjw(at)earthlink.net
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| Posted: Sun May 11, 2008 10:13 am Post subject: EFIS Battery Back-up Power |
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Why wouldn't you want to feed it directly from a battery bus with its own
switch? One wire, one switch, done. If you have two, EFISs then two wires,
two switches, done.
---
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JohnInReno
Joined: 08 Sep 2007
Posts: 150
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| Posted: Sun May 11, 2008 12:10 pm Post subject: EFIS Battery Back-up Power |
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Hi Henry,
Henry Trzeciakowski wrote:
| Quote: |
Bob:
I'm planning to install a AFS 3400 with it's own internal battery
back-up...... fused it to my Main Bus..
How I visualize: main alternator goes off line, I kill the alternator via
the master switch, turn on the E-Bus alternator feed switch....
I am at the same stage in my 9A project and I think it is important to
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be clear about the E-Bus terminology. You do not say what Z architecture
you are planning. I plan on a Z-13/8 strategy that has an SD-8 backup
alternator. I do NOT plan on an "endurance bus" like a traditional Z-11
architecture. In your scenario, killing the main alternator and
energizing the backup alternator will restore 8 amps of power to the
main bus. I expect the AFS 3500 and the Garmin GPS to stay up on their
internal batteries, if necessary, or the ships' battery while I switch
over. I will shed other loads with individual switches as necessary.
My only experience like this was a rented spam-can with my yoke mounted
Garmin. The first indication of an alternator failure came when the
Garmin complained, "external power lost". I have no idea how long the
alternator had been off line. Since then, I have discovered that the
Garmin 496 has all kinds of configurable alerts including a "low
voltage" that lets you set the threshold.
John
| Quote: | Since the Main Bus will be de-energized due to a failed alternator, I assume
that the EFIS will utilize it's internal battery to keep the EFIS
energized..... OR
is my thought process all wrong !!!
Do I need a seperate switch on my panel to turn the EFIS off, eventhough the
Main Bus is de-energized....
What would the wiring architect be in this case ??
Thanks
Hank
|
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_________________
John Morgensen
RV-9A - Born on July 3, 2013
RV4 - for sale |
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hammer408(at)comcast.net
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| Posted: Mon May 12, 2008 4:11 pm Post subject: EFIS Battery Back-up Power |
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Ron:
I'm using Z-11 architecture: single battery/single alternator. My e-bus is already carring about 12 amps, so the idea behind the internal battery EFIS was to wire to main bus. With that in mind, your explaination of the Alternator Failure Procedure is what I wasn't certain of and I believe you clarified and confirmed it.
Alternator Failure: 1- E-bus alternate feed is turned ON which powers the
e-bus directly from the battery.
2- Immediately turn the Main Battery
Contactor OFF (DC Master Power Switch) - Main Bus is now off-
line, main bus drops below about 12 volts and the EFIS resorts to it's
internal battery.
and no additional switches would be necessary.
Thanks
Hank
[quote] ---
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