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art(at)zemon.name
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 Posted: Sun Aug 06, 2017 9:42 am Post subject: Backup Alternator / Backup Battery Sanity Check |
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Folks,
Can you give me a sanity check? I am building a Bede BD-4C with an MGL EFIS. This is largely a mechanical airplane so manual trim, no gear motors, manual flaps, etc. Between the low current consumption of the EFIS and using LED lights, a backup alternator will run everything in the airplane except the pitot heater; the typical current draw is 21.57 amps and maximum is 31.49 amps. (Pitot heat adds 10 amps.)
With that in mind, I plan on including a 30 amp backup alternator and no backup battery. I figure:
- If the engine is turning, I will certainly have one of the two alternators operable.
- If the engine is not turning, the main battery ought to keep the electrons flowing until I reach the ground.
Am I missing anything?
-- Art Z.
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https://CheerfulCurmudgeon.com/"If I am not for myself, who is for me? And if I am only for myself, what am I? And if not now, when?" Hillel
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user9253
Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan
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| Posted: Sun Aug 06, 2017 12:13 pm Post subject: Re: Backup Alternator / Backup Battery Sanity Check |
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With the pitot heater shut off, I would expect the continuous current draw to be closer to 10 amps. Have you actually measured 21 amps? Regardless, the backup alternator should run everything.
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Joe Gores |
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art(at)zemon.name
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| Posted: Sun Aug 06, 2017 5:47 pm Post subject: Backup Alternator / Backup Battery Sanity Check |
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Joe,
See the Amps table on my electrical system overview diagram. It comes to 21.57 amps typical, 31.49 amps maximum.
Cheers,
-- Art Z.
On Sun, Aug 6, 2017 at 3:13 PM, user9253 <fransew(at)gmail.com (fransew(at)gmail.com)> wrote:
| Quote: | --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>
With the pitot heater shut off, I would expect the continuous current draw to be closer to 10 amps. Have you actually measured 21 amps? Regardless, the backup alternator should run everything.
--------
Joe Gores |
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https://CheerfulCurmudgeon.com/"If I am not for myself, who is for me? And if I am only for myself, what am I? And if not now, when?" Hillel
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user9253
Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan
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| Posted: Sun Aug 06, 2017 6:42 pm Post subject: Re: Backup Alternator / Backup Battery Sanity Check |
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Art, I see what you mean. It will be interesting to see how measured current compares to calculated current. You have nice neat documentation.
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