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nuckolls.bob(at)aeroelect
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 Posted: Wed Mar 22, 2017 4:39 pm Post subject: Lightweight rechargeable battery backup unit |
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At 07:16 PM 3/22/2017, you wrote:
| Quote: | --> AeroElectric-List message posted by: "BobD" <rjd(at)bobdawson.plus.com>
Bob, Thanks for responding to my post.
My aircraft is a part built Europa Tri-Gear, with a Rotax 912 ULS engine. |
Okay, how does fuel move from tanks to the
engine?
Bob . . .
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BobD
Joined: 05 Jan 2016
Posts: 112
Location: Sheffield UK
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| Posted: Thu Mar 23, 2017 12:01 am Post subject: Re: Lightweight rechargeable battery backup unit |
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Via the mechanical pump attached to the Rotax engine. Whilst it does have an electric pump, this is a backup to the mechanical one.
Whilst perhaps desirable, a backup method of power to the electric pump is not an LAA requirement, battery backup to the backup instruments is.
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_________________
Bob Dawson
Europa XS TG || 912 ULS || G-NHRJ || Dynon Skyview || PilotAware || SmartAss3 |
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nuckolls.bob(at)aeroelect
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| Posted: Fri Mar 24, 2017 7:55 am Post subject: Lightweight rechargeable battery backup unit |
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At 03:01 AM 3/23/2017, you wrote:
| Quote: | --> AeroElectric-List message posted by: "BobD" <rjd(at)bobdawson.plus.com>
Via the mechanical pump attached to the Rotax engine. Whilst it does have an electric pump, this is a backup to the mechanical one.
Whilst perhaps desirable, a backup method of power to the electric pump is not an LAA requirement, battery backup to the backup instruments is. |
Hmmmm . . . okay. Do the backup instruments have
dedicated input connections for backup power?
Do they feature or do you plan to have a
pilot operated power switch for these
devices?
Bob . . .
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BobD
Joined: 05 Jan 2016
Posts: 112
Location: Sheffield UK
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| Posted: Sun Mar 26, 2017 2:32 pm Post subject: Re: Lightweight rechargeable battery backup unit |
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Bob,
As far as I can see , the instrument itself has no facility for battery backup input, just the normal power feed
http://www.mglavionics.co.za/Infinitec/Manuals/ASX1.pdf
I therefore think the options are
1) go with a commercial device that has been suggested on the Europa Forum
http://www.mini-box.com/picoUPS-120-12V-DC-micro-UPS-battery-backup
with a small backup battery such as this
http://www.zbattery.com/Batteries/List-of-All-12Vs
2) build my own unit, as suggested in the post by user9253 (Joe Gores) in the original thread
3) Buy one of the more expensive units from either Funkework or LX Navigation with the battery backups built in
4) stick with the steam driven ASI and Altimeter.
I guess my priorities are accuracy, minimum weight, and cost in that order
I would value your opinion.
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Bob Dawson
Europa XS TG || 912 ULS || G-NHRJ || Dynon Skyview || PilotAware || SmartAss3 |
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user9253
Joined: 28 Mar 2008
Posts: 1944
Location: Riley TWP Michigan
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| Posted: Sun Mar 26, 2017 5:01 pm Post subject: Re: Lightweight rechargeable battery backup unit |
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That PicoUPS looks like it requires a backup battery. So I do not know what advantage it has over using a diode along with a backup battery.
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Joe Gores |
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nuckolls.bob(at)aeroelect
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| Posted: Mon Mar 27, 2017 5:11 am Post subject: Lightweight rechargeable battery backup unit |
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At 05:32 PM 3/26/2017, you wrote:
neat gizmo . . . does lots of interesting
things.
A standby battery is more a bureaucratic
philosophy than a strong mitigation of risk . . .
as an OBAM aircraft operator, it's pretty
much a given that you're going to fly with
an artfully maintained electrical system . . .
especially the battery. You will KNOW what
your battery-only endurance values are for
a pre-determined load which would, of course,
included the 50mA max demand of the ASX1.
It seems the practical need is to comply with
requirements and demonstrate a 'back up battery'
and offer an analysis of its performance and
a rational plan for insuring continued airworthiness.
I note that the ASX1 doesn't have a power switch
built in, so you not only need to provide a little
bundle of watt-seconds, you also need to manage
isolation that source when the ship is powered down.
Consider this:
[img]cid:.0[/img]
| Quote: | I guess my priorities are accuracy, minimum weight, and cost in that order
I would value your opinion. |
The legacy, alkaline 9v battery has a nominal
energy rating on the order of 500mAH. Suggest two
such batteries in series for a nominal operating
output of 16v falling to 12v at end of life.
The reason for suggesting these devices is their
WIRING. You can purchase snap-clips that make
good connection with the batteries. The 'ideal' cell
for a tiny DIY standby battery is the alkaline AA.
But battery trays for cylindrical cells are rather
flakey under environmental stress and you can't
routinely buy AA cells with welded tabs for low risk
soldering.
The schematic above shows two steering diodes that
insure power to the ASX1 from EITHER source
when the switch is closed. You need the switch to
(1) eliminate drain on the standby battery when
parked and (2) facilitate pre-and-post flight
testing of the installed batteries.
Your check-list would turn the ASX-1 on FIRST
to show that the device comes alive on the standby
battery. Then bring ship's power up and proceed
as you normally would.
The ASX-1 would be turned off last . . . again
showing that the battery is at least capable of
powering the instrument.
Requirements for continued air-worthiness would
simply call for replacing the batteries every year.
The alkaline cell will loose about 15% of capacity
in first year if stored at about 120F.
I stuck one of these batteries on the WestMountain Radio
Battery-runner-downer and it tells me that when the
fresh battery is loaded at 40mA (I de-rated from the
13.8V/50mA value in the manual . . . we're battery operating
at a slightly higher voltage into a constant power
demand).
[img]cid:7.1.0.9.0.20170326205809.05379958(at)aeroelectric.com.1[/img]
The fresh Duracell 9v delivered a solid 2 watt-hours at the
40mA rate. A pair of cells would be 4 watt-hours. At 14v
the specified demand of the ASX1 with the display illuminated
is 14v x 0.05A or 0.7W.
Hence, the pair of Duracell 9v batteries can be expected
to carry the instrument solidly for 6 hours . . . for
4+ hours at end of year assuming storage at elevated
temperatures.
The installed weight of this system would be under 0.3 pounds.
The bill of materials cost would be on the order of $10 which
includes the first year's compliment of batteries.
Continued air worthiness burden would be on the order of
$4/year assuming Sam's club prices for the 9v batteries.
Best yet, there is no burden of labor to verify the capacity
of a rechargeable back up system.
The FMEA looks good . . . the system gets pre and post-flight
tested.
This would seem to be the minimalist approach to meeting
the regulatory demand for a back up system that is, like a circuit
breaker, exceedingly unlikely to ever see real service.
Bob . . .
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kuffel(at)cyberport.net
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| Posted: Mon Mar 27, 2017 8:18 am Post subject: Lightweight rechargeable battery backup unit |
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Bob,
Hesitate to display my ignorance but with the schematic you drew won't the ASX-1 draw power from the higher voltage source, the batteries, until they are depleted to below the E-bus voltage? Won't replacing the diodes and SPST switch with a SPDT (even an on - off - on) with the center contact going to the ASX-1 solve the issue and provide the same functionality?
Tom Kuffel
 Virus-free. www.avast.com
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