Today's Message Index:
----------------------
1. 07:59 AM - Dual Alternator, Dual Battery, Single Bus (Dan Brown)
2. 09:45 AM - Re: Re: Power Generation without Battery? (Robert L. Nuckolls, III)
3. 12:42 PM - Re: Dual Alternator, Dual Battery, Single Bus (Robert L. Nuckolls, III)
4. 01:31 PM - Re: Power Generation without Battery? (user9253)
5. 03:13 PM - Re: Re: Power Generation without Battery? (Robert L. Nuckolls, III)
6. 03:23 PM - ASTM membership is now active . . . (Robert L. Nuckolls, III)
7. 04:18 PM - Re: Power Generation without Battery? (user9253)
8. 04:43 PM - Re: Power Generation without Battery? (user9253)
9. 05:18 PM - FMEA (user9253)
10. 06:18 PM - Re: Re: Power Generation without Battery? (Robert L. Nuckolls, III)
11. 06:44 PM - Re: Power Generation without Battery? (user9253)
12. 07:07 PM - Re: Re: Power Generation without Battery? (Robert Borger)
Message 1
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| Subject: | Dual Alternator, Dual Battery, Single Bus |
Hello Bob,
My project will have a dual electronic ignition and an all-electric panel. I
intend to have the two battery and individual battery buses per your Figure
Z-30. I will have a single power bus that is supplied by a 60 amp main
alternator (Plane Power AL12-C60) with a 30 amp backup alternator (Plane
Power FS1-14). The B-leads from both alternators are connected through a
Maxi fuse block to the hot side of the starter contactor which then goes
through the firewall to the bus.
I have some questions:
1) The 6 AGW B-leads from the alternators can easily carry 80 amps. Can
I protect the both leads with 80 amp Maxi fuses? I believe I might have read
that this is okay in the List FAQs.
2) According to Hartzell Engine Technologies (new owners of Plane Power
alternators) the main alternator puts out 14.2 v and the backup puts out
13.6 v so if the main drops below 13.6 v the backup takes over. Their
wiring diagram does not show a diode in the circuit to stop the flow of
electricity from the bus to the B-terminal of the backup alternator. I
thought that this may affect the backup alternators life but the technician
at HET said not to worry about it. If I was really concerned I could turn
the field off on the backup under normal operation and turn it on in the
event of a low voltage indication. I prefer the automatic takeover of the
backup so my question is this, do I need to have a diode in the circuit to
block the reverse flow to the backup alternator or is the 0.6 v potential no
big deal? If it is prudent to add the diode what type of diode do you
recommend?
3) I also think I remember reading in the List FAQs (but can't seem to
find it) that in the event of the battery contactor opening and
disconnecting the battery from the bus, a load on the bus could cause
precipitous failure of the alternator. It would be nice to have a battery
contactor open indicator light. What is the best way to add such a device to
your dual battery circuit?
Thanks,
Dan
Message 2
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| Subject: | Re: Power Generation without Battery? |
At 09:11 2015-01-24, you wrote:
>
>Lightspeed and others recommend connecting electronic ignition
>directly to the battery.
. . . a sentiment that has been echoed in the AEC publications
for a long time. Fuel pumps too . . . any component which depends
on DC to keep the engine running . . .
> Since Lithium batteries have been known to short out, maybe they
> should not be used.
SLVA batteries never short?
> If the battery shorts out, so will the alternators be shorted.
. . . okay, step through the FMEA for a shorted cell in
any battery. How will the event manifest? How will the
pilot become aware of it? What is the recommended plan
of action to be taken by the pilot? Most important . . .
what features can be incorporated into the full-up system
to offer a pilot the best response to the event?
> Another failure mode to be considered is a failed master
> contactor shortly after takeoff.
Again, step through the FEMA . . .
> That is not very likely to happen, but it could. Regardless of
> what the manufacturers say, an alternator could keep supplying
> power to the aircraft electrical system.
Yes . . . consider the plots of data I took on an exemplar
SD-8 at B&C about 20 years ago
http://tinyurl.com/n5yd3vw
In particular, page 9 of the document that cites 14.5v output
at 9.7 amps with a 10KuF 'smoothing' capacitor and NO BATTERY.
One a quality we've not discussed here is the value of the
legacy 'smoothing' capacitor might add in improving NO BATTERY
performance of the rectifier-regulator. A question I will explore
in the future.
> Thus the pilot would not know that the master contactor has
> opened. If the duration of the flight is longer than the energy
> stored in the battery (likely with a Li battery), then the engine
> will quit. A solution to the failed master contactor scenario is a
> relay in parallel (disabled during engine cranking).
That's one solution . . . are there others?
> Even if these failure modes are unlikely, everything needs to be
> considered when designing an electrical system. Accidents happen
> sometimes due to unlikely and unexpected chain of events.
. . . but with some tempering based on lessons learned
and probabilities based on history. Yeah, on occasion
some airplanes throw a prop . . . bad bolts? Probably
not. Bad installation of bolts? Probably. Broken
crankshaft . . . that's a stretch. But again, history
has demonstrated the MAJOR cause of uncomfortable
termination of flight is inattention to simple-ideas
with performance histories rich in data.
Bob . . .
Message 3
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| Subject: | Re: Dual Alternator, Dual Battery, Single Bus |
At 09:58 2015-01-25, you wrote:
>Hello Bob,
>My project will have a dual electronic ignition and an all-electric
>panel. I intend to have the two battery and individual battery buses
>per your Figure Z-30. I will have a single power bus that is
>supplied by a 60 amp main alternator (Plane Power AL12-C60) with a
>30 amp backup alternator (Plane Power FS1-14). The B-leads from both
>alternators are connected through a Maxi fuse block to the hot side
>of the starter contactor which then goes through the firewall to the bus.
>I have some questions:
>1) The 6 AGW B-leads from the alternators can easily carry 80
>amps. Can I protect the both leads with 80 amp Maxi fuses? I believe
>I might have read that this is okay in the List FAQs.
Yes . . . as long as your bus feeder protection is much more
robust than the downstream protection . . . you can choose
about anything.
Consider the chain of protection for some device you might
plug in the wall . . .
Protection within the device needs to be much faster than
the breaker that feeds that outlet considering that it
too may be loaded to the maximum continuous rating of
the device. In other words, the failure inside the appliance
needs to have a small fraction of total effects on the
breaker in the panel. As you move upstream in the distribution
system, each branch is protected with careful attention
to dynamics such that a small event in somebody's house
doesn't trigger a 'blackout' in the neighborhood.
It might be better to use the miniature current limiters
like . . .
http://tinyurl.com/qj4vojb
In holders with vertical studs upon which you stack
the current limiter tabs and any/all ring terminals
with good force.
>2) According to Hartzell Engine Technologies (new owners of
>Plane Power alternators) the main alternator puts out 14.2 v and the
>backup puts out 13.6 v so if the main drops below 13.6 v the backup takes over.
Yes . . . B&C pioneered that philosophy 20+ years
ago when we introduced the first pad-driven, wound-
field alternators into OBAM aviation.
> Their wiring diagram does not show a diode in the circuit to
> stop the flow of electricity from the bus to the B-terminal of the
> backup alternator. I
Doesn't need it. Alternators, unlike generators, are
incapable of taking power INTO their b-terminal. They
have diodes built in. See:
http://tinyurl.com/okegwfd
> thought that this may affect the backup alternators life but the
> technician at HET said not to worry about it.
. . . now, if he had only explained why you wouldn't
have been left with a dangling question . . .
>If I was really concerned I could turn the field off on the backup
>under normal operation and turn it on in the event of a low voltage
>indication. I prefer the automatic takeover of the backup so my
>question is this, do I need to have a diode in the circuit to block
>the reverse flow to the backup alternator or is the 0.6 v potential
>no big deal? If it is prudent to add the diode what type of diode do
>you recommend?
Absolutely not. Wire with guidance from Figure Z-12 which
describes the ancestral configuration . . .
http://tinyurl.com/ag46m2f
>3) I also think I remember reading in the List FAQs (but can't
>seem to find it) that in the event of the battery contactor opening
>and disconnecting the battery from the bus, a load on the bus could
>cause precipitous failure of the alternator. It would be nice to
>have a battery contactor open indicator light. What is the best way
>to add such a device to your dual battery circuit?
As long as you don't have 250w incanescant landing lights
or an electro-hydraulic pump system, transient loads
capable of stalling a self-excited alternator don't
exist. Further, since you're running dual batteries,
you'd have to crap two contactors to set that scenario
up.
What does your power distribution look like. What electro-whizzies
from which which busses?
Bob . . .
Message 4
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| Subject: | Re: Power Generation without Battery? |
> I'd like to monitor battery temp using a probe and my on board electronics, and
to have some way to electrically isolate or even physically remove the battery
Here a links to thermocouples. Most EMS or EFIS have inputs for type J.
http://www.omega.com/pptst/WT.html
http://www.omega.com/pptst/SA2.html
If the EFIS alarms with temperature rise, the master switch can be shut off.
> So I am concerned about the Li battery being a single point of failure capable
of stopping the engine.
> How can I design around this problem?
Are there any permanent magnet alternators (dynamo) available for your engine?
One possibility (and I am not necessarily recommending this) is to dedicate a
dynamo to supply electrical power to only one fuel pump and one ignition, keeping
this circuit completely isolated and independent of the rest of the aircraft
electrical system (except for common ground).
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=437626#437626
Message 5
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| Subject: | Re: Power Generation without Battery? |
At 15:30 2015-01-25, you wrote:
> I'd like to monitor battery temp using a probe and my on board
electronics, and to have some way to electrically isolate or even
physically remove the battery
Here a links to thermocouples. Most EMS or EFIS have inputs for type J.
http://www.omega.com/pptst/WT.html
http://www.omega.com/pptst/SA2.html
If the EFIS alarms with temperature rise, the master switch can be shut off.
But where do you put a thermocouple? In a
4x4 array of cells, there are 16 potential
failures. How can you be certain that monitoring
any particular location outside the battery will
offer timely notification of a failure on any
of the 16 cells inside?
What constitutes an alarming temperature rise?
Once that condition is noted, what value is there
in any pilot action. Shut off the battery? Jettison
the battery?
> So I am concerned about the Li battery being a single point of
failure capable of stopping the engine.
> How can I design around this problem?
Design a system that doesn't set batteries on fire (timely
notification of or reaction to over voltage) and perhaps
incorporate batteries with full-up Battery Management Systems
that will function to PREVENT such events as opposed to reacting
to the event AFTER it occurs.
Are there any permanent magnet alternators (dynamo) available for
your engine? One possibility (and I am not necessarily recommending
this) is to dedicate a dynamo to supply electrical power to only one
fuel pump and one ignition, keeping this circuit completely isolated
and independent of the rest of the aircraft electrical system (except
for common ground).
Please make the argument for the battery (of any chemistry)
NOT being the most reliable source of energy on the
airplane. We've read narratives for all manner
of puffed-up and/or vented-dry SVLA batteries . . .
some of which have indeed experienced internal fires.
ALL such cases were preceded by a sustained ov even
that went unnoticed. Batteries don't instantly go
POOF when the alternator runs away. To this date, are
we aware of ANY battery in distress that was NOT
triggered by an event borne of poor system architecture
or operator inattention?
Bob . . .
Message 6
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| Subject: | ASTM membership is now active . . . |
Just finished the keystrokes needed to join ASTM.
I downloaded a constellation of specs relevant to
the LSA market. Got some reading to do . . .
Bob . . .
Message 7
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| Subject: | Re: Power Generation without Battery? |
Chris,
My mistake, I should have read your first post more closely. You do intend to
use the SD-8 dynamo.
The Rotax 912i fuel injected engine has two dynamos, one for the engine and one
for the rest of the aircraft. The ignition and fuel pumps can also be powered
by the other dynamo if necessary.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=437632#437632
Message 8
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| Subject: | Re: Power Generation without Battery? |
> Please make the argument for the battery (of any chemistry) NOT being the most
reliable source of energy on the airplane.
I agree that SVLA are very reliable. I am not very knowledgeable about the Lithium
batteries except for the news reports which sensationalize the fire without
explaining why it happened. If you think that the Lithium batteries are safe
(if properly charged and discharged) for use in aircraft, then that is good
enough for me. But I will wait until the price comes down to the level of lead
acid batteries before buying a Lithium. In the mean time, I will keep my plane
light weight by watching what I eat. :-)
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=437633#437633
Message 9
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> . . . okay, step through the FMEA for a shorted cell in
> any battery. How will the event manifest? How will the
> pilot become aware of it? What is the recommended plan
> of action to be taken by the pilot? Most important . . .
> what features can be incorporated into the full-up system
> to offer a pilot the best response to the event?
Good suggestion and worthy of a new thread. A shorted AGM battery is highly unlikely.
But I think the symptoms would be low system voltage and high current
on the ammeter no matter if the shunt measures battery current or alternator
output. Of course the pilot would not know what the problem is. There could
be a short external to the battery (which is more likely). The prudent thing
to do would be to shut off the master switch and land to investigate the problem.
Another interesting failure is of the master contactor coil. How will the pilot
know? If the alternator keeps working, which is likely, then there might
not be any clues. The voltage will remain the same. An alternator load meter
will not change much. An ammeter that measures battery charge-discharge current
will be on zero, not far from where it usually is. The pilot might not realize
the contactor coil failed until he closes the throttle or maybe not until
the next engine start.
It would be worthwhile to analyze each component of the electrical system and
ask, if this part fails, how will I know and what should I do about it.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=437636#437636
Message 10
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| Subject: | Re: Power Generation without Battery? |
At 18:16 2015-01-25, you wrote:
>
>Chris,
>My mistake, I should have read your first post more closely. You do
>intend to use the SD-8 dynamo.
> The Rotax 912i fuel injected engine has two dynamos, one for the
> engine and one for the rest of the aircraft. The ignition and fuel
> pumps can also be powered by the other dynamo if necessary.
The last time I dug through the MM on a 912, a
constellation of windings on the PM alternator
stator core were defined as follows:
Emacs!
4 each, trigger coils for spark timing of the
8 plugs in pairs (waste spark). These
will be a low voltage, low energy
signal to the ignition modules.
2 each, capacitor charging coils, one for
each module. These are moderate energy,
high voltage windings that charge a
capacitor with each pass of the magnet.
This few hundred volts of capacitor
charge is stepped up in coils to the
killovolt levels needed for plugs.
1 each, tachometer signal coil. Another
low voltage, low energy signal generator
for an electronic tach.
1 each, PM alternator coil. High energy, high
current in the 250W class. This is the
only winding available to drive any
sort of rectifier-regulator to operate
ship's electro-whizzies.
All other windings are separate and dedicated
to their respective tasks thus making ignition
systems completely independent of the power
generation system.
Some Rotax installations include aa SECOND,
optional belt driven alternator in the 40-55A class.
This second alternator has been teamed with
the integral PM alternator in a Figure Z-13/8
configuration on several OBAM aircraft . . .
I've seen some pad driven alternators on
Rotax engines . . . in the spot for
vacuum pumps. But this pad is slow and
I don't think THAT particular #2 alternator
was very practical.
In any case, only one coil of eight on the
back of a Rotax 912/914 generates power
for ship's electrical needs.
Bob . . .
Message 11
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| Subject: | Re: Power Generation without Battery? |
The Rotax fuel injected engine is new, only having been for sale for the last year
or two. It is an electrically dependent engine, not only for the ignition,
but also for the high pressure fuel pumps. Thus, the electrical system needs
to be fail safe. Below is an excerpt from the installation manual.
http://www.flyrotax.com/customer-serviceImpressum/technical-publications.aspx
Joe
> The internal generator has two isolated coils integrated (individual generators).
During the starting operation, the EMS system is powered by the battery.
With sufficient speed generator B takes over this function. After the EMS system
check, generator A takes over the supply of the EMS system (engine), if the
switching threshold is exceeded. Generator B is then used to supply the aircraft
instruments and for charging the battery.
> Generator A 14.2 V/16 A (220 W nominal capacity at 20C/68 F)
> Generator B 14.2 V/30 A (420 W nominal capacity at 20C/68 F)
>
> If generator A fails, generator B takes over its functions. The onboard computer
and the instruments will be supplied by the battery. The battery will no
longer be charged!
>
> If generator B fails, the battery will no longer be charged. The engine still
runs on generator A and the instruments will be supplied by the battery. The
function of the instruments depends on the state of charge of the battery.
> For monitoring the battery voltage and to ensure that the battery is charged,
a voltmeter and ammeter is necessary.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=437640#437640
Message 12
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| Subject: | Re: Power Generation without Battery? |
Bob,
FWIW, I have one of those (Nippon Denso) alternators on the vacuum pad of my 914.
It is actually capable of producing more amps than the ROTAX built-in alternator.
But it takes 2500 rpm for it to come online.
Best regards,
Robert Borger, President
Geowhiziks & Doodlebugging, Inc.
Certified Petroleum Geophysicist AAPG#101
3705 Lynchburg Dr.
Corinth, TX 76208-5331
(C) 817-992-1117
Sent from my iPad
> On Jan 25, 2015, at 19:17, Robert L. Nuckolls, III <nuckolls.bob@aeroelectric.com>
> I've seen some pad driven alternators on
> Rotax engines . . . in the spot for
> vacuum pumps. But this pad is slow and
> I don't think THAT particular #2 alternator
> was very practical.
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