Today's Message Index:
----------------------
1. 09:06 AM - Re: Re: Power Generation without Battery? (Robert L. Nuckolls, III)
2. 01:20 PM - Internal Shunt in Alternator? (Justin Jones)
3. 04:43 PM - Re: Internal Shunt in Alternator? (Robert L. Nuckolls, III)
4. 05:53 PM - Electrical System with Dual Batteries & Brownout Prevent (Jeff Page)
Message 1
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Subject: | Re: Power Generation without Battery? |
At 12:05 2015-01-30, you wrote:
Bob,
Thanks to you and other participants for help with my questions.
Interesting that you are feeling so confident in the application of
Li batteries. This is really a significant step forward in technology
for small aircraft.
I have not said that it's a "step forward" . . . in fact,
I have raised questions as to the economics for the transition
to lithium. I will assert that lithium is an alternative
ingredient that may well be an appealing recipe for success.
I don't yet see a concise definition of 'success'.
There are three separate lines of inquiry that influence the
choice to incorporate lithium batteries into your personal
elegant solution.
Integration: It's no different than the study of how
transistors evolved with significant milestones marked
by the relative fragility of the PNP germanium
transistors that first flew in airplanes. Devices later
displaced with more robust NPN silicon. More recently,
the power mosfet is King Silicon. EVERY evolutionary
plateau was an improvement in performance, robustness
and service life. However, EVERY step up required major
changes to the circuitry and design philosophy to fully
exploit what the new device had to offer. One could not
simply pull out the old and plug in the new. This is
the foundation for my distaste of popular marketing
hype citing "lead-acid equivalency".
Lithium is equivalent to nothing . . . its greatest
advantages cannot be fully exploited without careful
attention to just how this ingredient 'fits' into
the recipe for success.
Cost of Ownership: When Burt Rutan was putting the sharp
pencil to the design of Voyager, weight was a critical
consideration.
He told us that it takes 5 pounds of fuel to carry
one pound of airplane around the world. Every pound
removed from empty weight removes 6 pounds from gross
weight at takeoff. Nearly one gallon more fuel. One gallon
at end of mission would carry Voyager another hundred
miles or so. But there were prices to pay. The materials
to build such a 'featherweight' airplane with any structural
integrity were very expensive. Further, fuel unique mission
requirement multiplies the weight of the airplane by 6 times
called for a fuel tank with wings having very attractive
l/d ratios . . . at the sacrifice of handling qualities.
Dick Rutan confessed that the airplane scared the hell
out of him . . . he had nightmares of dying in that
airplane. Without the fine support of King Radio for
an autopilot that would handle this winged beast,
the around-the-world mission would have humanly
impossible. Without pedantic attention to weight,
sometimes a great cost, the mission might not have been
possible.
Risk: Properly conducted FMEA seek to study, discover,
classify, understand and ultimately mitigate all the
ways that the product can first, cease to preform
intended duties as one of many players in the orchestra.
Then, mitigate failures that put the entire system at risk for
catastrophic collapse. It's one thing for the cello
player to break a string . . . quite another for
to be sneezing H1N1 into the surrounding environment.
You emphasized to "operate (Lithium battery) within well established
limits and preventative maintenance to verify integrity." Will you
elaborate regarding how this looks with Li? You have mentioned in
the past about the lack of data from many manufacturers, and the lack
of lead acid equivalency. Do you feel the BMS used by EarthX is a
final equilibrator here?
The purveyors of lithium are the first folks to assert
that battery management systems are always a 'good'
idea. What ever form they take, the BMS mitigates risk
for catastrophic failure. Just how the BMS is configured
and applied in practice a big factor in performance, risk
and cost of ownership. It's unreasonable and added risk
to expect the consumer (OBAM aircraft builder) to take
on yet another task that amounts to micro-managing the
lithium physics. Especially when compared to the mature,
relatively docile qualities of lead-acid. BMS may not
be the 'final' answer to the svla vs. lithium decision
but certainly a major consideration.
An this still leaves the question I've asked and
nobody has come forward to answer, "What are the
numbers . . . how will the smaller weight and volume
numbers manifest in the performance and utility of
say, an RV7 presently fitted wity a PC680? Shorter
takeoffs? Higher mountains to challenge, cleared
out space to store your sandwiches?
Boeing's considerations for battery weight were but one
component in a HUGE model of cost/benefit ratios. The numbers
they considered enticed them to spend $millions$ in making
the switch to lithium. What are YOUR numbers?
The advanced EFII system I have been evaluating may be a bit too far
up the ladder for my project, as you pointed out. The 10 ampere
requirement quoted was per email from manufacturer and is for both
the fuel and ignition systems. Majority apparently consumed by the
fuel pump - one of two runs at a time to pressurize a fuel rail.
Yes . . . and I've heard 'up and running' numbers on
that system 'quoted' from 6 to 10 amps . . . but I have
yet to discover published data that speaks to the real
energy requirements for this system.
People may snicker at my insistence that the purveyors of
lithium come forth with "all the numbers" . . . like
Hawker/Enersys and virtually all contemporaries. But as
Lord Kelvin often opined, "without the numbers you have
barely scratched the surface of the science." I will build
on that sentiment by suggesting that the decision should not
devolve to preferring Big Macs just because they taste good
without knowing how they integrate into the energy
conversion/management system of a very complex machine.
Questions that remain undiscovered, unasked, unanswered
and/or ill-considered may bring the system down no matter
how good the product tasted.
EFII "owes" you the same quality of numbers that we expect
from Rotax, AeroVoltz, Icom, Smiley Jack's Prop Shop
. . . or anybody else that wants to play honorably and capably
in this sandbox.
Anyway, I am currently favoring a pullback to a set of P Mags,
mechanical fuel injection, a single Li battery with a small detached
back up, and a single alternator. This set up should perform
similarly in practical terms, and be very reliable and light.
Sounds like a considered move . . . what now are your
electrical system numbers insuring comfortable termination
of flight limited only by fuel aboard?
Are you going to have a vacuum pump? Why waste a
perfectly good energy source by covering the pump
pad with a plate of aluminum? After nearly 20 years
of sifting the numbers, FMEA scenarios, costs of
ownership and performance, I suggest that Figure Z-13/8
is as near 'perfection' for flight system reliability
. . . assuming of course that you don't burden it with
an 120 watt engine support demands.
You speak of two batteries . . . why? One or both lithium?
Can you share your FMEA and cost of ownership reasoning?
Exactly how will that savings of wight manifest in performance
or utility of your airplane . . . and at what cost of
hours to integrate and maintain performance at minimum
levels throughout the service life of the battery?
Z-13/8 will keep your panel lit and allow you to
run any battery until it won't crank the engine any
more. The cost of ownership for the 4 pound wight
penalty of an SD-8 is far, Far, FAR lower than
that of any second battery you might choose to
lug around ESPECIALLY lithium.
Bob . . .
Message 2
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Subject: | Internal Shunt in Alternator? |
A friend of mine has a maule m4 with a Franklin 220. He is restoring the pla
ne. The ammeter has never worked and when he removed the gauge, he traced on
e wire to the alternator. It was about 22 or 20 ga.
Are there aviation alternators out there with an internal shunt? I haven't h
eard of it but if not, this would be the cause of the ammeter not working.
Thanks
Justin
> On Jan 31, 2015, at 08:04, Robert L. Nuckolls, III <nuckolls.bob@aeroelect
ric.com> wrote:
>
> At 12:05 2015-01-30, you wrote:
>
> Bob,
> Thanks to you and other participants for help with my questions.
> Interesting that you are feeling so confident in the application of Li bat
teries. This is really a significant step forward in technology for small ai
rcraft.
>
> I have not said that it's a "step forward" . . . in fact,
> I have raised questions as to the economics for the transition
> to lithium. I will assert that lithium is an alternative
> ingredient that may well be an appealing recipe for success.
> I don't yet see a concise definition of 'success'.
>
> There are three separate lines of inquiry that influence the
> choice to incorporate lithium batteries into your personal
> elegant solution.
>
> Integration: It's no different than the study of how
> transistors evolved with significant milestones marked
> by the relative fragility of the PNP germanium
> transistors that first flew in airplanes. Devices later
> displaced with more robust NPN silicon. More recently,
> the power mosfet is King Silicon. EVERY evolutionary
> plateau was an improvement in performance, robustness
> and service life. However, EVERY step up required major
> changes to the circuitry and design philosophy to fully
> exploit what the new device had to offer. One could not
> simply pull out the old and plug in the new. This is
> the foundation for my distaste of popular marketing
> hype citing "lead-acid equivalency".
>
> Lithium is equivalent to nothing . . . its greatest
> advantages cannot be fully exploited without careful
> attention to just how this ingredient 'fits' into
> the recipe for success.
>
> Cost of Ownership: When Burt Rutan was putting the sharp
> pencil to the design of Voyager, weight was a critical
> consideration.
>
> He told us that it takes 5 pounds of fuel to carry
> one pound of airplane around the world. Every pound
> removed from empty weight removes 6 pounds from gross
> weight at takeoff. Nearly one gallon more fuel. One gallon
> at end of mission would carry Voyager another hundred
> miles or so. But there were prices to pay. The materials
> to build such a 'featherweight' airplane with any structural
> integrity were very expensive. Further, fuel unique mission
> requirement multiplies the weight of the airplane by 6 times
> called for a fuel tank with wings having very attractive
> l/d ratios . . . at the sacrifice of handling qualities.
> Dick Rutan confessed that the airplane scared the hell
> out of him . . . he had nightmares of dying in that
> airplane. Without the fine support of King Radio for
> an autopilot that would handle this winged beast,
> the around-the-world mission would have humanly
> impossible. Without pedantic attention to weight,
> sometimes a great cost, the mission might not have been
> possible.
>
> Risk: Properly conducted FMEA seek to study, discover,
> classify, understand and ultimately mitigate all the
> ways that the product can first, cease to preform
> intended duties as one of many players in the orchestra.
> Then, mitigate failures that put the entire system at risk for
> catastrophic collapse. It's one thing for the cello
> player to break a string . . . quite another for
> to be sneezing H1N1 into the surrounding environment.
>
> You emphasized to "operate (Lithium battery) within well established limit
s and preventative maintenance to verify integrity." Will you elaborate rega
rding how this looks with Li? You have mentioned in the past about the lack
of data from many manufacturers, and the lack of lead acid equivalency. Do y
ou feel the BMS used by EarthX is a final equilibrator here?
>
> The purveyors of lithium are the first folks to assert
> that battery management systems are always a 'good'
> idea. What ever form they take, the BMS mitigates risk
> for catastrophic failure. Just how the BMS is configured
> and applied in practice a big factor in performance, risk
> and cost of ownership. It's unreasonable and added risk
> to expect the consumer (OBAM aircraft builder) to take
> on yet another task that amounts to micro-managing the
> lithium physics. Especially when compared to the mature,
> relatively docile qualities of lead-acid. BMS may not
> be the 'final' answer to the svla vs. lithium decision
> but certainly a major consideration.
>
> An this still leaves the question I've asked and
> nobody has come forward to answer, "What are the
> numbers . . . how will the smaller weight and volume
> numbers manifest in the performance and utility of
> say, an RV7 presently fitted wity a PC680? Shorter
> takeoffs? Higher mountains to challenge, cleared
> out space to store your sandwiches?
>
> Boeing's considerations for battery weight were but one
> component in a HUGE model of cost/benefit ratios. The numbers
> they considered enticed them to spend $millions$ in making
> the switch to lithium. What are YOUR numbers?
>
>
> The advanced EFII system I have been evaluating may be a bit too far up t
he ladder for my project, as you pointed out. The 10 ampere requirement quot
ed was per email from manufacturer and is for both the fuel and ignition sys
tems. Majority apparently consumed by the fuel pump - one of two runs at a t
ime to pressurize a fuel rail.
>
> Yes . . . and I've heard 'up and running' numbers on
> that system 'quoted' from 6 to 10 amps . . . but I have
> yet to discover published data that speaks to the real
> energy requirements for this system.
>
> People may snicker at my insistence that the purveyors of
> lithium come forth with "all the numbers" . . . like
> Hawker/Enersys and virtually all contemporaries. But as
> Lord Kelvin often opined, "without the numbers you have
> barely scratched the surface of the science." I will build
> on that sentiment by suggesting that the decision should not
> devolve to preferring Big Macs just because they taste good
> without knowing how they integrate into the energy
> conversion/management system of a very complex machine.
> Questions that remain undiscovered, unasked, unanswered
> and/or ill-considered may bring the system down no matter
> how good the product tasted.
>
> EFII "owes" you the same quality of numbers that we expect
> from Rotax, AeroVoltz, Icom, Smiley Jack's Prop Shop
> . . . or anybody else that wants to play honorably and capably
> in this sandbox.
>
> Anyway, I am currently favoring a pullback to a set of P Mags, mechanical f
uel injection, a single Li battery with a small detached back up, and a sing
le alternator. This set up should perform similarly in practical terms, and b
e very reliable and light.
>
> Sounds like a considered move . . . what now are your
> electrical system numbers insuring comfortable termination
> of flight limited only by fuel aboard?
>
> Are you going to have a vacuum pump? Why waste a
> perfectly good energy source by covering the pump
> pad with a plate of aluminum? After nearly 20 years
> of sifting the numbers, FMEA scenarios, costs of
> ownership and performance, I suggest that Figure Z-13/8
> is as near 'perfection' for flight system reliability
> . . . assuming of course that you don't burden it with
> an 120 watt engine support demands.
>
> You speak of two batteries . . . why? One or both lithium?
> Can you share your FMEA and cost of ownership reasoning?
> Exactly how will that savings of wight manifest in performance
> or utility of your airplane . . . and at what cost of
> hours to integrate and maintain performance at minimum
> levels throughout the service life of the battery?
>
> Z-13/8 will keep your panel lit and allow you to
> run any battery until it won't crank the engine any
> more. The cost of ownership for the 4 pound wight
> penalty of an SD-8 is far, Far, FAR lower than
> that of any second battery you might choose to
> lug around ESPECIALLY lithium.
>
> Bob . . .
>
>
>
==========================
=========
==========================
=========
==========================
=========
==========================
=========
>
Message 3
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Subject: | Re: Internal Shunt in Alternator? |
At 15:16 2015-01-31, you wrote:
>A friend of mine has a maule m4 with a Franklin 220. He is restoring
>the plane. The ammeter has never worked and when he removed the
>gauge, he traced one wire to the alternator. It was about 22 or 20 ga.
>
>Are there aviation alternators out there with an internal shunt? I
>haven't heard of it but if not, this would be the cause of the
>ammeter not working.
>
> Thanks
>
>Justin
There were a few, less than elegant ammeter
installations that relied on copper wiring
resistance to stand-in for a real shunt.
The fact that one wire did go to the alternator
(I guessing b-lead terminal) I suspect the
other end is tied to the alternator-side of
the b-lead breaker. Hence, voltage drop more
or less proportional to b-lead current could
be impressed on an instrument for display.
Is he interested in getting the ammeter to
work? He might send it to me and I'll test
and quantify the instrument itself . . . we
could go from there to determine the most
practical way to get it up and running again.
Baring that, encourage him to install active
notification of low voltage . . . a flashing
light thingy. That's about 10x more useful than
any ammeter.
Bob . . .
Message 4
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Subject: | Electrical System with Dual Batteries & Brownout Prevent |
Joe,
A couple of things you probably have already considered and discarded
(or have omitted for simplicity):
No over voltage protection is shown.
Perhaps feed the bilge pump switch from main bus, or otherwise ensure
it can be easily shut off when turning off master switches to avoid
accidentally draining the battery.
As shown, there is no way to operate the Avionics and Engine bus as an
E-Bus without powering the Main bus.
That said, I cannot come up with an elegant switching solution to make
that happen.
One option is an additional switch that operates both relays, but in
an emergency, it would be easy to flip off the master switches before
turning on the E-Bus switch. If this is an electrically dependent
engine with the ignition powered from the Avionics and Engine bus,
that would lead to a pretty scary moment.
Another option is to use 2-10 switches and use the center position for
the Avionics and Engine bus, although again, in an emergency, the
tendency might be to turn those switches fully off, since that is the
habit ingrained at the end of every flight.
A totally different approach, what about this ? Feed the coils of the
relays from the Avionics and Engine bus. So when either contactor is
engaged, both relays are engaged and stay engaged when the masters are
shut off. Interrupt the feed to the relays at the end of the flight
with a normally on momentary switch marked Engine Shutdown. This
doesn't give you the ability to manually engage the Avionics and
Engine bus before flight to do clearance delivery and configure
avionics (you could using a 2-50 switch), but you won't shut off the
master switches and accidentally turn off the electronic ignition in
flight.
If you have previously posted details, I missed them. Are you
planning to connect an electrically dependent engine to the Avionics
and Engine bus ? Perhaps consider a battery bus for the critical
items ?
Bob can confirm, but perhaps there are situations, like a shorted cell
in a battery that would prevent the alternator charging the good
battery. In that case, perhaps it is better to add a second
alternator and keep the cross feed open during flight. This
complicates the pilot's job a lot and after mulling this over for
quite a while, I ended up going with Z13-8 for my plane.
Depending how far you are from civilization when the single alternator
fails, perhaps a second alternator is a good idea ?
Hopefully there is something useful to you in the above.
Jeff Page
Dream Aircraft Tundra #10
> Time: 06:45:38 PM PST US
> Subject: AeroElectric-List: Electrical System with Dual Batteries &
> Brownout Prevent
> From: "user9253" <fransew@gmail.com>
>
>
> Attached is a diagram that I drew of an electrical system with two
> engine-cranking
> batteries and brownout prevention. It is intended for a seaplane that will
> fly into remote lakes. Either battery can crank the engine. One of
> the batteries
> will run a bilge pump. If the engine is cranked using only one battery,
> then the other battery will provide 12 volts to avionics to prevent brownout.
> The electrically dependent engine will be powered by the same bus as
> the avionics.
> With multiple current paths through two contactors and two relays, the
> chances of this bus losing power are slim. Good workmanship will
> prevent short
> circuits.
> Go ahead and point out any faults with this diagram or give
> suggestions. You
> will not hurt my feelings. I want to fix any shortcomings or design errors.
> I used Bob N's Z-19/RB as a staring point, although you might not
> see any resemblance.
> Joe
>
> --------
> Joe Gores
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=437846#437846
>
>
> Attachments:
>
> http://forums.matronics.com//files/dual_bat_brownout_prevention__202.pdf
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