Today's Message Index:
----------------------
1. 08:13 AM - Re: Essential Bus question (Robert L. Nuckolls, III)
2. 08:42 AM - Re: Essential Bus question (Robert L. Nuckolls, III)
3. 08:49 AM - Re: 12V to 9V converter (Robert L. Nuckolls, III)
4. 09:32 AM - Re: Essential Bus question (Tim Andres)
5. 10:47 AM - Re: Essential Bus question (Robert L. Nuckolls, III)
6. 02:34 PM - Re: Essential Bus question (Jeff Luckey)
7. 03:39 PM - Analyze This (Jeff Luckey)
8. 03:39 PM - Re: Essential Bus question (Robert L. Nuckolls, III)
9. 04:14 PM - Re: Essential Bus question (Tim Andres)
10. 04:14 PM - Re: Essential Bus question (Kelly McMullen)
11. 05:11 PM - Re: Essential Bus question (Robert L. Nuckolls, III)
12. 05:57 PM - Re: Analyze This (Robert L. Nuckolls, III)
13. 07:44 PM - Re: Analyze This (Jeff Luckey)
Message 1
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| Subject: | Re: Essential Bus question |
At 08:25 PM 1/31/2014, you wrote:
My first question would be why add the complexity of a second
electrical system, when virtually all situations . . .
Define "all situations" . . . the term is non-
quantified/qualified. When we're designing a
TC aircraft, EVERY situation needs to be articulated
in the design documents along with the plan-B, C, . . .
or Z that mitigates that situation. Then we have
to go TEST every one of those plans to demonstrate
compliance with design goals.
. . . can be handled by either backup battery for EFIS, ship's
battery or just plain old magnetos.
For OBAM aircraft it's a function of design goals built upon
the pilot's skills, maintenance protocols, airplane capabilities
and anticipated missions. Obviously, the manner in which
one might outfit a Kitfox can depart greatly from the
way you would craft an LAIV-P. At the same time, the
builder of an RV-6 in the Pacific NW (Lots of clouds
all the time) who travels a lot might have a more
sophisticated system than another builder who intends
to use is LAIV only in day VMC but wants the
speed, ability to hop the occasional mountain range
and air conditioning.
This litany of potential "situations" offers
a brief peek into the value of having design
goals synchronized to the end-use.
Production aircraft tend to have cookie-cutter
approaches to system architecture . . . because
the designers can only hypothesize greatest risk
situations for the targeted customer then address
those hypotheses within the framework of the
impediments to creativity imposed by the FARS.
We on the List have a clean sheet of paper
for the beginning of every project. The Z-figures
are intended to offer a sort of "Cliff's Notes"
on architectures that span the spectrum of
possibilities. Some builders have put Z-14
into their 2 place RV's at no small penalty
for cost and weight . . . but find comfort
in not having to go through the very non-
trivial exercise of optimizing their decision.
There ARE LAIV-P aircraft flying with one
battery, one alternator, and backup batteries
sprinkled over the panel and perhaps some
more in the flight bag.
Its unlikely that either builder has tested
available failure response plans against his/her
perceptions of capability in the Plan-B
hardware.
Given the decreasing failure rates of modern
electro-whizzies, it's unlikely that either
of the pilots in the last two examples will
have a 'dark-n-stormy night' story to write
up for Flying Magazine.
Bob . . .
Message 2
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| Subject: | Re: Essential Bus question |
At 01:53 PM 1/31/2014, you wrote:
>
>My RV-6 has been flying 12 years now with an electrical system based
>on the Z diagrams. Now I am assisting my wife complete her RV-7
>electrical system. She has chosen to use the VPX Pro unit and wants
>to incorporate a "backup" source of power for clearances, engine
>start, and "endurance" (if the VPX box were to quit).
Okay, you're plagued with the same litany of concerns
that arise from lack of confidence in your present
'vision' for how this system should evolve.
>
>The circuit that we are considering uses a bridge diode that would
>allow the main battery to supplement the "backup" battery for
>increased endurance. Since I have not seen this variation before,
>there must be a "gotcha" that I haven't found. Attached is a
>picture of the basic circuit. Any suggestions and/or comments would
>be appreciated.
Read through the posting I made a few minutes ago
and then consider a list of design goals that are
based on . . .
(1) How will this airplane be used? Do you
anticipate long legs of travel at night over
unfriendly terrain?
(2) Are you anticipating more than a tiny
percentage of approaches to landing to be
in IMC?
(3) Do you plan to carry the ultimate in
backup reliability in your flight bag?
http://tinyurl.com/d5mrjgh
This is the stuff I recommend for folks like
me who only rent airplanes . . . but if
it were my airplane, those items would still
be with me. In fact, I've not turned on a
VOR or ADF in 15 years . . . nor have I used
a panel mounted GPS . . . but that's another
story.
(4) Are your skill sets going to be honed
to the levels necessary for low risk
implementation of the hardware you plan to install?
It's entirely possible to have an airplane
decked out to the window-sills with goodies
only to have A pilot become the weak link
in the chain.
http://tinyurl.com/kb2zr8m
I've flown with pilots who were quite proud
of all those dials, switches and knobs on
the panel who never flew more IFR than to
keep their ticket current. The greatest
risk for bending their airplane was not
rooted failure of hardware.
Keep in mind that 2x the hardware is 2x
the probability of failure. Got some more
batteries scattered around the airplane
. . . guess what . . . now you're running
a clinic for batteries upon which you believe
you're building a 'dependable' system.
Commodity items like batteries are like house plants.
Just because you have two of them does not mitigate
the need for knowledgeable preventative
maintenance but it DOES double the maintenance
$time$.
So before we spend a lot of time refining
the work-arounds for hypothesized failures,
let's look at the big picture and size the
solutions to realistic risks having the
greatest probability of presentation.
Then you're ready to sift solutions for those
having the lowest cost of ownership, weight
penalties on the aircraft and taxation of
your skill sets.
Bob . . .
Message 3
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| Subject: | Re: 12V to 9V converter |
>Bob, I have an old (30+ years) Hall variometer that I want to put in
>my trike. It's powered by 9V batteries so it seems an easy enough
>project to use a converter to power it off the dynamo on the HKS
>engine. 2 amps should be more than enough output. There are quite a
>few vendors on eBay that offer them for $2 or so. Do you have any
>favorite vendors for this kind of thing?
>
>Rick Girard
What kind of 9v batteries? These things?
Emacs!
More than one? How many and do you KNOW
they are in parallel and not series for
+/- supply to the electronics?
Bob . . .
Message 4
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| Subject: | Re: Essential Bus question |
I would just add a simple Brown out 7ah Alarm battery/Aux bus charged thru a Schottky
diode and maybe a resistor is very simple & cheap to do. A lot of equipment
now comes with multiple diode isolated power inputs making it easy.
This allows flight plan entry and clearance requests before start up without draining
the main battery, keeps the GPS/NAV/COM and EFIS from rebooting when cranking
the engine, and provides maybe 20-30 minutes of extra time to get back
on the ground.
Weight/cost is about $35 and 5 lbs. cheaper than a factory backup, which only powers
one item.
Tim
> On Feb 2, 2014, at 8:39 AM, "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
wrote:
>
>
> At 01:53 PM 1/31/2014, you wrote:
>>
>> My RV-6 has been flying 12 years now with an electrical system based on the
Z diagrams. Now I am assisting my wife complete her RV-7 electrical system.
She has chosen to use the VPX Pro unit and wants to incorporate a "backup" source
of power for clearances, engine start, and "endurance" (if the VPX box were
to quit).
>
> Okay, you're plagued with the same litany of concerns
> that arise from lack of confidence in your present
> 'vision' for how this system should evolve.
>>
>> The circuit that we are considering uses a bridge diode that would allow the
main battery to supplement the "backup" battery for increased endurance. Since
I have not seen this variation before, there must be a "gotcha" that I haven't
found. Attached is a picture of the basic circuit. Any suggestions and/or
comments would be appreciated.
>
> Read through the posting I made a few minutes ago
> and then consider a list of design goals that are
> based on . . .
>
> (1) How will this airplane be used? Do you
> anticipate long legs of travel at night over
> unfriendly terrain?
>
> (2) Are you anticipating more than a tiny
> percentage of approaches to landing to be
> in IMC?
>
> (3) Do you plan to carry the ultimate in
> backup reliability in your flight bag?
>
> http://tinyurl.com/d5mrjgh
>
> This is the stuff I recommend for folks like
> me who only rent airplanes . . . but if
> it were my airplane, those items would still
> be with me. In fact, I've not turned on a
> VOR or ADF in 15 years . . . nor have I used
> a panel mounted GPS . . . but that's another
> story.
>
> (4) Are your skill sets going to be honed
> to the levels necessary for low risk
> implementation of the hardware you plan to install?
> It's entirely possible to have an airplane
> decked out to the window-sills with goodies
> only to have A pilot become the weak link
> in the chain.
>
> http://tinyurl.com/kb2zr8m
>
> I've flown with pilots who were quite proud
> of all those dials, switches and knobs on
> the panel who never flew more IFR than to
> keep their ticket current. The greatest
> risk for bending their airplane was not
> rooted failure of hardware.
>
> Keep in mind that 2x the hardware is 2x
> the probability of failure. Got some more
> batteries scattered around the airplane
> . . . guess what . . . now you're running
> a clinic for batteries upon which you believe
> you're building a 'dependable' system.
>
> Commodity items like batteries are like house plants.
> Just because you have two of them does not mitigate
> the need for knowledgeable preventative
> maintenance but it DOES double the maintenance
> $time$.
>
> So before we spend a lot of time refining
> the work-arounds for hypothesized failures,
> let's look at the big picture and size the
> solutions to realistic risks having the
> greatest probability of presentation.
>
> Then you're ready to sift solutions for those
> having the lowest cost of ownership, weight
> penalties on the aircraft and taxation of
> your skill sets.
>
>
> Bob . . .
>
>
>
>
Message 5
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| Subject: | Re: Essential Bus question |
At 11:31 AM 2/2/2014, you wrote:
>
>I would just add a simple Brown out 7ah Alarm battery/Aux bus
>charged thru a Schottky diode and maybe a resistor is very simple &
>cheap to do. A lot of equipment now comes with multiple diode
>isolated power inputs making it easy.
>This allows flight plan entry and clearance requests before start up
>without draining the main battery, keeps the GPS/NAV/COM and EFIS
>from rebooting when cranking the engine, and provides maybe 20-30
>minutes of extra time to get back on the ground.
>Weight/cost is about $35 and 5 lbs. cheaper than a factory backup,
>which only powers one item.
>
>Tim
Good data points. Let us consider the premises
underlying the evolution of Figure Z-07
http://tinyurl.com/my9u3ud
this shows a two battery/single alternator system
for an electrically dependent engine. This
exercise in 'electron gazing' grew out of Fred's
project already fitted with a EXP-Bus. I could
see a way to accommodate Fred's initial design
goals for two batteries with a simple mod to
the EXP-Bus . . . but I could see an alternative
to Z-19 evolving from the deliberations . . .
hence Z-07.
Off in the distance, I think I see a single-battery
variant of this architecture but that's possible
only after we get real energy requirements data
. . . and further refine the operating philosophy
for the system. Tim's words raise useful questions
that go directly to deliberations for sizing risks
in a single-battery design.
Where is it written or demonstrated that having
the ship's processors 'reboot' is a bad thing?
Under what operating scenarios is it useful/necessary
minimize the time between the glass being awake
and reaching the end of the runway just prior
to engine run-up?
I recall some stories about the Blue-Mountain
systems (hard drives?) taking perhaps 90
seconds to wake up . . . but when was the
last time you were ready to check mags less
than, say 3-4 minutes after engine startup?
I've reviewed as many of the airports I've
visited that I can remember. I cannot recall
any departure where engine run-up was accomplished
for before the oil was warmed up a bit and I
had taxied from parking to the run-up stand,
certainly 4 minutes, sometimes 10. I think
it took 15 minutes to get out of KCI once.
. . . the check list belongs to YOU . . . you
can adjust sequences of events to fit hardware.
Let us consider "draining the main battery"
for the purposes of gathering the ATIS data
and getting a clearance delivery. Suppose the
e-bus runs 5A and the exercise takes 3 minutes.
12v x 5a x 60s x 3m = 10,800 watt-seconds.
Cranking the engine 12v x 200a x 10s = 24,000
watt-seconds. What does the battery hold?
12v x 5a x 60s x 120m = 432,000 watt-seconds.
Okay, you used up 34,800 watt-seconds before
the engine was lit for 35K/432K or 8 percent
of the battery's capacity. If you're targeting
80% of new capacity for banishing your battery
to kiddie-car duty, then the last flight
will tax the battery to 10% of available
capacity.
The above analysis is a first order estimate
and does not take into account vagaries of
temperature and internal impedances of the
battery but it's in the right church if not
in the right pew.
Whats is the return on investment for 5 more
pounds of battery and two batteries to maintain
instead of one?
The value of this . . . or even more detailed
analysis presumes that you KNOW what the
drains are and what the battery's capabilities
are after accounting for aforementioned
vagaries AND targeted end of life decisions.
Bob . . .
Message 6
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| Subject: | Re: Essential Bus question |
my comments in larger font...=0A=0A-Jeff=0A=0A=0A=0A_______________________
_________=0A From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com
>=0ATo: aeroelectric-list@matronics.com =0ASent: Sunday, February 2, 2014 1
0:47 AM=0ASubject: Re: AeroElectric-List: Essential Bus question=0A =0A=0A-
.bob@aeroelectric.com>=0A=0AAt 11:31 AM 2/2/2014, you wrote:=0A> --> AeroEl
ectric-List message posted by: Tim Andres <tim2542@sbcglobal.net>=0A> =0A>
I would just add a simple Brown out 7ah Alarm battery/Aux bus charged thru
a Schottky diode and maybe a resistor is very simple & cheap to do. A lot o
f equipment now comes with multiple diode isolated power inputs making it e
asy.=0A> This allows flight plan entry and clearance requests before start
up without draining the main battery,- keeps the GPS/NAV/COM and EFIS fro
m rebooting when cranking the engine, and provides maybe 20-30 minutes of e
xtra time to get back on the ground.=0A> Weight/cost is about $35 and 5 lbs
. cheaper than a factory backup, which only powers one item.=0A> =0A> Tim
=0A=0A- Good data points. Let us consider the premises=0A- underlying
the evolution of Figure Z-07=0A=0Ahttp://tinyurl.com/my9u3ud=0A=0A- thi
s shows a two battery/single alternator system=0A- for an electrically d
ependent engine. This=0A- exercise in 'electron gazing' grew out of Fred
's=0A- project already fitted with a EXP-Bus. I could=0A- see a way t
o accommodate Fred's initial design=0A- goals for two batteries with a s
imple mod to=0A- the EXP-Bus . . . but I could see an alternative=0A-
to Z-19 evolving from the deliberations . . .=0A- hence Z-07.=0A=0A-
Off in the distance, I think I see a single-battery=0A- variant of this
architecture but that's possible=0A- only after we get real energy requ
irements data=0A- . . . and further refine the operating philosophy=0A
- for the system. Tim's words raise useful questions=0A- that go dire
ctly to deliberations for sizing risks=0A- in a single-battery design.
=0A=0A- Where is it written or demonstrated that having=0A- the ship'
s processors 'reboot' is a bad thing?=0A=0AOK, let me write it here:=0AWatc
hing the Garmin 430 in my Cherokee re-boot after engine start is very incon
venient. Is it catastrophic? No.- Are there work-arounds? Certainly.- I
t's just a pain in the @ss.- In an experimental w/ all glass, it would be
even more annoying.=0A=0ANow that I'm designing the electrical system for
my RV-7A, I'm certainly want a design where that does not happen.- This i
s one of the reasons people like us build our own airplanes - we get to eng
ineer-out those little annoyances that we just have to put up with in certi
fied airplanes.=0A=0A=0A- Under what operating scenarios is it useful/ne
cessary=0A- minimize the time between the glass being awake=0A- and r
eaching the end of the runway just prior=0A- to engine run-up?=0A=0A-
I recall some stories about the Blue-Mountain=0A- systems (hard drives?
) taking perhaps 90=0A- seconds to wake up . . . but when was the=0A-
last time you were ready to check mags less=0A- than, say 3-4 minutes a
fter engine startup?=0A=0A- I've reviewed as many of the airports I've
=0A- visited that I can remember. I cannot recall=0A- any departure w
here engine run-up was accomplished=0A- for before the oil was warmed up
a bit and I=0A- had taxied from parking to the run-up stand,=0A- cer
tainly 4 minutes, sometimes 10. I think=0A- it took 15 minutes to get ou
t of KCI once.=0A=0AAll true but, there are also thousands of quiet little
airports where you can depart as quickly as you want to=0A=0A- . . . the
check list belongs to YOU . . . you=0A- can adjust sequences of events
to fit hardware.=0A=0A- Let us consider "draining the main battery"=0A
- for the purposes of gathering the ATIS data=0A- and getting a clear
ance delivery. Suppose the=0A- e-bus runs 5A and the exercise takes 3 mi
nutes.=0A- 12v x 5a x 60s x 3m = 10,800 watt-seconds.=0A- Cranking
the engine 12v x 200a x 10s = 24,000=0A- watt-seconds. What does the b
attery hold?=0A- 12v x 5a x 60s x 120m = 432,000 watt-seconds.=0A=0A
- Okay, you used up 34,800 watt-seconds before=0A- the engine was lit
for 35K/432K or 8 percent=0A- of the battery's capacity. If you're targ
eting=0A- 80% of new capacity for banishing your battery=0A- to kiddi
e-car duty, then the last flight=0A- will tax the battery to 10% of avai
lable=0A- capacity.=0A=0A- The above analysis is a first order estima
te=0A- and does not take into account vagaries of=0A- temperature and
internal impedances of the=0A- battery but it's in the right church if
not=0A- in the right pew.=0A=0A- Whats is the return on investment fo
r 5 more=0A- pounds of battery and two batteries to maintain=0A- inst
ead of one?=0A=0A- The value of this . . . or even more detailed=0A-
analysis presumes that you KNOW what the=0A- drains are and what the bat
tery's capabilities=0A- are after accounting for aforementioned=0A- v
=================
Message 7
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Listers,=0A=0AAttached find a schematic (some people call them ladder diagr
ams) of a design for the electrical system for my RV-7A.- Below is a list
of design goals, pros and cons. Please take a look and provide engineering
feedback.=0A=0ATIA=0A=0A=0AElectrical Systems Design Goals:=0A1. fault tol
erant - able to tolerate failure of any single component and fly for 45 min
.=0A2. easy to operate=0A3. no avionics brown-out on engine start=0A4. easy
to repair=0A5. comprised of standard, readily-available components =0A6. c
ost effective=0A=0A=0APros:=0A1. simplified operation - only 2 master switc
hes=0A2. simplified design - single buss=0A=0A3. no brown-out on engine sta
rt=0A4. automatic fail-over - no pilot interaction required; avionics won't
reset=0A=0A--- In the event a battery system suffers a failure, eith
er an open circuit or a ground fault, the faulty=0A--- system simply
stops providing power to the buss and the remaining good system continues t
o =0A=0A--- provide electricity without interruption.=0A=0A=0ACons:
=0A1. buss-isolation power diodes may require heat sinks=0A2. some energy w
asted as heat thru power diodes
Message 8
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| Subject: | Re: Essential Bus question |
OK, let me write it here:
Watching the Garmin 430 in my Cherokee re-boot after engine start is
very inconvenient.
Stop-watch that for me some time. I'd really
like to have a number on this widely discussed
but never quantified driver of design goals.
Is it catastrophic? No. Are there work-arounds? Certainly. It's
just a pain in the @ss.
In an experimental w/all glass, it would be even more annoying.
Now that I'm designing the electrical system for my RV-7A, I'm
certainly want a design
where that does not happen. This is one of the reasons people like
us build our own
airplanes - we get to engineer-out those little annoyances that we just have to
put up with in certified airplanes.
Then by all means do so. It's your airplane and your
design goals. The question wasn't whether or not you
wanted to do a particular thing, it was an invitation
explore why you wanted to do it . . . hopefully for reasons
firmly of your own choosing and not 'just because'
hangar lore and legacy traditions dictated it.
Brownout batteries have been discussed her on the list often
for several years an even illustrated one approach
in Z-10/8
http://tinyurl.com/7ro5yuc
All true but, there are also thousands of quiet little airports where you can
depart as quickly as you want to
Yup . . . there are. If a significant percentage
of your departures are so expeditious that
boot time on the glass becomes an impediment,
then you have an element of fact that drives
a different design goal.
I'm trying head off any notions that just because
one is considering a glass cockpit that a brownout
battery is recommended . . . it comes with a price in
weight and costs of ownership that may add little
or no value.
Bob . . .
Message 9
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| Subject: | Re: Essential Bus question |
Not to argue your points Bob, and I agree simple is often better, but I would just
add that I don't want to wait 20 seconds for the screens to reboot after engine
start as my engine data is there also and I want see oil pressure etc right
away.
And I much prefer to enter a lengthy flight plan with the prop off as my attention
will be focused inside the plane, I'll admit on occasion I've looked up from
the panel and discovered the plane moving. My flight plan will then be lost
when I then crank the engine, unless I save it to memory, which I won't unless
I'm using it again.
And sometimes I take off with a hot engine, I'd rather not sit with the already
hot engine running in the summer heat while I enter several waypoints in the
Garmin.
To me it's worth the 5lbs for the convenience, and the cost is easily overcome
in fuel not burned.
The beauty of EAB, built what you want, then live with your decisions.
Tim
> On Feb 2, 2014, at 10:47 AM, "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
wrote:
>
>
> At 11:31 AM 2/2/2014, you wrote:
>>
>> I would just add a simple Brown out 7ah Alarm battery/Aux bus charged thru a
Schottky diode and maybe a resistor is very simple & cheap to do. A lot of equipment
now comes with multiple diode isolated power inputs making it easy.
>> This allows flight plan entry and clearance requests before start up without
draining the main battery, keeps the GPS/NAV/COM and EFIS from rebooting when
cranking the engine, and provides maybe 20-30 minutes of extra time to get back
on the ground.
>> Weight/cost is about $35 and 5 lbs. cheaper than a factory backup, which only
powers one item.
>>
>> Tim
>
> Good data points. Let us consider the premises
> underlying the evolution of Figure Z-07
>
> http://tinyurl.com/my9u3ud
>
> this shows a two battery/single alternator system
> for an electrically dependent engine. This
> exercise in 'electron gazing' grew out of Fred's
> project already fitted with a EXP-Bus. I could
> see a way to accommodate Fred's initial design
> goals for two batteries with a simple mod to
> the EXP-Bus . . . but I could see an alternative
> to Z-19 evolving from the deliberations . . .
> hence Z-07.
>
> Off in the distance, I think I see a single-battery
> variant of this architecture but that's possible
> only after we get real energy requirements data
> . . . and further refine the operating philosophy
> for the system. Tim's words raise useful questions
> that go directly to deliberations for sizing risks
> in a single-battery design.
>
> Where is it written or demonstrated that having
> the ship's processors 'reboot' is a bad thing?
> Under what operating scenarios is it useful/necessary
> minimize the time between the glass being awake
> and reaching the end of the runway just prior
> to engine run-up?
>
> I recall some stories about the Blue-Mountain
> systems (hard drives?) taking perhaps 90
> seconds to wake up . . . but when was the
> last time you were ready to check mags less
> than, say 3-4 minutes after engine startup?
>
> I've reviewed as many of the airports I've
> visited that I can remember. I cannot recall
> any departure where engine run-up was accomplished
> for before the oil was warmed up a bit and I
> had taxied from parking to the run-up stand,
> certainly 4 minutes, sometimes 10. I think
> it took 15 minutes to get out of KCI once.
>
> . . . the check list belongs to YOU . . . you
> can adjust sequences of events to fit hardware.
>
> Let us consider "draining the main battery"
> for the purposes of gathering the ATIS data
> and getting a clearance delivery. Suppose the
> e-bus runs 5A and the exercise takes 3 minutes.
> 12v x 5a x 60s x 3m = 10,800 watt-seconds.
> Cranking the engine 12v x 200a x 10s = 24,000
> watt-seconds. What does the battery hold?
> 12v x 5a x 60s x 120m = 432,000 watt-seconds.
>
> Okay, you used up 34,800 watt-seconds before
> the engine was lit for 35K/432K or 8 percent
> of the battery's capacity. If you're targeting
> 80% of new capacity for banishing your battery
> to kiddie-car duty, then the last flight
> will tax the battery to 10% of available
> capacity.
>
> The above analysis is a first order estimate
> and does not take into account vagaries of
> temperature and internal impedances of the
> battery but it's in the right church if not
> in the right pew.
>
> Whats is the return on investment for 5 more
> pounds of battery and two batteries to maintain
> instead of one?
>
> The value of this . . . or even more detailed
> analysis presumes that you KNOW what the
> drains are and what the battery's capabilities
> are after accounting for aforementioned
> vagaries AND targeted end of life decisions.
>
>
> Bob . . .
>
>
>
>
Message 10
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| Subject: | Re: Essential Bus question |
Virtually all glass have their own light weight backup batteries so do
not have startup brown out issues unless no backup battery is installed.
I see very little value in being able to turn on GPS prior to start.
While one needs engine instrumentation prior to and during start, one
does not need avionics on.
Of course newer avionics that allow faster input of flight plans than
the 430 help, if that is the reason for turning on 430 before start.
On 2/2/2014 4:39 PM, Robert L. Nuckolls, III wrote:
>
>
> Brownout batteries have been discussed her on the list often
> for several years an even illustrated one approach
> in Z-10/8
>
> http://tinyurl.com/7ro5yuc
>
>
> All true but, there are also thousands of quiet little airports where
> you can
> depart as quickly as you want to
>
> Yup . . . there are. If a significant percentage
> of your departures are so expeditious that
> boot time on the glass becomes an impediment,
> then you have an element of fact that drives
> a different design goal.
>
> I'm trying head off any notions that just because
> one is considering a glass cockpit that a brownout
> battery is recommended . . . it comes with a price in
> weight and costs of ownership that may add little
> or no value.
>
>
> Bob . . .
>
>
Message 11
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| Subject: | Re: Essential Bus question |
At 06:14 PM 2/2/2014, you wrote:
>
>Not to argue your points Bob, and I agree simple is often better,
>but I would just add that I don't want to wait 20 seconds for the
>screens to reboot after engine start as my engine data is there also
>and I want see oil pressure etc right away.
Yeah . . . that's an old saw that has been around
since the Curtis Jenny . . . when sheared oil pump
shafts were relatively common . . . along with a
host of other ills associated with vintage engines.
I've never encountered a pilot who's oil pump died
at startup. I've flown lots of airplanes in cold
weather that didn't show any pressure for 30-45
seconds after start.
>And I much prefer to enter a lengthy flight plan with the prop off
>as my attention will be focused inside the plane, I'll admit on
>occasion I've looked up from the panel and discovered the plane
>moving. My flight plan will then be lost when I then crank the
>engine, unless I save it to memory, which I won't unless I'm using it again.
>And sometimes I take off with a hot engine, I'd rather not sit with
>the already hot engine running in the summer heat while I enter
>several waypoints in the Garmin.
You mean its stored waypoints go away during
reboot?
>
>To me it's worth the 5lbs for the convenience, and the cost is
>easily overcome in fuel not burned.
>The beauty of EAB, built what you want, then live with your decisions.
Absolutely. But why 5#? What did Eric decide about
his brown-out eliminator? Perhaps we still need
to refine the electronic bus-booster idea . . . it
weights a few ounces and has no periodic maintenance
requirements. Of course, a battery used only for
brownout protection can be run until it dies . . .
as long as the pilot doesn't included it in his/her
calculations for battery only endurance.
Bob . . .
Message 12
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| Subject: | Re: Analyze This |
At 05:38 PM 2/2/2014, you wrote:
>Listers,
>
>Attached find a schematic (some people call them ladder diagrams) of
>a design for the electrical system for my RV-7A. Below is a list of
>design goals, pros and cons. Please take a look and provide
>engineering feedback.
The alternator's b-lead is two diode-drops
removed from the regulator bus sense lead so
expect the b-lead to run 2-drops higher voltage
than the regulator's set-point. With the battery
tapped in between the two diodes, you'll want to
adjust the regulator for a BATTERY voltage of
14.2V
This will peg the b-lead at 14.2+diodeV and
the bus at 14.2-diodeV.
Current limiters are not generally recommended
or demonstrated as useful in battery feeders.
Bob . . .
Message 13
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| Subject: | Re: Analyze This |
=0A=0A=0A=0A________________________________=0A From: "Robert L. Nuckolls,
III" <nuckolls.bob@aeroelectric.com>=0ATo: aeroelectric-list@matronics.com
=0ASent: Sunday, February 2, 2014 5:56 PM=0ASubject: Re: AeroElectric-List:
Nuckolls, III" <nuckolls.bob@aeroelectric.com>=0A=0AAt 05:38 PM 2/2/2014, y
ou wrote:=0A> Listers,=0A> =0A> Attached find a schematic (some people call
them ladder diagrams) of a design for the electrical system for my RV-7A.
- Below is a list of design goals, pros and cons. Please take a look and
provide engineering feedback.=0A=0A- The alternator's b-lead is two diode
-drops=0A- removed from the regulator bus sense lead so=0A- expect the
b-lead to run 2-drops higher voltage=0A- than the regulator's set-point.
With the battery=0A- tapped in between the two diodes, you'll want to=0A
- adjust the regulator for a BATTERY voltage of=0A- 14.2V=0A=0A- This
will peg the b-lead at 14.2+diodeV and=0A- the bus at 14.2-diodeV.=0A=0A
Roger that=0A=0A- Current limiters are not generally recommended=0A- or
demonstrated as useful in battery feeders.=0A=0AIf the prove to be problem
atic, it is very easy to bypass them=0A=0Athanks bob=0A=0A=0A- Bob . . .
=========================0A
===================
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