Today's Message Index:
----------------------
1. 08:13 AM - Re: B: Avoiding power interrupts (Robert L. Nuckolls, III)
2. 09:14 AM - Re: 24V Starter & 12V System (Robert L. Nuckolls, III)
3. 09:38 AM - Re: alternator testing (Robert L. Nuckolls, III)
4. 10:30 AM - IC A23 external antenna adapter (Charlie Brame)
5. 02:38 PM - Re: 24V Starter & 12V System (Jim and Lucy)
6. 08:38 PM - Z13 with B&C Alt/Reg combination ? (Bill Schlatterer)
Message 1
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| Subject: | Re: B: Avoiding power interrupts |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
At 11:49 AM 7/9/2005 -0400, you wrote:
>Good morning Mr. Nuckolls
>Thank you for a very helpful note
>
>GIVEN THAT: We are wiring our aircraft in a way that will allow both
>batteries to be in parallel simply by turning them both on. We will also
>have the option to take either off line in case of failure ....they
>sometimes fail by shorting internally resulting in a load to the system
Define "sometimes" . . .
Shorted cells in a flooded battery were fairly common in the
1950s . . . flooded cells typical in automobiles had 'bilges'
below the stack of plates in each cell. These were collection
spaces for active material flaking off the plates of an aging
battery. This always happens well into the service life of
the battery. There are two things that make this a non-issue
today and particularly in airplanes:
(1) VRSLA batteries of today stack the plates together
very tightly in a sandwich of lead grids and fiberglas sheets.
Some designs (like Concord) ADD a porous plastic bag over the
negative plate IN addition to the fiberglas mats which hold
the electrolyte. Cells in these batteries don't short.
(2) Airplane batteries should be monitored for useful capacity
and replaced when they fall below some value as determined by
(a) your endurance mode load analysis and (b) design goals for
ultimate endurance in the battery only mode. Unless you're
willing to settle for a relatively SHORT endurance mode like
30 minutes (I hope most of my OBAM aircraft builders are
planning for duration that equals or exceeds that of fuel
aboard), then your battery(ies) will be replaced LONG before
they quit cranking the engines and long before they would
have been subject to the wear and tear that promotes shorted
cells.
>. It will also allow us to run power with the engine not running and then
>to isolate the depleted battery during start so it will not drag down the
>other one. We will be able to deplete it completely and still have enough
>juice for three starts with no charging required.
Dead batteries do not materially "drag a charged battery
down". It takes a bus voltage substantially in excess of
the battery's open circuit terminal voltage to put a charge
into the dead battery. A battery delivers energy at 12.5 volts
and DOWN. A battery needs to see 13.5 volts and HIGHER to
accept meaningful amounts of energy. If you connect a fully
charged battery to a dead battery, there will be a substantial
but very short lived current flow from the charged battery
into the dead battery. But the ENERGY transferred in this
event is a small percentage of the charged battery's total
capacity. Given that a typical engine cranking scenario
taps less than 10% of a battery's total capacity, the concerns
for loading effects of a dead battery in the system are
not supported by the physics.
It's not clear from our discussion thus far how just ONE of
TWO batteries becomes depleted. It seems that this happens
only because of inadvertent positioning of switches when
parking the airplane. If ONE battery can be run down by not
positioning all switches in accordance with the shutdown
checklist, then it seems that TWO batteries are at equal
risk.
It is my suggestion that if one plans to add a second battery
to a light twin, then it would be wise to go all the way
and craft a FULLY redundant architecture offered by
independent systems as shown in Z-14.
Sticking another battery onto the certified, stock single
engine electrical system with two alternators does not
take advantage of all the features a twin engine system
could have. Even our big biz jets drive a single battery
with two generators . . . the word "twin" has been mistaken
to imply "redundancy". I'll suggest that current certified
designs fall far short of what COULD be achieved by the
simple implementation of a Z-14 style architecture.
In the mean time, your concerns about battery depletion,
and battery shorts are not well supported by facts in
evidence or by the state of current technologies. In the
case of P-barons (or similar light twins) inadvertent
switch positioning is easily offset by judicious use
of checklists propped up with ACTIVE notification of low
voltage (flashing light on panel that says battery is ON
but alternators are OFF). Once you've taken care of the
battery depletion problem, then service life of the battery
is a simple matter of a well considered preventative
maintenance program that will pull a flooded battery from service
long before it will suffer intra-cell shorts. Better yet
put a VSLA battery in and the shorted cells issue goes
away completely.
>Maybe there will be no need to switch the ESSENTIALS BUSS to the second
>battery at all.
>
>(would you be kind enough to show me how can I find a Figure Z-30 or Z-12?)
Sure, you can find the z-figures along with a host useful materials
at:
http://aeroelectric.com/articles.html
The Z-figures are contained in the assortment of power distribution
diagrams published as an update to the AeroElectric Connection.
Folks who have revision 10 books can get the latest updates which
includes Appendix Z at:
http://aeroelectric.com/articles/Rev11/AppZ_R11C.pdf
Bob . . .
Message 2
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| Subject: | Re: 24V Starter & 12V System |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
At 12:17 PM 7/9/2005 -0500, you wrote:
>--> AeroElectric-List message posted by: "Mark & Lisa" <marknlisa@hometel.com>
>
>Bob (&/or other expert),
>
>In your last msg on this subject you told us how you'd added a "Starter
>Fault" circuit (a set of resistors and LEDs) to your drawing as a means of
>ensuring all contactors are correctly configured prior to engaging the
>starter.
>
>http://www.aeroelectric.com/PPS/Engine/Starter/24V_Starter_14V_System.pdf
>
>
>Since you show several resistors installed in the circuit, I wondered if
>LEDs designed to run from 12V (they already have resistors installed) like
>these would work?
Not without some re-design . . . and even then the performance
degrdes.
>http://rocky.digikey.com/WebLib/Chicago%20Miniature/Web%20Data/5110F%20Serie
>s.pdf
>
>If not, would you please provide specs on the proper LEDs?
ANY red led NOT fitted with a resistor. The circuit's operating
parameters are predicated on the 1.7v average operating voltage
of the "barefoot" LED.
>Would you please provide a little more depth on your "Starter Fault"
>circuit? I was able to follow the schematic for the rest of the system, but
>you lost me on this circuit. I can see how power gets back to the LEDs if
>K2, K3, K4 or K5 are stuck, but I don't understand what happens in the
>"Starter Fault" circuit itself. It seems that power can go either direction
>thru there, but that's as far as I get.
When you place the switch in the START position and before you
push the button, you want to know that ALL relays are OPEN. We
do this by placing a 1/2 of battery bias voltage on a junction
common to all four relays. The 1/2 battery voltage bias comes
from the divider R1/R2. If no relays are closed, then putting a
voltmeter on any part of the monitored circuitry would show
about 6v. If any one of the relays is closed, current through
the relay will either pull the 6V bias toward ground or toward
battery voltage. This causes a 'fault detection' current to flow
into or out of the voltage divider which causes one of the LEDs
to illuminate.
If there are no relays closed, the LEDs are dark and you know
that it's okay to press the button. An LED will light while
you're cranking but should go out when your finished showing
that the system is ready to switch to the parallel battery
NORMAL mode.
>BTW, you labeled both 150ohm 1w resistors connected to post 1 of S1 as "R1".
Rev E has been uploaded to:
http://www.aeroelectric.com/PPS/Engine/Starter/24V_Starter_14V_System.pdf
Bob . . .
Message 3
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| Subject: | Re: alternator testing |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
At 03:26 PM 7/9/2005 +1000, you wrote:
>--> AeroElectric-List message posted by: Doug Gray <dgra1233@bigpond.net.au>
>
>Bob,
>
>Re: http://www.aeroelectric.com/articles/Alternators/Alternator_Test.pdf
>
>The paper suggests (to me anyway) that the alternator field plus regulator
>current load alone
>exceeds 2 Amps. I am a little surprised that this is so high and I had
>not factored it in to my
>load analysis.
You don't need to. An alternator is rated for USEFUL output which
already accounts for energy used to excite its own field.
>Is this a typical load, and if so for what sized alternator?
>
>How does this current vary with alternator load?
>
>Is the rating of an Alternator inclusive of this load? That is, does an
>alternater rating of say 30
>Amps mean the Alternator 'system' can suppply 30Amps or only 28Amps if we
>assume the regulator and
>field are drawing 2 Amps.
Check out chapter 3 and then see if you have any
questions.
Bob . . .
Message 4
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| Subject: | IC A23 external antenna adapter |
--> AeroElectric-List message posted by: Charlie Brame <chasb@satx.rr.com>
I used a length of RG-58 cable from Radio Shack and installed female BNC
connectors on both ends. The RG-58 is more flexible than RG-400 and
rolls up easily for storage. It connects my A23 to a panel mounted male
bulkhead BNC which is permanently connected to an external antenna using
RG-400 cable. Works great.
Charlie Brame
RV-6A N11CB
San Antonio
> Time: 11:14:50 AM PST US
> From: "F. ILMAIN"
> Subject: AeroElectric-List: IC A23 external antenna adapter
>
> --> AeroElectric-List message posted by: "F. ILMAIN"
>
> Anyone knows what cable is need to connect an Icom A23 handheld (BNC) to an
> external Antenna (BK external antenna adapter plug)
> Thanks
>
>
Message 5
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| Subject: | Re: 24V Starter & 12V System |
--> AeroElectric-List message posted by: Jim and Lucy <jpollard@ciaccess.com>
I have a European built combine harvester that has a
12-volt electrical system with a 24 volt starter.
The contactor setup on it
uses one big contactor assembly where all the insides
are locked together so it all has to switch when engaged.
No real chance of part of it not switching unless
the inside brakes somehow. There are fuseable link strips
across terminals under the wire access cover in case
somthing somewhere gets shorted.
It is made by bosche.
Yikes I just looked up the price and it is 500 dollars.
Ill hope it lasts a verylong time.
This probably wont help but there may be other switches
in big truck stores like this you could look at. Bobs
diagram looks much easier to fix out in the field.
Jim Pollard
Merlin Ont.
Message 6
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| Subject: | Z13 with B&C Alt/Reg combination ? |
--> AeroElectric-List message posted by: "Bill Schlatterer" <billschlatterer@sbcglobal.net>
Bob, am I missing something? I was looking for the Z13 diagram with the B&C
alt/reg combination and can't seem to find it. Would be great to see with
P-mag but assume you can just add in the R11C Z13 w/P-Mags.
Bill S
RV7a Arkansas
>
>(would you be kind enough to show me how can I find a Figure Z-30 or Z-12?)
Sure, you can find the z-figures along with a host useful materials
at:
http://aeroelectric.com/articles.html
The Z-figures are contained in the assortment of power distribution
diagrams published as an update to the AeroElectric Connection.
Folks who have revision 10 books can get the latest updates which
includes Appendix Z at:
http://aeroelectric.com/articles/Rev11/AppZ_R11C.pdf
Bob . . .
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