Today's Message Index:
----------------------
1. 05:38 AM - the battery dragon . . . (Robert L. Nuckolls, III)
2. 08:25 AM - OFF DIY engine monitor (Joe & Jan Connell)
3. 11:31 AM - "GAMI" Lean Check, Was: DIY engine monitor (BobsV35B@aol.com)
4. 04:19 PM - Re: Rear Mounted Batteries - more questions (RV_10)
5. 08:10 PM - OT: looking for ride (David M.)
Message 1
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Subject: | the battery dragon . . . |
>Comments/Questions: I am building a Jabiru J430 and plan to include your
>crowbar overvoltage system and low voltage detector. I am planning on a
>dual battery where the second battery supports the main bus but not the
>starter motor. The plan is to put a power diode between the bus and the
>main battery. This means that that both batteries will charge from the
>regulator but the second battery will not contribute to starting and
>provide a sink to the bus to ensure voltage is maintained to the bus even
>during starting. The idea is for the second battery to keep the electics
>going in the event of main battery failure. Do you think this make sense?
Unless you're planning not to maintain your battery, then
'battery failure' is exceedingly remote. The battery can
be the most reliable source of power in the airplane.
Since you've expressed a concern for keeping certain
electro-whizzies operating under battery-only operations,
(1) WHICH devices are the most useful, how much (2) CURRENT
do they need and for (3) HOW LONG?
After you've deduced these answers, what is your (4) PLAN for
making sure that the battery in your airplane is up to the
task?
There are two qualifying tests of a battery. (5) LOAD testing
proves the battery's ability to carry high loads such
as starting the engine. This is the kind of test a service
station operator puts on your car battery using a device
similar to this one from Harbor Freight:
http://www.aeroelectric.com/Pictures/Tools/HF91129_4.jpg
Passing this test simply says the battery contains
sufficient ENERGY delivered through a sufficiently
LOW INTERNAL RESISTANCE to start the engine. The second
test is a measure of (6) CAPACITY. This proves the battery's
ability to perform under conditions (1), (2) and (3)
above.
It matters not how many batteries you install or how
you wire them if you do not craft a preventative
maintenance (a) PLAN to make sure your design goals for
battery only endurance are met. The fact that you
can get the engine started is but one of the two
features that need monitoring. Further, unless you
choose to meet an endurance load goal of a hand-full
of minutes (like the FAA's favorite 30), then you'll
need to establish some protocol for seeing that
your goals are met throughout your ownership of
the airplane.
This will involve either (b) periodic replacement
of what appears to be a perfectly good battery - cause
it started the engine or (c) periodic CAPACITY
TESTING against your personalized design goals
defined by (1), (2) and (3) above.
This can be easily accomplished with one battery
but it does commit you to deciding which protocol
offers the lowest cost of ownership. (b) throw a
new $50 battery in every annual or (c) acquire
the $tools$ and spend the $time$ to track your
battery's condition such that design goals for
battery only operations are consistently met.
What you've proposed in your query does not make
sense under the protocols established to operate
your airplane at all times confident that the
battery is going to be there to do the task you've
established for it.
The thing you need to do is establish PLAN (a) that
will embrace the philosophy of (b) or (c) and then
stick to it. If you do not have a copy of the
'Connection, I'll suggest you acquire or borrow one
and review chapter 17 on system reliability.
Join the AeroElectric-List and avail yourself of
the knowledge, experience and understanding of
dozens of folks who have slain the dragons you're
concerned with. It doesn't need to be expensive or heavy.
Bob . . .
Message 2
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Subject: | DIY engine monitor |
Guys,
Some of the postings on this topic have discussed the work
done by GAMI in regards to lean of peak. I might be incorrect
but the GAMI folks are usually working with fuel injection, not
carburetors. Please correct me if I'm wrong...
Joe Connell
Message 3
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Subject: | DIY engine monitor |
Good Afternoon Joe,
You are correct as far as why GAMI got involved in this endeavor.
It is also easiest to fix the balance if the engine is injected.
However, the diagnostic capabilities of the lean check are just as important
for a carbureted engine as they are for one that has fuel injection.
The problem is that it is much more difficult to correct poor distribution
on a carbureted engine.
There are many things that can be done, but I do not believe it is within
the realm of subjects appropriate to this list.
Do Not Archive
Happy Skies,
Old Bob
AKA
Bob Siegfried
Ancient Aviator
Stearman N3977A
Brookeridge Air Park LL22
Downers Grove, IL 60516
630 985-8503
In a message dated 3/31/2007 10:27:26 A.M. Central Daylight Time,
jconnell@rconnect.com writes:
Guys,
Some of the postings on this topic have discussed the work
done by GAMI in regards to lean of peak. I might be incorrect
but the GAMI folks are usually working with fuel injection, not
carburetors. Please correct me if I'm wrong...
Joe Connell
************************************** See what's free at http://www.aol.com.
Message 4
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Subject: | Rear Mounted Batteries - more questions |
Hello 'Lectric Bob,
Thank you for all the fantastic effort you put into this group. It is
extremely helpful to those of us with zero earlier experience in this area.
I have read the Connection a couple of times and I have been pondering the
whole issue of batteries and locations and fat wires etc.
Attached is a schematic of a Z-14, architecture for rear batteries. This is
not your current Z-14, and I don't know now where I got this from, but it
very specifically states that the Aft Ground Buss is NOT Grounded to the
airframe.
My wife and I are building an RV-10. We are planning an all electric IFR
panel and a two PC625 battery, two alternator electrical system. Would you
please make your comments specific to this setup?
Am I correct in assuming that there is an ideal setup for a two rear
battery, two alternator system, which is the Z-14 attached, and then there
is a more practical setup, which has the batteries grounded at the rear. Is
this correct?
Would you please comment on the relative merits of these two different
approaches, and especially comment on any downside of both approaches?
If you ground both rear batteries as suggested down the back to the
airframe, do you then set up your avionics ground bus at the panel simply by
connecting it to the firewall Ground? Are there any issues or concerns with
doing this?
>From a purely electrical perspective, would it be preferable in our
situation (ignoring weight and balance questions for the moment) to have
either battery situated up the front somewhere? If yes, which would be
preferable to put up the front, and why?
I also have a couple of other questions on the attached Figure Z-14. Does
the single ground lead from both batteries to the front provide a single
source of total failure? And lastly, why have you specified the copper/brass
strap on the power side of the main battery in the attached Z-14?
Thank you once again for all your very generous input.
John Cleary
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L.
Nuckolls, III
Sent: Thursday, 29 March 2007 12:28 AM
Subject: Re: AeroElectric-List: Rear Mounted Batteries - more questions
<nuckollsr@cox.net>
At 08:19 AM 3/28/2007 -0500, you wrote:
><lamphere@earthlink.net>
>
>Bob,
>
>Now you are confusing me..
>
>Yes, I did look at the link you provided.
>
>Using the generic aircraft - single battery schematic for schematic on
>metal tube frame.
>Battery (Odyssey 680) and contactor will be located under baggage
>compartment floor behind seat backs.
>
>I thought we were supposed to run a ground wire from the battery to the
>brass ground bus plate (with all the quick connect tabs on it) which was
>to be mounted on the firewall. Isn't using the airframe for ground now
>generating two paths for ground - hence possible problems?
Local grounds in all metal airplanes can practically
depart from "ideal" for the following:
Batteries, strobe supplies, landing/taxi lights,
pitot heaters, position lights, hydraulic pumps
for landing gear (because they're intermittent)
but not for air-conditioning compressors (because
they're continuous).
>I'm about ready to wire in my rear mounted battery (before covering). I
>will use flexible wire for the battery terminal connections (and to the
>local ground if that's what I am supposed to do). No problem attaching
>ground leads to the frame if a good idea. It would eliminate an extra wire
>to top and bottom strobes and tail position light... but I was already
>resolved to run + and gnd to each (using a small local-next to battery
>version of the brass ground bus with quick disconnects like in the front)
>
>I'd appreciate your input.
It's never 'bad' to run all electro-whizzies to a
single point ground but if one wishes to take advantage
of the ground-friendly, all-metal airplane with the
cited compromises, there's no risk of having an unhappy
noise moment.
It's most important to pay attention to grounding
potential victims such as avionics and instrumentation.
These should return to the firewall ground point per
Z-15.
I'll add some notes to Z-15 next revision to clarify
this point.
Bob . . .
Message 5
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Subject: | OT: looking for ride |
Will share fuel and flying for our leg, at least. My wife and I would like
to get from the Houston, Texas area to Huntsville, Alabama (preferably to
3M5, Moontown Airport) around April 17 or so. We have a car here in Houston
so we can drive a couple of hours to an airport, then we'll ride our bikes
back to Houston.
Thanks,
David M.
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