Today's Message Index:
----------------------
1. 01:05 AM - Re: duracell battery leak (jerb)
2. 07:01 AM - Re: Re: Ammeter help (Robert L. Nuckolls, III)
3. 07:09 AM - Re: In-line Battery Fuse; great find (Robert L. Nuckolls, III)
4. 09:50 AM - Re: Ammeter help (user9253)
5. 04:59 PM - Re: Re: Ammeter Help (John Burnaby)
6. 06:57 PM - Re: Contactor Failure (speedy11@aol.com)
7. 07:50 PM - Re: Re: Re: Ammeter Help (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: duracell battery leak |
Question, can any one correlate the time frame when the Duracell's
began leaking more frequently. Since Gillette acquired them, Proctor
and Gamble has since acquired Gillette. One other thing, is there
any correlation to their leaking since product had been released the
Duracell as Ultra product and CopperTop. Sure would like to see them
get a handle on the problem and make them like they used to - you
could trust them not to leak in ones expensive toys like test
equipment, cameras, etc. By the way according to their customer
service department I was told if you should have one of their
alkaline batteries leak, use vinegar to clean to the terminals and
battery compartment area as alkaline is a base and is neutralized by
the acid in the vinegar.
jerb
At 03:20 PM 12/21/2009, you wrote:
>
>Listers,
>
> Just another data point. I had a Duracell AA battery sitting in a
>battery holder on a shelf and I just looked at and the bottom had leaked
>while it was sitting in the holder. This has been stored at room temp
>and was slightly used but showed good on the little built in tester when
>I put it in the holder.
>
>Raymond Julian
>
>
Message 2
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| Subject: | Re: Ammeter help |
At 01:21 AM 12/22/2009, you wrote:
Folks;
Thanks to all who replied-all of it useful.
However, I need an explanation, most likely from Bob regarding ammeters.
Bob, I recently purchased rev 12 of the
Connection. Page 4-9, last paragraph says: A
zero center, battery ammeter is the most
desirable and should be the first electrical system instrument you install.
Again, on page 7-12, last paragraph, you state:
if you plan only one electrical system
instrument, make it a battery ammeter..
With the above being in your book and presumably
vetted by yourself, I became confused when I read
in your response to my original post, the
following: Battery ammeters are of limited
utility and again the ammeter offers no
useful data for operating the airplane
I need to ask did I completely misinterpret the
book? I have Rev 12, which I am led to believe is
the most current (no pun intended), or has your
mind changed substantially since 12 was
published? If that is the case, would you be
willing to expound and elucidate on the subject
of the necessity of ammeters in the cockpit? Thanks in advance.
Keith
PS The book is great. I did not become aware of
it until I attended an EAA SportAir class where it was highly recommended.
Aha! You read the book! I'm pleased that you've
not only noted this 'disconnect' but that you brought
it to the attention of the List . . . Oh yes, thank
you for the kind words. I'm pleased that you found the
work useful.
The chapter on instrumentation is one of the oldest
in the book . . . and is seriously in need of updating.
An explanation of what I've written (both times)
is in order.
Many, many moons ago, folks who where bolting the
first generators, batteries and rudimentary mobile
electro-whizzies to cars. They no doubt pondered the
best way to tell the operator of the automobile that
things were going well in the production, storage
and utilization of electrical energy.
If you had an opportunity to fill one hole on
the instrument panel with a electrical system
monitoring instrument in 1915, what would your
choice be? A voltmeter would be cool. 7 volts
or more with the engine running and all electro-
whizzies turned on would be a comforting thing
to know. But you could still have a soggy
battery. Hmmmm . . . well, we DO load test the
battery every time the car is started . . . but
then, there's not much advance warning of battery
aging . . .
Alternatives to voltmeters were ammeters . . .
simpler, much more rugged than voltmeters, but
where to install it? As it turns out, placing
a -0+ ammeter in series with the battery charge/
discharge line showed promise. If the ammeter
reads zero, then the battery is 'happy' (or
everything is turned off!). By 'happy' we mean that
bus voltage is high enough to keep the battery
from being discharged . . . and the battery has
taken on all the charge it can . . . AT THAT
PARTICULAR bus voltage. Hmmm . . . assuming that
the regulator's set-point is where it belongs
then the battery-ammeter's interpretation is
simple and accurate.
Now, you not only have a means by which day-to-
day wellness of the system can be watched,
you can compare today's ammeter actions after
engine-start with those you observed a month
ago . . . oh yeah, you DO take note of such
things while conducting a 3-page check-list,
right?
The battery ammeter was a useful and probably
the most practical thing you could do for a
machine that never leaves the ground.
But I'd bet not one driving citizen in 1000
understood and could accurately interpret what
the ammeter was telling them. I recall an
episode in my teenaged years where my favorite
mechanic was talking with a customer who just
drove up to complain that his battery "wasn't
charging". He had tried many times to explain
to the man that the battery would 'charge' only
when it needed to . . . and all other times
the ammeter should and would read zero.
So, in the context of my life-experiences
up to the time I wrote that chapter, yeah,
the battery ammeter was a pretty informative
device. Indeed, virtually all single engine
Cessna's sported this as the only electrical
system instrument for decades. In fact,
those-who-know-more-about-airplanes-than-we-do
have decreed:
FAR 23.1351(d) Instruments. A means must exist to indicate to
appropriate flight crewmembers the electric power system
quantities essential for safe operation.
(1) For normal, utility, and acrobatic category airplanes with direct
current systems, an ammeter that can be switched into each generator feeder
may be used and, if only one generator exists, the ammeter may be in the
battery feeder.
(2) For commuter category airplanes, the essential electric power system
quantities include the voltage and current supplied by each generator.
Charles Kettering would probably be pleased that
his ideas from 1912 were adopted as policy by an
agency of government. Problem is that while battery
ammeters are capable of displaying some important
information about electrical system function, they
have serious drawbacks. (1) the folks looking
at the instrument need to understand what the readings
mean based on some 'empathy' with how various components in
the system are behaving and (2) they're not easily
implemented in the Z-figures using SHUNTS because
we'd like NOT to bring alternator b-leads into the
cockpit if we can avoid it. Furhter, we don't want
to run starter current through a shunt that is
trying to resolve readings down 1 or 2 amps on
a 2" instrument.
20 years later . . .
In our collective deliberations as designers,
fabricators, operators and maintainers of our
own airplanes we've adopted policy and practice
that MONITORS battery condition for the purpose of
meeting design goals for a lot more than 30 minutes
of battery-only endurance. It's unlikely that
even the most attentive pilot is able to resolve
a 20% drop in battery capacity by observing the
behaviors of a battery ammeter.
Further, accurate voltmeters are much easier
to come by compared to Uncle Charles' time. Shucks,
about everyone with a digital display throws a
voltmeter in just for grins. Regulator set-points
have become much more stable too. So as it turns
out now, the single most valuable electrical system
instrumentation today is a simple low voltage warning
light that says "Hey Zeek! . . . you're in battery-only
ops. Time to go to plan-B!".
Assuming your plan-B is well crafted and MAINTAINED,
you may confidently continue flight to airport of
intended destination without breaking a sweat.
This confidence comes with a price of admission.
You need to understand how all those things in your
airplane's electrical system work. What demands they
have for electrical power and what utility they
offer or comfortable termination of flight. You
then take it upon yourself to make sure those demands
are satisfied if and when the alternator quits. Even
with Z-13/8, you have greater ability or power electro-
whizzies if the big dog goes to sleep . . . but it
is STILL LIMITED.
The short answer is: The battery ammeter as a single
display of electrical system functionality can be and
has been quite useful for nearly 100 years. I
suggest that present day goals and expectations
for system performance would raise the eyebrows if
not elicit guffaws from our brethren who thought
their 1965 C-182 was the greatest thing on wings.
So without trashing what generators, flooded batteries,
venturi powered t/b, and yes . . . battery ammeters
offered us in the past . . . I'll suggest it's time to set
them aside in favor of more efficient and certainly more
capable recipes for success.
If your chunk of panel-glass comes with a hall-effect
sensor, you can certainly count the flow of electrons
in any wire you wish . . . including a battery cable.
No matter where you decide to install it, know that
the readings it offers are useful only if the observer
understands WHY they say what they do. The same observer
must be capable of sorting through the permutations that
resolve a sense of electrical system health. I.e.,
the ammeter is first a DIAGNOSTIC tool and a second a
poor warning tool. That little flashing LV WARNING
light is the elegant tool for flight operations.
Revision 13 to the book will have a whole new chapter
on monitoring the health of the electrical system.
Bob . . .
Message 3
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| Subject: | In-line Battery Fuse; great find |
At 01:35 AM 12/22/2009, you wrote:
>Good point- I have a problem with the aircraft architecture though;
>the kit manufacturers don't tell you where you can drill holes into
>structural members so I had to go around them and through different
>members. I didn't want to drill too many holes or stuff a lot of
>thinner wires into a small hole so I decided to run one fat wire
>that is well protected, both electrically and mechanically (much
>easier to do with one fat wire than many thin ones) up to the front.
>
>In this instance the battery bus is not a battery bus as defined,
>but I have been able to get a second battery in at the back of the
>aircraft without making too many holes in important places.
>
>Jay
Then as an auxiliary battery with all feeders capable
of delivering hazardous levels of energy in a crash,
then incorporation of a battery contactor at the battery
is indicated.
I think I mentioned some years back an anecdote offered
by a good friend and colleague at Beech. Before joining
the electrical design group he spent a number of years
digging around in smoking holes. He noted once
at lunch that every crash he investigated when the
airplane didn't burn, the ship's battery was most likely
found tossed out somewhere into the woods. If the airplane
burned, the battery was most likely located in the
wreckage.
If you're not planning on an system for ejecting the
battery(ies) when on short final to the rocks, then
having a short-coupled battery contactor and/or minimally
fused battery busses is the next best thing.
Bob . . .
Message 4
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| Subject: | Re: Ammeter help |
Keith,
The most important electrical instrument is the voltmeter. If the voltage is
above 14, then you know that the alternator is working and that the battery
is being charged. If the voltage is below 14 and is slowly dropping, then the
alternator is not working. Having a voltmeter or other low voltage warning is
essential. An ammeter is optional.
The location of the current shunt or sensor is a matter of personal preference.
The ammeter that you are considering, 30-0-30, measures current going into
or out of the battery. Current should usually only flow into the battery (above
zero indication) except when the engine is off or perhaps when short term
heavy loads are turned on, such as motors. The information provided by this
type of ammeter is not very useful because the voltmeter already tells if the
battery is being charged or not.
Another possible location for the current shunt is in the alternator B lead.
Current in the B lead only flows in one direction, so the meter would not have
a below-zero scale. Since the alternator normally supplies current to the aircraft
(not the battery), knowing this current is useful because you know that
the alternator is working; and you also know how much total current the aircraft
is using for charging the battery and operating the electrical equipment.
Once the battery is fully charged, not much current flows into it. Then the
ammeter indicates current being used by other electrical loads. If the alternator
fails, the ammeter will read zero and you will not know how much current
the aircraft is draining from the battery.
A third possible location for the ammeter shunt is in the wire supplying power
to the Main Power Distribution Bus. The meter would not have a below-zero
scale. In this location the ammeter will tell you exactly how much current is
being used by your electrical equipment. You could turn on one device at a time
to determine its current consumption. Wired like this, the ammeter will not
tell you if the current is coming from the battery or from the alternator (but
the voltmeter will).
It is up to the builder to decide if an ammeter is useful and if so, then where
in the circuit to install it.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=278585#278585
Message 5
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| Subject: | Re: RE: Re: Ammeter Help |
Keith thanks for bringing this up.
I was going to install an ammeter in my bird until this subject arose
and and I really started thinking about what useful info the meter would
provide.
I'm building an all electric plane and thought it would be useful to
have an ammeter on board to aid in alternator-out conditions. I intend
to conduct battery capacity tests, at my full E-bus load, between
annuals so that, with an ammeter indicating load on the battery(s), I
would have a reasonable idea of my electrical endurance during alt-out.
My first inclination would be to land at the first opportunity. But I
might choose a more convenient airport further away if I knew my
battery(s) would last with a margin.
I suppose that a voltmeter might be more useful because I know at what
voltage critical components become inop. Electronic ignition will work
down to 7 volts, but at a cost in amps. Ditto electronic fuel injection
with an even heavier amp load to drive injectors. Haven't tested my fuel
pumps but I suspect the motor would be an amp hog as well at low volts.
So with the knowledge of battery ampacity from semi-annual tests and a
knowledge of my full E-bus load, I would have a ballpark of my
electrical endurance during alt-out and the rate at which the voltmeter
was dropping would be a cross check.
OK! I now think that a voltmeter is more useful for determining
electrical endurance than an ammeter that just tells me my burn rate,
which I already know from system architecture calcs. An ammeter is
similar to a fuel flow meter. Knowing how much fuel you're burning is
not particularly useful without knowing how much fuel you have. If you
can see your fuel level, you can change throttle settings accordingly.
Ditto on electricity.
John
Message 6
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| Subject: | Re: Contactor Failure |
Bob,
Sorry to be so long in responding.
Very interesting analysis.
I will follow your advice.
Thanks,
Stan Sutterfield
At 08:46 AM 12/2/2009, you wrote:
The continuous duty contactor I have installed is temporary. I will
replace it with an intermittent duty one.
I installed the Skytec starter as it arrived from the manufacturer -
that is, with the jumper from the contactor's control line to the
main terminal installed. I left the jumper installed because Skytec
recommend it - see
http://www.skytecair.com/images/Certified%20LS%20Wiring_1100.jpg. My
error, of course, was that I left out what they call the master solenoid.
I'm just guessing . . . but this configuration was probably
crafted to MINIMIZE changes to an existing system in a TC
aircraft. Adding the jumper to the starter contactor (a
technique adopted by B&C many years earlier) offers three
advantages. (1) you get a drop-in replacement of a previously
installed starter and (2) buffers existing ship's wiring from
experiencing the extra-ordinary inrush offered by the two-stage
solenoids as described in my article and (3) the PM motor inrush
current doesn't hit the system until BOTH the standard starter
and built-in contactors close. Since the standard contactor
closes first, there's a potential for improving life of this
contactor IF it's contacts are closed and stable when the
second set of contacts on the starter get closed a few milliseconds
later. The DOWNSIDE is the potential for suffering delayed
pinion dis-engagement.
This is Van's recommended wiring
http://www.skytecair.com/images/Van's%20Starter%20Wiring%20Lg.jpg,
but Skytec recommends against wiring this way.
This is pretty slick. The diagram suggests using the auxiliary
"I" (ignition boost) terminal available on most starter
contactors to close the starter-mounted contactor . . . again
with the idea of shifting motor inrush currents to the
starter's internal contactor. It has the advantage of breaking
the internal contactor's coil current when the external starter
contactor opens. This accomplishes the same goals as Z-22
but with an external STARTER CONTACTOR as opposed to an external
BUFFER RELAY.
Bob, are you implying that I should have removed the jumper wire from
the starter?
Not implying, recommending . . . based on what we learned
about (1) delayed disengagement and (2) higher stresses
on starter control contactor with substitution of PM
motor technology. If you already have an external contactor
installed (a la Van's suggestion) then making a simple change
to remove the jumper and wire the internal contactor control
terminal to the external contactor "I" terminal would be
a good move.
Van's drawing or Z-22 is the elegant solution for new design
in an OBAM aircraft. Skytec's drawing is the less than elegant
solution for minimizing changes to a TC aircraft when replacing
original starter called out on the ship's certification documents.
The way you had it wired ORIGINALLY wasn't all that hard on
the external contactor . . . assuming that it's contacts were
closed and stable before the internal contactor gets closed.
I've not had an opportunity to measure it but I suspect this
is the case. THEREFORE, I'm comfortable with suggesting that
your original sticking failure was probably an isolated case
and not indicative of a system design error. ADDING the battery
master contactor in series with cranking currents is the
firewall against a future repeat causing you to burn a battery
or starter.
Adding the wire to conform to Van's suggested configuration
would be a good move to take care of the potential for delayed
disengagement.
Bob . . .
Message 7
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| Subject: | Re: RE: Re: Ammeter Help |
At 06:50 PM 12/22/2009, you wrote:
>Keith thanks for bringing this up.
>
>I was going to install an ammeter in my bird until this subject
>arose and and I really started thinking about what useful info the
>meter would provide.
>
>I'm building an all electric plane and thought it would be useful to
>have an ammeter on board to aid in alternator-out conditions. I
>intend to conduct battery capacity tests, at my full E-bus load,
>between annuals so that, with an ammeter indicating load on the
>battery(s), I would have a reasonable idea of my electrical
>endurance during alt-out. My first inclination would be to land at
>the first opportunity. But I might choose a more convenient airport
>further away if I knew my battery(s) would last with a margin.
Which is the basis for crafting Plan-B. When the
LV warning light comes on, it seems more useful to
KNOW in advance what equipment items you plan to
run. It's equally useful to KNOW in advance that
the battery was recently determined to contain
the energy YOU have set down in design goals
for YOUR plan B . . . of course this would include
any margins that contribute to your confidence
levels.
>
>I suppose that a voltmeter might be more useful because I know at
>what voltage critical components become inop. Electronic ignition
>will work down to 7 volts, but at a cost in amps. Ditto electronic
>fuel injection with an even heavier amp load to drive injectors.
>Haven't tested my fuel pumps but I suspect the motor would be an amp
>hog as well at low volts.
If you have an electrically dependent engine then
perhaps your plans should include a second alternator
capable of supporting the engine . . .
>
>So with the knowledge of battery ampacity from semi-annual tests and
>a knowledge of my full E-bus load, I would have a ballpark of my
>electrical endurance during alt-out and the rate at which the
>voltmeter was dropping would be a cross check.
It's inarguable that a voltmeter COULD be used to
assist you in worrying about what ever energy remains
in the battery. I'll simply suggest this is something
akin having discovered that you may not have accurately
accounted for fuel necessary to make the leg . . .
whereupon cursing those lousy fuel gages becomes a
distraction to your piloting duties.
Watching the voltmeter with an alternator dead
is no less a distraction . . .
>
>OK! I now think that a voltmeter is more useful for determining
>electrical endurance than an ammeter that just tells me my burn
>rate, which I already know from system architecture calcs. An
>ammeter is similar to a fuel flow meter. Knowing how much fuel
>you're burning is not particularly useful without knowing how much
>fuel you have. If you can see your fuel level, you can change
>throttle settings accordingly. Ditto on electricity.
Well considered. May I further suggest that you
are best served by having a well crafted Plan-B
paired with a confidence that your well maintained
equipment will perform as designed?
So, when the light comes on, you need only
configure for plan-B ops and arrange to be on the
ground within parameters set by your well
considered and accurately achieved design goals.
Once on the ground, you'll discover that troubleshooting
the system requires voltmeters and/or ammeters
to supplement any such indicators that already
exist on the panel.
Bob . . .
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