Today's Message Index:
----------------------
1. 07:58 AM - Re: Re: Load Monitoring (Robert L. Nuckolls, III)
2. 08:43 AM - Re: Alternator charging battery (Robert L. Nuckolls, III)
3. 09:28 AM - Firewall position of electrical components [RV-7A -- Z-13/8] (Lincoln Keill)
4. 10:20 AM - Time for a new PC 680 ? (thomas sargent)
5. 11:18 AM - Re: Time for a new PC 680 ? (Bill Mauledriver Watson)
6. 11:18 AM - Re: Firewall position of electrical components [RV-7A -- Z-13/8] (Greg Young)
7. 11:20 AM - Re: Time for a new PC 680 ? (Hinde, Frank George (Corvallis))
8. 11:21 AM - Re: Time for a new PC 680 ? (Byron Janzen)
Message 1
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| Subject: | Re: Load Monitoring |
At 12:53 PM 8/2/2009, you wrote:
>
>Bob,
>
>I really appreciate your insight into this stuff. I'm not just
>"kicking the tires" but really plane some installation in the near
>future and I'm just getting stuff lined up...
Understand.
>Regarding the PP regulators, I'm sure Les said that alternators of
>dissimilar outputs would load share based upon their respective max
>values...If, for example, you used the 20/60 amp combo and required
>40 amps, each alternator would be tasked with 50% of the load...but
>I'll check into it...I believe he said that it could be done by each
>regulator being fired up for the same amount of time...does that
>make sense to you?
sort of . . . but given my limited knowledge of
their design's inner workings, I'd be out of school
to offer well considered opinion.
>I'm not sure why that would work, but I'm pretty sure that's what he
>said was the basis for the idea. I believe both regulators are
>connected by a single wire that gives the feedback of them "knowing"
>how long to stay on.
This description suggests something of a synchronization
signal that causes the duty-cycle regulators to do some
sort of cooperative activity. But this is a kind of
"feed forward" or "open loop" control philosophy that
depends on or assumes certain things about the alternator
characteristics and operation.
The system may well have performed to design goals in
PP's testing and field experience with what ever
combinations of alternators were tried. My personal
experience suggests that the universal, "feed back" design
doesn't care about speeds, sizes or transfer functions.
It does the tight-wire balancing act by monitoring
actual alternator output as a proportion of total.
>Probably my final question on this topic: If more current is needed
>from an alternator than it is able to make, what happens?
Field voltage is max'd out. The regulator is turned on
hard. Now the alternator goes into a current limited
mode based on its physics and depending on how gross
the overload is, the bus voltage begins to sag.
>I expect that most of these alternators will produce more than the
>rated current. At PP they told me that the 60 amp will easily put
>out more than 70. I'm not advocating that anyone try it, and I
>expect there are a lot of bad things that would happen if one tried
>to do it for a long time. Excess heat and premature failure are two
>things I can think of, or even catastrophic failure of the
>unit...what I'm wondering is...what would occur if, say, the 60 amp
>unit failed and only the 20 amp unit stayed on line when the overall
>requirement was 50 amps.
You've touched on a small segment of the failure
modes considered for crafting your design. Paralleling
two alternators makes it difficult to tell when one
has failed unless the system is ALSO fitted with
gross imbalance detection and warning in addition to low
voltage warning. Making the two systems independent
of each other builds a solid partition between both
flight operations and failure detection.
If you had 50 amps being sucked from a 70A paralleled
system, the smaller alternator would go into current
limit and it's output sag until the battery picks up
the difference. I.e. bus voltage drops below 13.0 volts
and the battery joins the defence to keep the panel
lit up until (1) you become aware of the condition
and (2) react to it with a plan-b activity. But
nothing "smokes". In fact, a properly installed
alternator is essentially overload-proof. People
who have burned alternators up didn't "overload" them
with respect to their ratings . . . they "under-cooled"
them such that ratings could not be met without
over heating.
There's been much past discussion here on the List
about "de-rating" alternators to prevent bad-days
in the cockpit. The ratings are what the ratings are.
Continuous loading at or even past the nameplate ratings
without electrical damage . . . as long as you get the
heat out. We routinely TEST as-installed generators and
alternators to this design philosophy in TC aircraft.
>Would the 20 amp unit continue to do it's job to the best of it's
>ability, with the battery(s) picking up the slack for as long as
>they could, or would something worse happen?
>I'm wondering as this could be the situation IF the 60 amp unit
>failed and one continued with the 20. I expect I could get by
>indefinitely on the 20 as long it's pitot heat and/or lights were
>needed...just wondering if when that occurred, what would happen.
>
>I suspect that the alternator would do what it could and that the
>battery(s) would pick up the slack with the buss voltage going down
>from 13.8-14 to whatever voltage the batteries could
>supplement...like 12.2 something...
>
>What do you think?
Yup, you've figured it out. Your well maintained battery
steps in to hold the gremlins at bay until you can
react to the warnings.
>Sorry if this is an old question, but I'm new to the forum and
>didn't find anything with a search.
No problem sir. Out of 1800 other folks who frequent this
list, there's a bunch who haven't heard this before either.
This is a classroom, not a one-shot reference library.
Bob . . .
Message 2
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| Subject: | Alternator charging battery |
From: "Bob McCallum" <robert.mccallum2@sympatico.ca>
Subject: RE: AeroElectric-List: Alternator charging battery
Bob,
You've offered a great explanation of the physics of
battery charging as we understand it. I'll offer to
expand on your treatise as follows:
Charlie;
The wrong battery charger will eventually
overcharge and ruin any battery. Your 60 amp B&C
alternator puts out whatever current is required
(up to approximately 60 amps or so) to recharge
your battery and support system loads whether
right after starting or any other time its
turning quickly enough to do so. (Always assuming
everything is operating correctly of course) Yes
it has the ability to do that indefinitely. The
voltage regulator regulates the output of the
alternator to maintain the system voltage at the
required level, approximately 14 volts.
Exactly, battery charging behavior is very tightly
tied to system voltage. We know that the lead-acid
battery will EVENTUALLY assume 100% state of charge
if the system voltage is held at 13.8 volts. However,
a design goal for the use of batteries in vehicles is
to achieve a timely replacement of battery energy
used in pre-flight. The folks who have studied battery
physics in detail are in lockstep agreement. The
current "smart" chargers have a CONTROLLED recharge
protocol that looks like this:
http://www.aeroelectric.com/Pictures/Curves/Battery_Tender_Recharge.pdf
http://www.aeroelectric.com/Pictures/Curves/schumacher_3.jpg
If one wishes to MAXIMIZE battery life as a function
of charging protocols, then present thinking suggests
that you charge at best rate (what ever current your
charger is capable of) until the battery voltage
reaches a plateau in voltage that assures a timely
top-off for state of charge. This is generally on the
order of 14.5 volts.
Holding the battery at this charge level is mildly
abusive of the chemistry. In other words, once top-off
is achieved, holding the battery at this level whittles
away at the battery's chemistry in tiny chunks. It's
important to emphasize that this is only slightly
abusive of the battery. I had a GMC Safari with a
"bad" regulator that was ran 15.3 volts that didn't
kill the battery for the first two or three YEARS
that I owned the car. When I replaced the battery,
and discovered the too high voltage, I decided to
leave it and see how it goes.
The car ran another two years on the too-high voltage
before the alternator crapped . . . the new alternator
ran at 14.5 volts. But the battery did't get "cooked"
and was still in the car when I sold it a couple years
later.
However, the folks who have optimized battery CHARGING
and STORAGE protocols have told us that after top-off,
you can drop the system voltage to some value just
above the battery's open-circuit terminal voltage.
That number is just above 13.0 volts. Too low
to charge a battery, but high enough to keep the battery's
internal leakages from running the battery down
while stored.
If the battery is charged, then no more current
will flow into it and the alternator will just be
supplying system loads. Should the loads exceed
the alternators ability to supply current then
the battery will take up the slack. When system
loads are again reduced below the 60+ amps able
to be supplied by the alternator alone, then the
excess current will recharge the battery once
again until it is fully charged at which point
the alternator output will reduce to match the
system requirements. The only way to overcharge
the battery is for the regulator to fail and
cause the system voltage to rise too high.
Exactly. As I've described above, a system voltage
that is "too high" by perhaps a volt or more does
not stand your battery against the wall for execution.
It's not ideal but not automatically lethal.
Hence the desirability of over voltage
protection. The alternator only generates
whatever current is required not its full rated
output. Just like your battery might be capable
of supplying 1000 amps, but if all you have
connected is a single 6 watt light bulb, it will
only supply the amp or so required by that
light bulb, not the full 1000 amps its capable of.
This emphasizes the importance of PREDICTABLE and
reasonably ACCURATE control of the alternator (or
battery charger's output voltage). Plug-in-the-wall
battery chargers of yesteryear had NO voltage regulation.
They ranged from BOOST or CRANKING current levels
of a dozen to hundreds of amps of output capability.
These devices had to be SUPERVISED. You came back in
a few hours to disconnect the thing after you were
convinced that a top-off event had occurred. The
larger machines had a timer built in to prevent
inadvertent destruction of your battery if you forgot
to come back and shut the thing off.
Modern chargers offer some form of the battery
RECHARGE and MAINTENANCE protocols described
above and are suited for continuous and unlimited
connection to the battery being serviced. Your
alternator behaves in the same manner EXCEPT that
its regulator doesn't offer a set-back feature for
reduction of bus voltage after top-off. Given that
the duration of operation in the top-off mode is
tiny compared to the service life of the battery,
the cost of adding a "set back" feature in the
voltage regulator has a poor if not zero return
on investment.
Bob . . .
Message 3
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| Subject: | Firewall position of electrical components [RV-7A -- |
Z-13/8]
Did a search for this under the RV archive but couldn't find what I was loo
king for.- I just got my initial order from B&C of electrical system comp
onents (i.e. "electro-whizzies").- Can someone with an RV series aircraft
post or send me a picture/diagram/description of where on the firewall you
located the battery, starter contactor, battery contactor and B&C groundin
g block?- Van's firewall diagram doesn't really address this, although it
looks like he intends for the battery to be mounted down low on the right
side.- I'm planning on mounting an IO-320 (someday) and using a Z-13/8 ar
chitecture with a swing-down fuse block panel on the passengers side of the
sub-panel so this position would seem to make sense.- The contactors are
heavier than I expected so I'm guessing they need to be mounted on somethi
ng sturdier than just the firewall skin.- Any comments welcome.
Lincoln Keill
Sacramento, CA
RV-7A- fuselage
Message 4
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| Subject: | Time for a new PC 680 ? |
I have a PC-680 that I bought 2 or 3 years ago. I used it to test my
electrical system while I was wiring the plane. I've recharged it with a
motorcycle battery charger. It spent 99% of it's time doing nothing. Never
had much of a demand place on it. Still seems to hold a charge well. My
engine start is going to be in September, probably.
Should I replace this battery before I fly? It would seem prudent, though I
note they've gone up in price about 30% since I bought this one.
--
Tom Sargent
Message 5
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| Subject: | Re: Time for a new PC 680 ? |
I bought 2 PC680s a couple of years ago. Mainly did nothing but
notably, they were left in various stages of discharge for some period.
One just lost a cell. I'm still using both of them for avionics work
and keeping them charges but I will be swapping both out when I go
flying (next year?).
thomas sargent wrote:
> I have a PC-680 that I bought 2 or 3 years ago. I used it to test my
> electrical system while I was wiring the plane. I've recharged it
> with a motorcycle battery charger. It spent 99% of it's time doing
> nothing. Never had much of a demand place on it. Still seems to hold
> a charge well. My engine start is going to be in September, probably.
>
> Should I replace this battery before I fly? It would seem prudent,
> though I note they've gone up in price about 30% since I bought this one.
>
> --
> Tom Sargent
> *
>
>
> *
Message 6
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| Subject: | Firewall position of electrical components [RV-7A |
-- Z-13/8]
Are you planning the battery on the engine side of the firewall or inside?
IIRC the inside install has the contactors spec'd to be mounted on the
battery box and that's on one of the fuselage drawings. For the taildragger,
the Odyssey battery can be mounted on the right side with the contactors
just below it. The drawing has very specific locations for the battery box
and the contactors and a doubler so it ties to the firewall angles. The nose
wheel location is different due to the interference of the mount but I'm
sure it's equally as specific. It's on a drawing that comes with the
firewall forward kit. Firewall penetration points are on a different drawing
that may also be part of the FWF kit. If you didn't buy the FWF from Van's
then you probably don't have the right drawing. I borrowed them from a
friend but I think Van's will sell you any individual drawing for $3. Sorry
but I don't have the numbers handy.
Regards,
Greg Young
_____
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Lincoln
Keill
Sent: Monday, August 03, 2009 9:14 AM
Subject: AeroElectric-List: Firewall position of electrical components
[RV-7A -- Z-13/8]
Did a search for this under the RV archive but couldn't find what I was
looking for. I just got my initial order from B&C of electrical system
components (i.e. "electro-whizzies"). Can someone with an RV series
aircraft post or send me a picture/diagram/description of where on the
firewall you located the battery, starter contactor, battery contactor and
B&C grounding block? Van's firewall diagram doesn't really address this,
although it looks like he intends for the battery to be mounted down low on
the right side. I'm planning on mounting an IO-320 (someday) and using a
Z-13/8 architecture with a swing-down fuse block panel on the passengers
side of the sub-panel so this position would seem to make sense. The
contactors are heavier than I expected so I'm guessing they need to be
mounted on something sturdier than just the firewall skin. Any comments
welcome.
Lincoln Keill
Sacramento, CA
RV-7A fuselage
Message 7
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| Subject: | Time for a new PC 680 ? |
If you have kept it on a smart charger and you are electrically dependant..
then no do not replace it..It will be just fine.
If you have charged it occasionally but your running magnetoes and a mechac
nical fuel pump...then once again it will be fine.
If you Have electronic ignitions and electric fuel pumps (and have not kept
it regularly smart charged) , but it cranks over the engine then do all yo
ur phase one (day VFR) flying and consider replacing then....Before you do
long cross country flying where you might need the full capacity of the bat
tery to get you to a safe spot.
if it won't start the engine..well the choice is obvious.
Frank
________________________________
From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectr
ic-list-server@matronics.com] On Behalf Of thomas sargent
Sent: Monday, August 03, 2009 9:52 AM
Subject: AeroElectric-List: Time for a new PC 680 ?
I have a PC-680 that I bought 2 or 3 years ago. I used it to test my electr
ical system while I was wiring the plane. I've recharged it with a motorcy
cle battery charger. It spent 99% of it's time doing nothing. Never had m
uch of a demand place on it. Still seems to hold a charge well. My engine
start is going to be in September, probably.
Should I replace this battery before I fly? It would seem prudent, though
I note they've gone up in price about 30% since I bought this one.
--
Tom Sargent
Message 8
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| Subject: | Re: Time for a new PC 680 ? |
I would replace it, but if you have a magneto, you could probably get by. I
had one of these in my motorcycle for 6 years before it needed replacing.
IIRC, Mr. Nuckolls recommends changing every two years, but this may be for
dual electronic ignition aircraft.
On Mon, Aug 3, 2009 at 9:52 AM, thomas sargent <sarg314@gmail.com> wrote:
> I have a PC-680 that I bought 2 or 3 years ago. I used it to test my
> electrical system while I was wiring the plane. I've recharged it with a
> motorcycle battery charger. It spent 99% of it's time doing nothing. Never
> had much of a demand place on it. Still seems to hold a charge well. My
> engine start is going to be in September, probably.
>
> Should I replace this battery before I fly? It would seem prudent, though
> I note they've gone up in price about 30% since I bought this one.
>
> --
> Tom Sargent
>
> *
>
> *
>
>
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