Today's Message Index:
----------------------
1. 12:52 AM - Re: Alternator with no battery? (D L Josephson)
2. 04:22 AM - Re: Re: Alternator with no battery? (C&K)
3. 04:42 AM - Re: Alternator with no battery? (donjohnston)
4. 06:04 AM - Re: Re: Alternator with no battery? (Robert L. Nuckolls, III)
5. 07:10 AM - Re: Alternator with no battery? (user9253)
6. 10:02 AM - Re: Re: Alternator with no battery? (Justin Jones)
7. 01:53 PM - Re: Alternator with no battery? (donjohnston)
8. 04:12 PM - Re: Lighted Toggle Switch recommendation (DeWitt Whittington)
Message 1
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Subject: | Re: Alternator with no battery? |
The OP asked not for analysis of the reported automotive failure, but
> Does anyone know what the impact of a loss of battery output (wire coming loose,
> solenoid failing, battery falling out of the plane, being stolen in flight by
> aliens, etc.) on the output of the alternator (with engine running at cruise
> power)?
> It would seem to me that if the load is less than the output of the alternator,
> it should continue to put out power as long as the engine is running.
In most cases it would, but there are other problems due to the high ripple component
of some alternators Rotax for instance recommends a 22,000 uF capacitor
specifically to smooth the ripple from their PM alternator in case the battery
is not functioning. Homebuilders using low impedance capacitors with heavy screw
terminals are on the right track. Some LSA manufacturers use tiny caps with
thin wires, not a good recipe if you really want to get pulses of current at
the full alternator rating into and out of the capacitor.
Message 2
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Subject: | Re: Alternator with no battery? |
An open battery contactor with an external regulator that is sensing
voltage at the battery is going to go high voltage and be expensive.
Different situation wih the sense wire on the alternator side of the
contactor or an internal regulator. No guarantees but I have seen those
continue to function fine when a flooded cell battery went open circuit.
Ken
Message 3
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Subject: | Re: Alternator with no battery? |
dlj04(at)josephson.com wrote:
> The OP asked not for analysis of the reported automotive failure, but
>
>
> > Does anyone know what the impact of a loss of battery output
>
A thousand "thank you's" kind sir! :D
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=443067#443067
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Subject: | Re: Alternator with no battery? |
Anecdoteally...
BobN has suggested that some aircraft (I think he mentioned a Bonanza
or Baron) can operate in an alternator-only,
no-battery-in-the-circuit mode, but I don't have any knowledge of
this. Perhaps the aircraft in question has a very exotic
regulator. BobN can speak to this better than I.
Actually, I designed several regulators
for Beech wherein the a requirement in the
RFQ was that the regulator, when paired with
the Bonanza and Baron alternators of the time,
would come alive self-excited . . . and run
self excited with no battery on line.
This was my first, second and third
regulator designs . . . had no idea if
anything 'special' was needed. As it
turn out, nothing really special. What
was NOT spec'd was the recovery profile
from a large load change . . . especially
a load dump. The overshoot would trip
the ov protection . . . but the transient
was still inside DO-160 qualification
levels.
What I discovered then was that the alternator
output was stable but subject to pretty
big, transient swings of voltage for large
changes in load. Like turning a 100+
watt landing light on/off . . . or perhaps
cycling an electrically driven, landing
gear pump.
Loss of battery in a stable load configuration
would probably go unnoticed and represent
no threat to system hardware. If the hardware
is DO-160 qualified, then transients of 20 volts
for one second and 40 volts for 100 milliseconds
are tolerated. It's the no-battery scenario
that drove selection of the test requirements
spelled out in DO-160. See
http://tinyurl.com/ybhvxal
I'll do some playing with no-battery
systems then next time I get on the bench.
I have had auto mechanics tell me that if you disconnect the battery
while the engine is running - DON'T DO THAT! But if you do, it will
void the warranty on the electronic components of the vehicle.
Yeah . . . the same physics applies here.
In AUTOMOTIVE parlance, a "load dump" is
battery disconnect while alternator is under
heavy load . . . and the BATTERY is a substantial
part of that load. i.e. the battery is badly
discharged and the alternator is working hard
to replace stored energy. This generates the
same scenario as operating an airplane, alternator
only and turning off some heavy load.
Don't know about that 'void the warranty' thingy,
not sure how anyone would KNOW that it was a
deliberate disconnection. No doubt, some
dealerships are inclined to behaviors not
unlike some avionics techs of days gone by:
"Gee, I think a spike got it".
Most OEM equipment in cars is designed with
goals equal to or greater than DO160. I've
seen some specs for things like heated seat
controllers. An OEM brought one out to the BEECH
EMC building for testing services. The requirements
document from GM was about 1/2" thick!
You will notice that the old red Cessna master/alternator rocker
switch does exactly the same thing. It allows the pilot to turn the
alternator field on and off independent of the battery master but
when you turn-off the master it turns-off the alternator field thru
the mechanical interlock built into the switch.
I was at Cessna when the split-rocker master switch
was birthed. The functionality of the split-rocker
master has been emulated in most of the Z-figures
http://tinyurl.com/kdqwahq
This was a time when not all appliances were
vetted to DO-160 input voltage conditions . . .
and the alternators could not be counted on
to self-excite. Airplanes we delivered the
year before with generators would start up and
run very happily generator only. To this day,
so will Beechjets and Hawkers. This was very
EARLY in the switch from generators to alternators in
aircraft and we were certainly not designers
of engine drive power sources. So the split
rocker was a hedge against having to re-educate
pilots who knew less than we did!
Now to your question - What happens if the battery somehow gets
disconnected in flight due to master contactor failure, wire failure,
aliens, etc?
I see two possibilities:
1. The regulator keeps on regulating and buss voltage remains stable.
True 99% of the time
2. The reguator can no longer keep the voltage stable and buss
voltage goes up. If you have over-voltage protection, it trips and
keeps your avionics from being fried but leaves you without power.
(unless you have some kind of backup power source)
No
How your particular system will respond is anybody's guess. If you
have over-voltage protection, you could test it with little risk to
your avionics??? (preferable on the ground ;)
It's not a guess. The physics is well known.
There was discussion a while back here on the List about testing some
of these hypotheses, but that would take some hefty test fixtures and
some effort. I would like to play on that team if anyone is
interested in a team effort.
I've got some work to do at B&C this year and
I'm going to rebuilt their alternator test stand
with modern instrumentation and loads. I'll be
working on some products that will be tested for
these conditions.
I don't think we're going to learn anything new
but we can probably put some sense of scale and
order on the anecdotal tales based on a few
nuggets of physical fact and too little data
on circumstance . . . like that 'shorted battery'
thing in the NTSB report. I can assure you that
far too little is known about what brought that
airplane down. I have no foundation to argue about
the shorted battery . . . but I'm exceedingly
skeptical that battery failure was root cause
or even a major contributor. This was an automotive
conversion engine and the fact that the builder
had two batteries wired in parallel in the first
place raises some questions as to design goals
and understanding of the physics. A short in
one of two paralleled batteries would cause so
anomalous system readings but it doesn't bring
down the bus. Something else was going on.
Bob . . .
Message 5
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Subject: | Re: Alternator with no battery? |
> A short in one of two paralleled batteries would cause so anomalous system readings
> but it doesn't bring down the bus. Something else was going on.
Bob, this is very interesting. Can you explain the physics that apply when two
batteries are connected in parallel and one of them shorts internally? I had
always assumed that a low voltage on one battery would drag down the voltage
of a parallel battery. Pilots who fly aircraft with two batteries need to know
what symptoms will be and what action to take, if any.
Thanks, Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=443077#443077
Message 6
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Subject: | Re: Alternator with no battery? |
Sounds like another good case for an OVM.
> On Jun 5, 2015, at 05:02, Robert L. Nuckolls, III <nuckolls.bob@aeroelectr
ic.com> wrote:
>
> Anecdoteally...
>
> BobN has suggested that some aircraft (I think he mentioned a Bonanza or B
aron) can operate in an alternator-only, no-battery-in-the-circuit mode, but
I don't have any knowledge of this. Perhaps the aircraft in question has a
very exotic regulator. BobN can speak to this better than I.
>
> Actually, I designed several regulators
> for Beech wherein the a requirement in the
> RFQ was that the regulator, when paired with
> the Bonanza and Baron alternators of the time,
> would come alive self-excited . . . and run
> self excited with no battery on line.
>
> This was my first, second and third
> regulator designs . . . had no idea if
> anything 'special' was needed. As it
> turn out, nothing really special. What
> was NOT spec'd was the recovery profile
> from a large load change . . . especially
> a load dump. The overshoot would trip
> the ov protection . . . but the transient
> was still inside DO-160 qualification
> levels.
>
> What I discovered then was that the alternator
> output was stable but subject to pretty
> big, transient swings of voltage for large
> changes in load. Like turning a 100+
> watt landing light on/off . . . or perhaps
> cycling an electrically driven, landing
> gear pump.
>
> Loss of battery in a stable load configuration
> would probably go unnoticed and represent
> no threat to system hardware. If the hardware
> is DO-160 qualified, then transients of 20 volts
> for one second and 40 volts for 100 milliseconds
> are tolerated. It's the no-battery scenario
> that drove selection of the test requirements
> spelled out in DO-160. See
>
> http://tinyurl.com/ybhvxal
>
>
> I'll do some playing with no-battery
> systems then next time I get on the bench.
>
>
>
> I have had auto mechanics tell me that if you disconnect the battery while
the engine is running - DON'T DO THAT! But if you do, it will void the war
ranty on the electronic components of the vehicle.
>
> Yeah . . . the same physics applies here.
> In AUTOMOTIVE parlance, a "load dump" is
> battery disconnect while alternator is under
> heavy load . . . and the BATTERY is a substantial
> part of that load. i.e. the battery is badly
> discharged and the alternator is working hard
> to replace stored energy. This generates the
> same scenario as operating an airplane, alternator
> only and turning off some heavy load.
>
> Don't know about that 'void the warranty' thingy,
> not sure how anyone would KNOW that it was a
> deliberate disconnection. No doubt, some
> dealerships are inclined to behaviors not
> unlike some avionics techs of days gone by:
> "Gee, I think a spike got it".
>
> Most OEM equipment in cars is designed with
> goals equal to or greater than DO160. I've
> seen some specs for things like heated seat
> controllers. An OEM brought one out to the BEECH
> EMC building for testing services. The requirements
> document from GM was about 1/2" thick!
>
>
> You will notice that the old red Cessna master/alternator rocker switch do
es exactly the same thing. It allows the pilot to turn the alternator field
on and off independent of the battery master but when you turn-off the mast
er it turns-off the alternator field thru the mechanical interlock built int
o the switch.
>
> I was at Cessna when the split-rocker master switch
> was birthed. The functionality of the split-rocker
> master has been emulated in most of the Z-figures
>
> http://tinyurl.com/kdqwahq
>
> This was a time when not all appliances were
> vetted to DO-160 input voltage conditions . . .
> and the alternators could not be counted on
> to self-excite. Airplanes we delivered the
> year before with generators would start up and
> run very happily generator only. To this day,
> so will Beechjets and Hawkers. This was very
> EARLY in the switch from generators to alternators in
> aircraft and we were certainly not designers
> of engine drive power sources. So the split
> rocker was a hedge against having to re-educate
> pilots who knew less than we did!
>
>
>
> Now to your question - What happens if the battery somehow gets disconnect
ed in flight due to master contactor failure, wire failure, aliens, etc?
>
> I see two possibilities:
> 1. The regulator keeps on regulating and buss voltage remains stable.
>
> True 99% of the time
>
>
> 2. The reguator can no longer keep the voltage stable and buss voltage goe
s up. If you have over-voltage protection, it trips and keeps your avionics
from being fried but leaves you without power. (unless you have some kind o
f backup power source)
>
> No
>
>
> How your particular system will respond is anybody's guess. If you have o
ver-voltage protection, you could test it with little risk to your avionics?
?? (preferable on the ground ;)
>
>
> It's not a guess. The physics is well known.
>
>
> There was discussion a while back here on the List about testing some of t
hese hypotheses, but that would take some hefty test fixtures and some effor
t. I would like to play on that team if anyone is interested in a team effo
rt.
>
> I've got some work to do at B&C this year and
> I'm going to rebuilt their alternator test stand
> with modern instrumentation and loads. I'll be
> working on some products that will be tested for
> these conditions.
>
> I don't think we're going to learn anything new
> but we can probably put some sense of scale and
> order on the anecdotal tales based on a few
> nuggets of physical fact and too little data
> on circumstance . . . like that 'shorted battery'
> thing in the NTSB report. I can assure you that
> far too little is known about what brought that
> airplane down. I have no foundation to argue about
> the shorted battery . . . but I'm exceedingly
> skeptical that battery failure was root cause
> or even a major contributor. This was an automotive
> conversion engine and the fact that the builder
> had two batteries wired in parallel in the first
> place raises some questions as to design goals
> and understanding of the physics. A short in
> one of two paralleled batteries would cause so
> anomalous system readings but it doesn't bring
> down the bus. Something else was going on.
>
>
> Bob . . .
>
>
>
==========================
=========
==========================
=========
==========================
=========
==========================
=========
>
Message 7
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Subject: | Re: Alternator with no battery? |
This is very interesting. Thanks to everyone for participating.
So is it safe to say that the battery is providing a type of surge suppression
(or power leveling or fluctuation dampening) function in this circuit?
And if it's correct that the absence of the battery could cause an over voltage
situation, is there a way to mitigate that? Or is that scenario so unlikely that
it's not worth protecting against?
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=443107#443107
Message 8
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Subject: | Re: Lighted Toggle Switch recommendation |
I'm still trying to find the exact part number, Hari, for our Honeywell,
lighted rocker switches for our Sportsman. We bought them through John
Stark in Columbus, Georgia, who built our panel. I'll see if Doug Hanson,
my partner who is the electrical guru knows.
Dee
DeWitt (Dee) Whittington
Richmond, VA
804-677-4849 iPhone
804-358-4333 Home
On Thu, Jun 4, 2015 at 12:03 PM, Hariharan Gopalan <rdu.hari@gmail.com>
wrote:
> Hello Group
>
> Is anyone using lighted toggle switches? Looking for recommendations.
>
> Thanks
> Hari
>
> *
>
>
> *
>
>
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