Today's Message Index:
----------------------
1. 06:53 AM - The lithium saga slogs onward . . . (Robert L. Nuckolls, III)
2. 07:43 AM - Re: DIY CBOVM: variations on a theme (user9253)
3. 08:25 AM - Re: Re: DIY CBOVM: variations on a theme (Jeff Luckey)
4. 09:02 AM - Continental Motors magneto data (Robert L. Nuckolls, III)
5. 09:45 AM - Re: Re: DIY CBOVM: variations on a theme (K)
6. 09:54 AM - Re: DIY CBOVM: variations on a theme (user9253)
7. 09:55 AM - Re: Re: New Over-Voltage Protection Architecture (Robert L. Nuckolls, III)
8. 10:05 AM - Re: Re: DIY CBOVM: variations on a theme (Robert L. Nuckolls, III)
9. 10:26 AM - Re: DIY CBOVM: variations on a theme (user9253)
10. 10:59 AM - Re: Re: DIY CBOVM: variations on a theme (K)
11. 12:43 PM - The lithium saga slogs onward . . . (Robert L. Nuckolls, III)
12. 12:47 PM - Re: Re: DIY CBOVM: variations on a theme (Robert L. Nuckolls, III)
Message 1
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Subject: | The lithium saga slogs onward . . . |
In my quest to identify suppliers of lithium
batteries who will share operational details of
their BMS (battery management system) AND useful
contained energy plots, few suppliers have demonstrated
an interest in satisfying the unique curiosity of
those who build and fly airplanes.
So far, EarthX is the only one who has responded
positively. I have documentation that describes
their BMS operating philosophy. No family of
discharge curves yet . . . but them, most of their
customers are narrowly focused on engine cranking
cupcakes with a frosting of weight reduction.
I need to wrap of installment IV of the battery
series for Kitplanes . . . as of this moment, I'm
still short the necessary information to beat the
drums in favor of ANY commercial off the shelf
lithium product for OBAM aircraft.
My misgivings are NOT rooted in either disappointment
for weight savings or ability to get the engine started.
The problem is centered on knowing what we don't know . . .
exactly what size battery is needed to replace the
legacy SVLA products in which we have considerable
confidence.
Watch this space . . .
Bob . . .
Message 2
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Subject: | Re: DIY CBOVM: variations on a theme |
I repeated testing of the over-voltage circuit today, doing a better job of connecting
wires. If the voltage is steadily increased, the SCR fires at 16.2 volts.
But if the voltage is set at 16.0 volts and held there, the SCR would fire
after waiting a couple of minutes. Probing the input with a voltmeter intermittently
caused the SCR to fire only when the voltage was above 15.9. Circuit
instability, if any, is within 0.1 volt of the set-point. The adjustable voltage
power supply only cost $6. Who knows how stable that is. The components
are all through-hole, not surface mounted, and are mounted to a 1 x 2 inch
area of PCB. I am happy with the circuit.
I intend to connect the over-voltage circuit in series with a relay coil that
is powered by a 3 amp fuse.. The normally closed contacts of the relay will
be in series with the AC output of the permanent magnet dynamo. In case of high
voltage, the SCR will fire, connecting one leg of the coil to ground to energize
the relay, opening the AC circuit to the rectifier/voltage regulator. The
SCR will continue to hold the relay energized until battery power is disconnected
from the relay coil.
This will not be a crowbar type of over-voltage protection. So no circuit breaker
is required. High voltage will not blow the fuse.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=421067#421067
Message 3
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Subject: | Re: DIY CBOVM: variations on a theme |
Joe,=0A=0A1. How much power can the dynamo produce?- =0A2. Are there only
2 wires for the AC output? (I've never worked w/ a PM type alternator but
most non-PM machines have 3 wires for AC output)=0A3. As you probably alrea
dy know, on some relays, the current-handling capability of the NC contacts
is less than the NO contacts=0A=0A=0A-Jeff=0A=0A=0A=0A____________________
____________=0A From: user9253 <fransew@gmail.com>=0ATo: aeroelectric-list@
matronics.com =0ASent: Wednesday, March 26, 2014 7:40 AM=0ASubject: AeroEle
ctric-List: Re: DIY CBOVM: variations on a theme=0A =0A=0A--> AeroElectric-
List message posted by: "user9253" <fransew@gmail.com>=0A=0AI repeated test
ing of the over-voltage circuit today, doing a better job of connecting wir
es.- If the voltage is steadily increased, the SCR fires at 16.2 volts.
- But if the voltage is set at 16.0 volts and held there, the SCR would f
ire after waiting a couple of minutes.- Probing the input with a voltmete
r intermittently caused the SCR to fire only when the voltage was above 15.
9.- Circuit instability, if any, is within 0.1 volt of the set-point.-
The adjustable voltage power supply only cost $6.- Who knows how stable t
hat is.- The components are all through-hole, not surface mounted, and ar
e mounted to a 1 x 2 inch area of PCB.- I am happy with the circuit.=0A
- I intend to connect the over-voltage circuit in series with a relay coi
l that is powered by a 3 amp fuse..- The normally closed contacts of the
relay will be in series with the AC output of the permanent magnet dynamo.
- In case of high voltage, the SCR will fire, connecting one leg of the c
oil to ground to energize the relay, opening the AC circuit to the rectifie
r/voltage regulator.- The SCR will continue to hold the relay energized u
ntil battery power is disconnected from the relay coil.=0A- This will not
be a crowbar type of over-voltage protection.- So no circuit breaker is
required.- High voltage will not blow the fuse.=0AJoe=0A=0A--------=0AJoe
Gores=0A=0A=0A=0A=0ARead this topic online here:=0A=0Ahttp://forums.matron
==============
Message 4
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Subject: | Continental Motors magneto data |
Hat tip to Neal George who has provided
us with a helpful library of service and
training data on Continental's magneto systems.
List members are invited to review the documents
available at:
http://tinyurl.com/llpc5lj
. . . and download as their interest and needs
dictate.
Bob . . .
Message 5
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Subject: | Re: DIY CBOVM: variations on a theme |
In regards to stability you might check that there is a capacitor across
the voltage reference diode and another from the SCR gate to ground. If
you happen to have an old circuit diagram dated before about 2005 it may
not show that update.
One nice thing about the crowbar and circuit breaker in the Z diagrams
is that the voltage is brought under control immediately when the SCR
fires. If I understand your post it sounds like your implementation
waits for the relay to open and for any subsequent arcing to extinguish.
Perhaps that is good enough but it seems preferable to use the circuit
breaker as per the Z diagrams so that the SCR clamps the voltage faster.
Might be other small advantages as well such as a subsequent dead
battery could not cause the alternator to come back on line.
Ken
On 26/03/2014 10:40 AM, user9253 wrote:
> <fransew@gmail.com>
>
> I repeated testing of the over-voltage circuit today, doing a better
> job of connecting wires. If the voltage is steadily increased, the
> SCR fires at 16.2 volts. But if the voltage is set at 16.0 volts and
> held there, the SCR would fire after waiting a couple of minutes.
> Probing the input with a voltmeter intermittently caused the SCR to
> fire only when the voltage was above 15.9. Circuit instability, if
> any, is within 0.1 volt of the set-point. The adjustable voltage
> power supply only cost $6. Who knows how stable that is. The
> components are all through-hole, not surface mounted, and are mounted
> to a 1 x 2 inch area of PCB. I am happy with the circuit. I intend
> to connect the over-voltage circuit in series with a relay coil that
> is powered by a 3 amp fuse.. The normally closed contacts of the
> relay will be in series with the AC output of the permanent magnet
> dynamo. In case of high voltage, the SCR will fire, connecting one
> leg of the coil to ground to energize the relay, opening the AC
> circuit to the rectifier/voltage regulator. The SCR will continue to
> hold the relay energized until battery power is disconnected from the
> relay coil. This will not be a crowbar type of over-voltage
> protection. So no circuit breaker is required. High voltage will
> not blow the fuse. Joe
>
> -------- Joe Gores
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=421067#421067
>
>
Message 6
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Subject: | Re: DIY CBOVM: variations on a theme |
Jeff,
1. The Rotax 912 dynamo can generate up to about 20 amps. Although many recommend
not loading it to more than 16 amps. My plane uses about 10 amps.
2. Yes, the AC output has two wires and is single phase.
3. If I am interpreting this data sheet correctly http://pewa.panasonic.com/assets/pcsd/catalog/cb-catalog.pdf
the normally closed contacts can handle 30 amps. I suspect that, over the long
term, corrosion due to lack of exercise will be more of a problem than the contact
rating.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=421074#421074
Message 7
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Subject: | Re: New Over-Voltage Protection Architecture |
>Hmm, the link works for me.
>http://www.vansairforce.com/community/showthread.php?t=111102
>All 12 posting in this thread are from the last 2 or 3 days.
Yeah, had a momentary short between the heaphones.
Let's parse the narrative . . .
Last Wednesday I flew from Melbourne to Hobart in my RV-7 (about an
hour of the 2.5hr flight is over water - Bass Strait). Faultless day,
faultless flight. Yesterday I jumped in my RV and flew from Hobart to
Bruny Island (short flight - no problems). When I departed Bruny
Island I got a Low Voltage Warning on my EFIS a couple of minutes
after take off. I have an EXP2 Buss DC Load Center with indicator
panel and GRT EFIS. EXP2 Indicator panel showed that the Alternator
had switched off and the GRT was showing 13.3Volts and dropping.
"Dropping" is not very quantified but the initial bus voltage
excursion will be rather steep. A battery charges a 14.5 and
discharges at 12.5 . . . so the first few seconds, probably
less than a minute will show a steep drop of more than
a volt.
[]
Note that this exemplar battery loaded to 1C
starts 'working' at just over 12 volts. If he
had been fitted with a flight worthy, 17 Ah battery
and could reduce his loads to say 4A (.2C) his
trip home would have been uneventful . . .
I know you shouldn't turn the alternator off when the engine is
running however I cycled the Alt Switch to see if i could get it to
reset but no change resulted.
There is no rational prohibition for turning the alternator
on/off while the engine is running . . . particularly
if there's a flight worthy battery in service.
At this point I was over water so I requested a direct track to
Hobart and landed to check it out (while I still had some volts). By
the time I landed I didn't have enough volts to start the engine. I
recharged the battery overnight. This morning I started the engine
and the Alternator came back on line and operated as normal. After
warm ups I obtained a clearance and departed Hobart....3 mins later
the Alternator failed again and I returned to Hobart.
What's wrong with this story? After the FIRST failure of
the alternator, the battery was incapable of supporting
sustained flight for more than a few minutes.
Before I shut down I momentarily switched the master switch off and
then immediately back on - this recycled the alternator and it was
operating normally again. I suspected it may have been an over
voltage condition because the EXP2 Buss has over-volt protection
which turns off the Alternator and you have to remove battery power
to reset it. I did a ground run for approximately 3 minutes at
2200rpm but it continued to operate normally (i thought this might
cause it to fail). I shut down and removed the cowls and checked the
belt and checked the connectors. Removed and refitted the connector
on the back of the Alternator - all seemed fine. Following this I
replaced the cowls and then inspected the EXP2 Buss to see if there
were any loose connections. All seemed OK. I started the engine again
and Alternator was operating normally after run-ups and a higher rpm
check. I taxied out to the runway and I watched the indicator panel
on departure...shortly after take off (before I had reduced the rpm)
the indicator panel showed a high voltage warning which then reverted
to a low voltage warning probably due to over volt protection kicking
in. I completed the circuit and landed, tied down my RV and came to
the conclusion that I wasn't going to fly back over Bass Strait in a
hurry so I jumped on a commercial flight home.
The peek-n-poke is a good and necessary part
of the troubleshooting activity. His decision
to use alternate transportation was prudent.
We've discussed system reliability philosophies
here on the list for many years. Crafting design
goals should be followed with design, testing
and maintenance to those goals.
If this gentleman had crafted a plan-b with capable
and confident endurance (can anybody say Z-13/8?)
it's unlikely that this story would have been
written. Yes, things break on airplanes. The real
story here is not the difficulty with his alternator
or it's associated controls. It's about his
ABSOLUTE DEPENDENCE on the alternator for comfortable
transition over deep water.
So now the dilemma - I didn't bring the Alternator home with me so I
can't bench test it. My thoughts are to purchase a replacement
alternator and take it to Hobart and fit it to see if the problem
goes away. If not, then I will have a spare alternator and the
problem is more likely to be a fault in the over volt protection on
the EXP2 Buss.
Has anyone had a similar experience with the Vans 60amp Alternator
and EXP2 Buss combination? If yes - what conclusions did you come to?
I have had a previous Internal Voltage Regulator failure with this
same Alternator which was repaired. I believe the previous failure
may have been caused by turning on the alternator switch after start
up. Ever since that point I have been turning on the Alternator
switch prior to start up and turning off after shutdown.
My Engine/Alternator has now done 193 hours.
Any help/thoughts would be appreciated because when I fly back to
pick up my RV I want to be confident that I can get it home.
All the rest of this narrative is irrelevant to
the core issues illustrated. This story isn't
about resolving an alternator problem, it's about
lack of SYSTEM reliability.
Bob . . .
Message 8
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Subject: | Re: DIY CBOVM: variations on a theme |
At 10:23 AM 3/26/2014, you wrote:
>Joe,
>
>1. How much power can the dynamo produce?
Most are limited to about 30A. The single phase
(2-wire) offerings by B&C, Rotax and others
are in the 8-20A class. The 3-phase, 3-wire
devices for the larger 'tractors' can
get you 30A or so.
The problem with PM alternators is not the
power generating ability of the mechanism but
the power handling ability of the rectifier/
regulator. Unlike the 3-phase automotive
alternator that runs output power through
simple junction diodes. The regulator carries
only a couple amps of field current.
In the PM regulator, total output current of
up to 30A flows through regulator semiconductors.
Hence the heat sinks and limited size with
respect to power.
Bob . . .
Message 9
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Subject: | Re: DIY CBOVM: variations on a theme |
Ken,
Thanks for suggesting the capacitors. The circuit is stable unless the voltage
gets very close to the trip point. That is OK with me as long as there is no
nuisance tripping. Time will tell.
Good point about the crowbar circuit acting immediately by clamping the supply
to ground. The data sheet for my relay says it will operate in 15 milliseconds.
I am hoping the battery will limit the voltage until the relay contacts open.
I will try to land before the battery runs down enough (almost completely
dead) to drop out the relay.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=421078#421078
Message 10
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Subject: | Re: DIY CBOVM: variations on a theme |
Joe
600 hours on two of the OVMs and never a nuisance trip.
Have had a real trip on the Dynamo one when I started up with one of my
two small Z-14 AGM batteries dead. The totally dead battery wouldn't
accept current and the John Deere regulator immediately failed full on.
The battery did eventually charge but initially it would not accept current.
Note to self - if I leave a switch on by mistake for a week and can't
charge the battery first - at least run with that alternator off and the
batteries paralleled to the other alternator for awhile with engine
speed low enough to keep the charge current reasonable.
Ken
do not archive
On 26/03/2014 1:23 PM, user9253 wrote:
> <fransew@gmail.com>
>
> Ken, Thanks for suggesting the capacitors. The circuit is stable
> unless the voltage gets very close to the trip point. That is OK
> with me as long as there is no nuisance tripping. Time will tell.
> Good point about the crowbar circuit acting immediately by clamping
> the supply to ground. The data sheet for my relay says it will
> operate in 15 milliseconds. I am hoping the battery will limit the
> voltage until the relay contacts open. I will try to land before the
> battery runs down enough (almost completely dead) to drop out the
> relay. Joe
>
> -------- Joe Gores
>
>
Message 11
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Subject: | The lithium saga slogs onward . . . |
FIY . . . got a peek inside this battery
from True Blue Power . . . who
has achieved the first TSO'd offering for
GA aircraft.
http://tinyurl.com/lxh6wqm
The battery is 17Ah (in AIRCRAFT Ah at
1-hour - not a 20 hour rate) and 24V. Weighs
about 16 pounds. So a 12v, 17Ah battery
would be about half that weight.
TB17
This battery is an array of 56 cylindrical
cells not unlike these 26650 cells available
from a variety of sources.
1pc 3.2V LiFePO4 Li-ion LFP26650 energy type 3200mAh flat cap b
In rough numbers, this cell is a 10Wh storage
medium. 56 cells x 10Wh suggests you can expect about
560Wh from the array. This is consistent with
nameplate energy rating for the battery at 430Wh.
Being one of the few batteries where detailed
system integration data are available, we
can begin to size the task for incorporation of
this or similar products into airplanes.
A 12V version of the battery would be 215Wh
so if you have an electrically dependent engine
with a 100W service load, you could expect about
2 hours endurance for just an engine. Peel off
50-73 watts for electro-whizzies, your battery
only endurance expectations are just over 1
hour for new battery, just under 1 hour for
end-of-life battery.
Now for the sobering facts. There are two
circuit boards in the battery management system
(BMS). One is just under the heat-sink fins on
top of the battery. It's populated with a goodly
number of FAT transistors, probably N-MOS FETs
in TO-247 plastic packages.
The other board occupies a whole side of the battery
and is covered with perhaps 2-3 dozen surface mount
ic's and lots of jelly-bean parts. There's probably
more silicon in this battery than in your ICOM comm
transceiver, gps and transponder combined.
Further, I believe this battery will sell for about
$3200; so one might ball-park a 12v battery at $1600.
Of course, that's 'airplane' pricing that carries
the burden of TSO certification.
This product is the leading edge example of what it
takes to get approval for TC aviation. Other
product MIGHT offer similar capabilities for $less$
if they've not run the TSO gauntlet.
Just giving you guys a heads-up on what I'm discovering
as that battery articles move forward . . .
The REAL significance of this discovery exercise
is that to get 1-hour of battery only endurance in
a 200W airplane will take an array of 28 lithium
cells of the size cited above. This means that batteries
like this
[]
http://tinyurl.com/k8yhurl
which are 4 x 4 arrays of similar cells probably
fall short of the 1-hour endurance hypothetical
half-a-True-Blue endurance cited above.
Further, this pretty little red thing cannot feature
the same degree of battery management that's built
into the True Blue product.
Tying this back to the venerable PC680 . . .
Emacs!
We see that teh PC680 at the 1-hour rate is a 12.3Ah battery
when new. A 175W airplane will say lit up for about 45 minutes on
a new battery.
Bob . . .
Message 12
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Subject: | Re: DIY CBOVM: variations on a theme |
At 11:45 AM 3/26/2014, you wrote:
>
>In regards to stability you might check that there is a capacitor
>across the voltage reference diode and another from the SCR gate to
>ground. If you happen to have an old circuit diagram dated before
>about 2005 it may not show that update.
>
>One nice thing about the crowbar and circuit breaker in the Z
>diagrams is that the voltage is brought under control immediately
>when the SCR fires. If I understand your post it sounds like your
>implementation waits for the relay to open and for any subsequent
>arcing to extinguish. Perhaps that is good enough but it seems
>preferable to use the circuit breaker as per the Z diagrams so that
>the SCR clamps the voltage faster. Might be other small advantages
>as well such as a subsequent dead battery could not cause the
>alternator to come back on line.
For the run-of-the-mill ov conditions with a good
battery, an ov even is not one of extreme urgency.
The ships air-worthy battery will stand off a runaway
alternator for significant intervals. If one waited
100 mS to evaluate an ov condition for a true runaway
alternator, it wouldn't be a bad thing.
In fact, the next generation ov module will do just
that. Sensing an ov condition start a 100mS timer
that continue to run as long as the voltage does not
drop back below 16V before the timer runs out.
On the other hand, a second threshold at 20V assumes
no air worthy battery is present and an immediate trip
is initiated.
We're still going to pull down on the field supply
breaker . . .
Bob . . .
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