Today's Message Index:
----------------------
1. 09:13 AM - Re: Some interesting observations (Bob Verwey)
2. 12:40 PM - B&C SD-8 Alternator/Regulator (Ron Springer)
3. 02:29 PM - Re: B&C SD-8 Alternator/Regulator (Robert L. Nuckolls, III)
4. 02:29 PM - Re: Some interesting observations (Robert L. Nuckolls, III)
5. 03:27 PM - Re: B&C SD-8 Alternator/Regulator (Ron Springer)
Message 1
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| Subject: | Re: Some interesting observations |
Bob I am often in awe of your energy in serving the OBAM community..thank
you for your missives, they inspire neophytes like me to get "electron
savvy"
Best Regards,
Bob Verwey
082 331 2727
On Mon, 24 Aug 2020 at 22:56, Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> I've been gathering test data on some lithium products
> in anticipation of doing an article on the quest for
> an elegant integration of lithium cells into OBAM
> light aircraft.
>
> The two attached plots are interesting. The test article
> is an EarthX ETX26D graciously donated to our 'cause' about
> 6 years ago. The plots illustrate battery behavior when
> subjected to an array of charge/discharge profiles.
>
> In the charge plots we see the battery response to
> being charged in 0.5 volt steps over the range of 13.0
> to 15.0 volts.
>
> The 15.0 and 14.5 volt curves show a marked inflection
> of charge current approx 2 hours after starting the
> test. As the charge voltage is lowered, the inflections
> (achievement of full charge) move outward in time and
> are less pronounced. The interesting plot is at 13.0
> volts . . no inflection . . . i.e. the battery doesn't
> take on any charge.
>
> The discharge plots are equally interesting. Note that
> 13.0v charge pumped no appreciable energy into the
> battery chemistry. However, charging at 13.5 to 15.0
> volts fully charges the battery. i.e. the battery
> performance (except perhaps for charging time)
> is unaffected by bus voltage. Note: the red plot
> is what the battery delivered 'off the shelf' after
> having been used/stored/maintained at intervals
> over the past 5 or so years.
>
> I not that the battery's demonstrated capacity is
> on the order of 10.3 AH . . . down slightly from
> demonstrated 11.6 AH when received as new.
>
> These data are consistent with an article I
> found on powerstream.com
>
> https://tinyurl.com/yakthgt6
>
> Where the author demonstrates the profound difference
> in performance between Lithium Iron versus the
> Lithium Polymer products. The article shows how the popular
> and quite common Lithium Polymer cells fully charge at
> 4.2 volts with stored energy profoundly affected by
> the top-off voltage. Same goes for Lithium Ion cells
> widely offered as rechargeable power for a constellation
> of consumer products.
>
> Touchstone of note: No matter what claims are made
> for the capacity of these cells, the real capability
> of an 18650 Li-Ion cell is on the order of 2800 mAH. This
> is easily confirmed by studies of published engineering data
> sheets for name brand cells like Panasonic, A123,
> Sanyo, etc.
>
> https://tinyurl.com/y32rh8ym
>
> Those ads on eBay touting 4000-10,000 mAH are blowing
> smoke up your pant leg. Now, I not implying that
> these cells are not serviceable products . . . price/
> performance can be quite good but unless verified
> by published performance data sheets, be skeptical
> of stellar capacity claims.
>
> That leaves us with the lowly Lithium Iron Phosphate
> cell. It has the poorest capacity for unit volume of
> all the popular products . . . but they are relatively
> immune to catastrophic failure. Hence, the chemistry
> of choice for the 'big guys' in TSO batteries for
> CT aircraft. Typical energy ratings for the 18650
> LiFePO4 are on the order of 1000-1500 mAH.
>
> A noteworthy fallout of my studies suggests there
> is no value in running the bus at any higher
> than 14.0 volts for the LiFePO4 products.
>
> Just thought I'd share some of the the bucket
> of data point's I've gathered so far . . .
> I'm still pondering the burned alternator
> coils on the Revmaster engine . . . got some
> ideas I want to massage on the test bench . . .
>
>
> Bob . . .
Message 2
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| Subject: | B&C SD-8 Alternator/Regulator |
Due to some strange behavior on my EFIS shortly after takeoff, I theorized
that I might have a noisy electrical system that was causing EFIS problems.
The charging system (SD-8) doesn't kick in until I take off and achieve
higher RPM. I could not reproduce the problem on the ground so I could not
easily hook up an oscilloscope. Maybe because static runs don't achieve the
same RPM at full throttle, and high speed taxi runs on a 3000 ft runway
achieve higher RPM but don't last long enough?
So, I did another flight and took off and when the problem happened again,
I turned off the alternator so I was just running on the battery. The EFIS
problems continued so I don't believe I have a noisy electrical system
causing the problem. I also swapped out the regulator and replaced the
battery just to be thorough!
My real question is related to what happens when I disconnect a PM
alternator from the electrical system between the regulator and the bus.
Does it keep generating 8 amps that now has to be dissipated as heat by the
voltage regulator? I did notice some noise, or a change in the noise, in my
headset when I disconnected the alternator/regulator.
Also, what would happen if I disconnected the two leads for the alternator
so that they weren't even connected to a regulator?
Thanks,
Ron
Message 3
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| Subject: | Re: B&C SD-8 Alternator/Regulator |
At 02:35 PM 8/25/2020, you wrote:
>Due to some strange behavior on my EFIS shortly
>after takeoff, I theorized that I might have a
>noisy electrical system that was causing EFIS problems.
Is this a new condition or has always
existed?
>The charging system (SD-8) doesn't kick in until
>I take off and achieve higher RPM. I could not
>reproduce the problem on the ground so I could
>not easily hook up an oscilloscope. Maybe
>because static runs don't achieve=C2 the same RPM
>at full throttle, and high speed taxi runs on a
>3000 ft runway achieve higher RPM but don't last long enough?
Fair hypothesis . . .
>So, I did another flight and took off and when
>the problem=C2 happened again, I turned off the
>alternator so I was just running on the battery.
>The EFIS problems continued so I don't believe I
>have a noisy electrical system causing the
>problem. I also swapped out the regulator and
>replaced the battery just to be thorough!
Good . . .
>My real question is related to what happens when
>I disconnect a PM alternator from the electrical
>system between the regulator and the bus. Does
>it keep generating 8 amps that now has to be
>dissipated as heat by the voltage regulator? I
>did notice some noise, or a change in the noise,
>in my headset when I disconnected the alternator/regulator.
Depends on the pedigree of the regulator.
Some designs do indeed 'short' the alternator
windings to regulate power at the battery.
When ship's systems are using power, the need
to short-out excess energy is minimized. But
you're right, if this is a shunt style R/R,
reducing output current to zero MAY cause
the regulator to severely abuse the alternator
mistakenly thinking that ship's loads are still
there . . . just very small.
>Also, what would happen if I disconnected the
>two leads for the alternator so that they
>weren't even connected to a regulator?
Conduct the experiment. Opening the AC power
BETWEEN alternator and rectifier/regulator is
the preferred method for shutting down the
system. All energies in the alternator
system go to zero. See:
https://tinyurl.com/7vp9g4e
Unhook the alternator and do a battery only
flight.
Bob . . .
Message 4
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| Subject: | Re: Some interesting observations |
At 11:06 AM 8/25/2020, you wrote:
>Bob I am often in awe of your energy in serving the OBAM
>community..thank you for your missives, they inspire neophytes like
>me to get "electron savvy"
>Best Regards,
>Bob Verwey
>082 331 2727
To be inspiring is a teacher's prime
directive . . . thank you sir.
Bob . . .
Message 5
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| Subject: | Re: B&C SD-8 Alternator/Regulator |
On Tue, Aug 25, 2020 at 5:34 PM Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> At 02:35 PM 8/25/2020, you wrote:
>
> Due to some strange behavior on my EFIS shortly after takeoff, I theorized
> that I might have a noisy electrical system that was causing EFIS problems.
>
>
> Is this a new condition or has always
> existed?
>
I thought it was a new condition. My plane has been down for quite a while
during an engine rebuild. I am trying to fly it and monitor temperatures on
my new engine but all the engine data is fluctuating wildly. I looked back
at some old data and I could see the same symptoms occasionally, but it was
more mild and very infrequent. I just never noticed it. Now, it is
happening nearly continuously and the variations are far more extreme. The
EFIS has three other issues as well. It has lost the GPS signal, it always
stops recording data to the USB stick once the temperature oscillations
start, and it only sometimes displays the ADSB-in data that I am feeding
it. One thing in common with all of these is that they are connected to
serial ports on the EFIS. Either four things just simultaneously failed or
there is a problem with the EFIS serial ports. That's my current theory.
> Also, what would happen if I disconnected the two leads for the alternator
> so that they weren't even connected to a regulator?
>
>
> Conduct the experiment. Opening the AC power
> BETWEEN alternator and rectifier/regulator is
> the preferred method for shutting down the
> system. All energies in the alternator
> system go to zero. See:
>
> https://tinyurl.com/7vp9g4e
>
> Unhook the alternator and do a battery only
> flight.
>
Yes, that is exactly what I am planning for the next flight. Additionally,
the EIS is remotely mounted but it has a display. I intend to fly with a
GoPro aimed at it to see if the CHT values that it displays match those on
the EFIS. If there is simply a communication problem or some source of
noise in the EFIS, then the EIS should be displaying the correct CHT values
and not wildly fluctuating.
Ron
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