Today's Message Index:
----------------------
1. 02:48 AM - Re: EarthX battery data (Robert L. Nuckolls, III)
2. 03:31 AM - Re: EarthX lithium (Robert L. Nuckolls, III)
3. 03:48 AM - Lithium saga slogs ever onward . . . (Robert L. Nuckolls, III)
4. 06:19 AM - Re: New Over-Voltage Protection Architecture (Eric M. Jones)
5. 08:51 AM - Re: Re: New Over-Voltage Protection Architecture (Robert L. Nuckolls, III)
6. 08:53 AM - Re: Lithium batteries (D L Josephson)
7. 10:23 AM - Re: EarthX battery data (Robert L. Nuckolls, III)
Message 1
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Subject: | RE: EarthX battery data |
At 01:17 PM 3/17/2014, you wrote:
>Dear Bob,
>
>I will forward this email to our engineering department so they can answer
>your questions on a more technical level. I did review your question about
>the conflicting statements and I am not sure I understand what is
>conflicting. But maybe this will clarify....you can put gasoline in a fire
>proof container, but if it is unfortunate enough to be involved in a fire,
>it can still catch fire. We have a BMS designed to protect from overcharge
>in the applications it is designed for, but if someone uses something that
>is in absolute conflict to how our product is designed, it could be a
>problem.
Understand. Where in your marketing literature are
there defined limits beyond which the BMS is unable
to prevent catastrophic failure?
In one document I am warned that inappropriate treatment
of EarthX batteries raises risks of "rupture and/or fire"
but there are no qualified or quantified limits to what
that treatment might be.
As a designer tasked with evaluating performance,
cost of ownership and risks associated with incorporation
of your offerings into my client's system.
When I compare this page from your website . . .
Emacs!
. . . with this data published elsewhere
Emacs!
I perceive a disconnect between EarthX claim for an 80%
lighter battery (1/5th the weight of a lead-acid).
Technical literature for comparative studies of lead-acid
vs. lithium suggest that weigh savings is on the
order of 66 percent weight reduction, not 80 percent.
Is EarthX claiming some breakthrough in performance
that offers a still lighter battery?
Further, the top bubble in the image from your website
speaks to a BMS in terms that seems to imply a bullet-proof
design . . . a feature that would be very attractive to
my client . . . as long as the limits to external
abuse are quantified and the behaviors of the BMS
are known.
>Not sure if that answers your question but I have forwarded this on.
>Sincerely,
>
>Kathy Nicoson
>Global Sales Director
>(970) 301-6064
>Fax: (970) 674-9544
>www. Earthxmotorsports.com
>sales@earthxmotorsports.com
I've worked with lead-acid, ni-cad and ni-mh batteries
for decades and there are few if any features of
performance that are not well known for these
chemistries. Much is known about lithium chemistries
but the numbers and bullet-points from literature
I've read so far on EarthX products leaves many
questions unanswered.
I'd really need to understand more about the physics
and design of your products before I can recommend
them into my client's application.
I appreciate your willingness to be of assistance.
Kindest regards,
Bob Nuckolls
AeroElectric Connection
Medicine Lodge, Kansas
>-----Original Message-----
>From: Robert L. Nuckolls, III [mailto:nuckolls.bob@aeroelectric.com]
>Sent: Monday, March 17, 2014 11:54 AM
>To: sales@earthxmotorsports.com
>Subject: EarthX battery data
>
>Good afternoon,
>
>By way of introduction I am a consulting engineer with a private practice in
>a variety of markets.
>
>I retired out of Beech Aircraft in 2007 after 45+ years experience in DC
>vehicular power systems, communications, failure analysis and system
>integration.
>
>I have a client who has asked me to explore your products suitability to
>task in a new program.
>
>I need to understand how your battery management system functions. Does it
>disconnect the battery from the system when in danger of over charging or
>excessive discharging? At what voltage levels to these features assert
>themselves?
>
>I am confused by what appears to be conflicting statements on your website.
>For example: On these two pages
>
>http://tinyurl.com/qex9gbg
>
>http://tinyurl.com/nxzf7r2
>
>I see statements that imply management of battery overcharge events by the
>BMS . . . but on the other page, we are cautioned about mis-applied chargers
>offer risks for battery rupture and/or fire.
>
>If an EarthX battery is inadvertently discharged too deeply, I presume the
>BMS will shut off current flow below some level . . . what are the limits
>for remaining in this discharged state in terms of recovering battery
>performance? Your website literature speaks to 4000 cycles . . . what depth
>of discharge is tolerated by EarthX batteries to meet the 4000 number? What
>capacity fraction used to benchmark end of life after 4000 cycles?
>
>I'm seeking engineering test data on energy content and internal impedance
>of the various EarthX products. In particular, a data sheet not unlike this
>document describing performance for a Panasonic SVLA battery . . .
>
>http://tinyurl.com/pjgzewx
>
>This format and detail of data will allow me to service my customer with a
>well considered decision on EarthX products for suitability to task.
>
>It would be very useful to have a contact name and email for an individual
>at EarthX who can supply needed data and carry on a dialog for any future
>questions.
>
>Kindest regards,
Bob . . .
Message 2
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Subject: | Re: EarthX lithium |
At 02:01 PM 3/17/2014, you wrote:
Bob N,
LiFePo battery - AeroVoltz 8 Cell Lithium Battery. http://aerovoltz.net/en/
The Sport EFIS consumes about 1 amp according to the
documentation. I don't have good numbers on the GRT EIS4000 but I
would allow about 1 amp with all the sensors, back light, display,
etc. I may be able to get a better number next trip to the
hanger. The radio and transponder are MicroAir M760Q & T2000
SFL. From the documentation, I'd say they each use about 250-300ma
with the backlight on and not transmitting.
The battery turned the 914 over very smartly. The engine is easy to
start in any case so it wasn't really working that hard. Three or 4
prop blades and it starts. That's 2 or 3 rotations of the engine.
Okay, that's not an EarthX battery which
claims to have a battery management system
built in.
From the physical sizes of these batteries,
I suspect they are assembled from individual
cells not unlike the 26650 styles offered by
A123 and others.
http://tinyurl.com/ktyfbnp
These would be 'rated' at something on the
order of 2.3 to 2.5aH per cell. A 2-row,
8-cell assembly would offer a 12V battery
with a capacity on the order of 5aH. A number
which is inconsistent with your battery
only endurance experience.
Their 16-cell product would have a cell weight
of 75g x 16 or 1.2Kg. Their catalog weight for
the 16 cell product is 1.6Kg which leaves 0.4Kg
for enclosure . . . sounds about right. So
their 16-cell product would clock in with a 10aH
legacy rating and 1.2Kg x 125Wh/Kg or 150Wh
of total energy.
Given the relatively flat discharge curves of
lithium chemistries (low internal impedance) one
might estimate that 125Wh will be available at
a 10A discharge rate. So it seems that the 16-cell
device would run a 100W demand engine for 1.2 hours
when new and 1 hour at end of life.
Let's get some hard numbers on the current draw
for your experiments and see why you didn't get
better performance from your '5aH' product.
Aerovolts doesn't claim to offer an
internal BMS but they do offer the external
BMS charger with words like:
------------------------------------
The Aerovoltz Battery Management System Balance Charger is the only
charger on the market designed specifically to work with the
Aerovoltz battery. The primary advantage to the Aerovoltz BMS Blance
Charger is the balance charging function. The Balance mode balances
the voltage of each cell or cell pack while charging. By balance
charging your Aerovoltz Performance Battery you insure that the
battery is operating at its maximum power. Periodic balance charging
can also double the expected life of your battery. This charger is
not required to operate your Battery, but it is highly recommended.
The only charger made to work with the Battery Management System.
Plugs directly into the batteries BMS port.
Able to balance charge all the cells individually for max
power and durability.
Can double the expected life of the battery.
Has Charge, Fast Charge, Balance Charge, and Storage Charge
Functions.
Available in 120V (US) and 240V (EUR).
-------------------------------------
The problem I have with these special chargers is
rooted in the fact that when we put an airplane away,
the battery is generally topped off . . .
It's my understanding that these super-smart chargers
work their magic while recharging a partially to
completely depleted battery. How then would such a
charger benefit the OBAM aircraft owner/operator?
. . . and DOUBLE the life of the battery? THAT'S
a VERY LONG POLE in the tent for cost-of-ownership
for a battery that is already VERY expensive compared
to the device it purports to replace.
Aerovolts also claims:
-----------------------------------------
The 16 Cell has a massive 500PCA and 28 Pbeq AHs at only 3 lbs of
weight. The 16 Cell is a direct replacement of the Yuasa YTX30L-BS,
GYZ-20HL, and YTX24HL-BS.
-----------------------------------------
The Yuasa YTX30L is a 22 pound, SVLA battery that would
clock in at about 24aH . . . I submit that while the 16-cell
Aerovolts product may CRANK like the Yuasa battery, it is
NOT A DIRECT REPLACEMENT when it comes to keeping the
fires lit up front . . . in fact, it's probably less than
half the capacity of the Yuasa battery.
Emacs!
We'll keep asking questions . . .
Bob . . .
Message 3
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Subject: | Lithium saga slogs ever onward . . . |
I downloaded the detail spec sheet for A123 26650
cells at . . .
http://tinyurl.com/n73f9gj
This cell and others like it seem to be the core
ingredient of choice for many of the off-the-shelf
battery products that are cropping up everywhere.
There's an interesting graphic in this data sheet . . .
Emacs!
Notice that the family of curves acknowledges the fact that this cell,
like all other sources of energy, has a source impedance. This is
illustrated by the fact that heavier loads produce initial plots on
the curve that are successively lower in voltage as the load current
rises. I.e., the higher the load, the higher will be I(squared)R
energy losses due to internal heating.
But then something magic happens. All three plots come together
at just under 2.5aH . . . gee . . . where did all those wasted
Watt-seconds go during discharge but magically showed up again
before the cell dropped below 2V?
Can't believe much that you read in the papers . . . gotta
be careful about data sheets too . . .
Bob . . .
Message 4
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Subject: | Re: New Over-Voltage Protection Architecture |
Joe,
Before you reinvent anything, let me show you my Proposed Perihelion Power Protector
(attached).
Repost from 20JUL07: (time flys...)
I talk to many builders who are particularly concerned about frying their expensive
avionics and glass panels. These parts are typically 1/3 of the airplane
cost.
Planning the wiring of a small aircraft involves installing systems to safeguard
the buses against failure of the alternator. Either an internally regulated
alternator or its more adaptable brother with an external regulator still has
the potential problem of a runaway condition, as well as a short circuit of the
main battery to alternator B-lead, and frequent load dump OV conditions.
A solution is herein proposed
Linear Technology has introduced a clever device, the LT4356-1 Overvoltage Protection
Regulator and Inrush Limiter to address all these worries. Not only thatthey
list Automotive/Avionic Surge Protection is one of its chief applications.
The LTC approach takes the high voltage from a load dump or failed alternator and
REGULATES it while the situation is being tamed. The IC package is 3mm X 4mm
and drives a big N-MOSFET that does the heavy work of regulating the voltage.
So what happens? Normally the alternator current is carried by the fully on N-MOSFET.
Assume the current is 50A, and the Rds(on) is 0.012 ohms. The dissipation
would be only 30W. This is easy to handle with a reasonable heat sink.
Assume the alternator and/or the regulator goes cuckoo. This could happen if the
alternator field winding shorts to the B-lead output or the sense lead in the
regulator opens, or other untoward goings-on. The alternator output goes into
an upward voltage spiral. This voltage is not unlimited, especially if there
is a load on it, but could be 80 VDC.
Now the LT4356-1 REGULATES the output via the big N-MOSFET on a heat sink. The
aircraft buses never sees more than 14.5 Volts (or whatever is desired). This
is true for the short time (500 mS) load dumps, and it will regulate a runaway
alternator for a time determined by whatever the N-MOSFET and heat sink can dissipate.
The LT4356-1 has a timer circuit to protect the N-MOSFET. If the time expires and
the stress continues, the fault warning signals an impending power-down and
the N-MOSFET shuts off the B-line.
Additionally, some models of the LT4356-1 have a spare amplifier/comparator that
can be used for any purpose (not shown here). It operates from 4 to 80 VDC,
and withstands 30V and up to 100V. A series low voltage P-MOSFET or a Schottky
diode can be added to protect against a shorted alternator that would draw reverse
current. The device has built-in protection again high current shorts of
the B-Line to the battery.
The drawing shows a basic form. A few additional parts are necessary. However,
consider the parts that WOULDNT be necessary:
The B-Line contactor,
The OV monitor,
The load dump preventer,
The B-Line fuse,
The alternator switch.
No crow bar or linear over voltage switch.
I dont have current plans to market this but will build one for myself.
Discussion is invited.
See attachment for a pdf version of this note with drawing.
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=420541#420541
Attachments:
http://forums.matronics.com//files/power_good_a1_176.pdf
http://forums.matronics.com//files/power_protector_schematic_383.pdf
http://forums.matronics.com//files/power_protector_revb_419.pdf
Message 5
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Subject: | Re: New Over-Voltage Protection Architecture |
At 08:17 AM 3/18/2014, you wrote:
Joe,
Before you reinvent anything, let me show you my Proposed Perihelion
Power Protector (attached).
Repost from 20JUL07: (time flys...)
I talk to many builders who are particularly concerned about frying
their expensive avionics and glass panels. These parts are typically
1/3 of the airplane cost.
Planning the wiring of a small aircraft involves installing systems
to safeguard the buses against failure of the alternator. Either an
internally regulated alternator or its more adaptable brother with an
external regulator still has the potential problem of a runaway
condition, as well as a short circuit of the main battery to
alternator B-lead, and frequent load dump OV conditions.
"frequent"?
Linear Technology has introduced a clever device, the LT4356-1
Overvoltage Protection Regulator and Inrush Limiter to address all
these worries.
. . . but are they real worries . . .
We had an extended discussion on 'load dumps' here
on the List back about 2004. A sampling of the
work product during those conversations can be
accessed at . . .
http://tinyurl.com/ngu7ptq
Load dump speaks to the naturally occurring response
of the engine driven power source, its regulator
and perhaps the ship's battery to a sudden reduction of a
large load . . . like an air conditioner pump
motor, landing gear hydraulic pump motor, etc.
Another case supposes that a battery is not present
or becomes UNHOOKED during this heavy-load reduction.
Not only does the alternator/generator become suddenly
UNLOADED . . . the system may also be deprived of it's #1
load dump MITIGATOR . . . the battery.
This condition is addressed in DO-160/Mil-STD-704
as a recommendation designing a 14v product to
stand off 20V for 1S, 40V for 100mS. Double the
voltages for a 28V system. This is the time
it takes for an equally qualified OV management
system to corral the aberrant energy source and
bring the event to a graceful conclusion.
You will find the LT4356 cited in the constellation
of Google hits in the link cited above. This device
is but one of MANY approaches to achieving load-dump
robustness in aircraft. I've been testing to DO-160/
Mil-STD-704 for 40+ years and never found it necessary
to go to such extremes in parts count to protect the
input power port of my proposed appliance.
I'm not suggesting that the LT4356 does not perform
as advertised but I will suggest that it's an
inelegant solution to a problem that been the least
of our design challenges for decades.
I suggest that load-dump stresses that fall outside
the time honored design goals don't happen . . .
Recall how many times I've written about the paucity
of accidents having root cause in electrical system
issues. Of the few which did have electrically fertilized
roots, load-dump damage was not among them.
Further, how many installation manuals for your $high$ electro-
whizzies suggest any need to mitigate transient effects
above and beyond the DO-169 stresses to which they
have already qualified their product?
Can you imagine the cries out of the darkness and
renting of clothes should some big name like Garmin
hold forth with such a recommendation? Such an
assertion would mean one or both of two things (1)
DO-160 was found lacking or (2) Garmin was unable to
design to DO-160 design goals. You would be less
scorned if they predicted that the sun would rise
in the north tomorrow or that water molecule of H3O2
is predicted to freeze at 50C.
I did a pitch trim controller for the Lear 30/50
series airplanes that would stand off 80 volts for
tens if seconds . . . not milliseconds . . . it was no
big deal. My biggest challenge in that design was
to beat the parts count down in a worry-mitigation
watch-dog with about twice the parts count
of the controller. Over the years, failures in the
system were predominantly in the watch-dog
. . . not the controller.
The point being that one should be cautious when
taking on new worries about spikes, surges, bumps,
dumps, wiggles and jiggles on the bus that have
been pretty well understood for a long time. We
can look back at pyramid builders and marvel at
their cleverness and knowledge . . . but for them
it was all in a day's work.
http://tinyurl.com/n3swgjr
For those of us who made a vocation of simple, low cost,
robust designs in electrical systems . . . it's
all in a days work. The simple ideas upon which that
work is based is timeless, unchanging and indestructible.
Only the chefs and the recipes for success change . . .
hopefully for the better.
Bob . . .
Message 6
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Subject: | Re: Lithium batteries |
Perhaps those who have had LiFePO4 or other lithium batteries fail after
deep discharge would be willing to disassemble the various brands and
report what they find inside. This would possibly be more useful than
asking the sales people from the battery packagers for data they don't
wish to reveal.
I have been working with several groups who are researching electric
aircraft. The energy density and other characteristics of the available
cells are well known; at best a packaged battery is the sum of the cells
inside. If there is a BMS there are three simple questions to ask: is
there a low voltage disconnect during discharge, is there a high voltage
disconnect during charge, and how many cells are monitored together in
determining these voltages?
--
David Josephson
Message 7
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Subject: | RE: EarthX battery data |
At 11:23 AM 3/18/2014, you wrote:
>Dear Bob,
>
>I do thank you for your input and responses and
>as this is a virgin market for us, based on the
>experimental aircraft market seeking us out, we
>are re-evaluating our labeling, our manual, and
>questions that need to be answered and really do appreciate your feedback.
>
>Our batteries were designed and marketed towards
>the power sport market and our website is geared
>towards customers, not engineers or OEM
>manufacturers, but we do have this data and will
>incorporate the needed information so our
>customers can make an informed decision.
Okay, I can help you with that effort.
I have written dozens of product performance
specifications for products that fly on
both commercial and military airplanes.
>
>
>As far as the 80% lighter=85=85.all lead acid
>manufacturers have different weights on the same
>lead acid replacement battery and then will also
>list different weights on the exact same lead
>acid battery out there. For example, the PC680
>is listed as 15.4 pounds on the Odyssey website,
>it is listed as 14.8 pounds on an Amazon listing
>and it is listed as 16 pounds on Battery Mart
>website. Another lead acid battery that is
>recommended to replace a PC680 is the Big Crank
>ETX30L which weighs 23 pounds. And of course,
>you can find different weighs listed for this
>battery as well but for simplicity, I will use the 23 pounds.
Yes, but you're not considering ALL of the
features for equivalency. I note that the
lithium chemistry entrepreneurs are fond
of the term "Lead-Acid Equivalency". It appears
that this term was invented out of whole
cloth to assert, "This lithium battery cranks
an engine as well as that lead-acid battery."
This is a useful term for folks interested only
with getting an engine started. I suggest to you
that airplanes are another matter entirely.
Airplanes have complex instrumentation, navigation
and communications requirements that need to be
powered when and if the alternator fails.
A smaller number of airplanes also feature electronically
managed engines with significant energy demands
on the order of 100 watts. If one expects to
sustain flight under battery-only conditions,
a common design goal is 1 hour of endurance,
2 hours would be MUCH better.
Hence, it is critical that your marketing literature
include data not unlike that which I cited for
the Panasonic lead-acid batteries. If you want
to drop into a battery box once occupied by a PC680,
consider the following data offered by Hawker/Enersys
concerning the performance of that battery . . .
http://tinyurl.com/ng9jhua
Emacs!
The PC680, when new, will carry a 130 watt demand
for one hour . . . only 45 minutes at end of battery
life.
Hawker/Enersys doesn't have a 22 pound battery
(10Kg) in that style, but if they did, it would
offer about 10/7 or about 1.4 times the capability
of the PC680.
What is the one-hour delivery capability of your
3.5 pound battery?
>
>The battery the we recommend to replace this
>battery is 3.5 pounds, for a 77-78% weight
>savings, depending on what weight you want to
>use compared to the Odyssey battery and 85%
>lighter than the Big Crank. We do list the
>actual weight in our battery spec=92s page on the
>website and it someone really needs to know the
>exact percent weight savings on the battery they
>are using for their application, they will have
>to do the math and get a real weight of the lead
>acid battery they are using compared to
>ours. Therefore, we do not feel there is a
>disconnect on our claim that we can be 80% lighter.
BUT . . . while your 3.5 pound offering will start
the engine as smartly as the 22 pound example, the
3.5 pound battery CANNOT support critical electronics
for the same time as the 22 pound battery.
For this reason, I counsel caution with respect to
that PbEq number. There's no engineering validation
for the term in an aviation market. Unfortunately,
most DIY airplane builders are NOT well versed in
the legacy terminology . . . much less new terms
created to promote the low internal impedance of
lithium cells.
Based on the above assertions, I suggest there is
a huge disconnect when you're talking to builders
and maintainers of personal aircraft. Assertion of
this equivalency at Cessna, Beech, Mooney or Piper
would probably get you more than raised eyebrows.
>
>And again, I have forwarded this to our
>engineering department and when they are able,
>they will get back to you or provide me with the answers to your questions.
>
>
>Sincerely,
>
>
>Kathy Nicoson
>Global Sales Director
>(970) 301-6064
>Fax: (970) 674-9544
>www. Earthxmotorsports.com
>sales@earthxmotorsports.com
Very well. Looking forward to it. Please convey
my willingness to be of assistance in crafting
competent and lucid literature for marketing
to aviation.
Kindest regards,
Bob . . .
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