Today's Message Index:
----------------------
1. 12:22 PM - lithium facts (Robert L. Nuckolls, III)
2. 01:57 PM - Re: lithium facts (Stuart Ashley)
3. 02:16 PM - Re: lithium facts (B Tomm)
4. 03:13 PM - Re: lithium facts (Robert L. Nuckolls, III)
5. 04:08 PM - Re: lithium facts (Ken Ryan)
6. 04:32 PM - Re: lithium facts (Robert Borger)
7. 05:18 PM - Re: lithium facts (Ken Ryan)
Message 1
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I've been working on a series of articles for Kitplanes
on the use of lithium batteries in airplanes. Energetic
concerns for making the switch are centered on the extra-
ordinary ability of lithium batteries to catch fire . . .
and set other things on fire too. But then, we went through
similar gyrations of risk assessment and design goals with
the NiCad batteries wwwaaayyyy back when too.
I've been 'playing' with some exemplar cells on the bench
and putting some pretty good miles on my battery-runner-downer-
machine. An interesting feature of this chemistry has bubbled
to the top of my attention. While the Lead-Acid cell chemistry
'tops off' at about 2.4 volts per cell, the lithium cells top
off at 4.2 volts.
Hmmmm . . . so if your electrical system is already designed
around a six-cell lead-acid storage medium with regulator
set to accommodate a 14.4v for topping off lead-acid, how many
cells should the Li-Ion replacement feature . . . and what
changes, if any, should be made to the regulation set-point?
A 3-cell lithium battery gets fully stuffed at 12.6 volts,
a 4-cell array would like to see 16.8 volts. Hmmmm . . .
what's the elegant design goal? We've read in the journals
that the hybrid car guys design their charge-discharge
profiles to operate state-of-charge over a range of 20-80%
to maximize the battery's service life. What happens if
we charge a 4-cell array at 14.4/4 or only 3.6 volts per
cell?
Turns out, this top-off voltage will take a lithium cell to
about 50% of potential capacity of the chemistry. Obviously,
adjusting the regulator on your airplane to 16.0 volts or
more has some serious implications for the rest of the ship's
electro-whizzies. Okay, perhaps we're dollars/weight ahead
by operating a 4-cell array in an un-modified lead-acid system.
That makes for good service life, right?
Maybe, NOW we're talking about 0% to 50% cycle limits on
the lithium product . . . we know that lithium really detests
over-discharge events. How does 0->50 compare with 20->80
favored by the guys who use lithium in cars? Dunno . . . yet.
Don't want speak out of ignorance or get out in front of
the article's completion . . . but it's becoming somewhat
obvious that the 'lead-acid equivalency' cited by marketers
of lithium is less than forthcoming. Yeah, lithium
has 3x the energy density of lead-acid when topped-off. But
if the lead-acid set point charges the battery to only 50%, you
just tossed off the top half of the battery's energy storage
potential.
The upside of this fact suggests that there is no way
that a lithium battery is going to be 'abused' by an
alternator set for 14.4 volts. If an installed lithium
battery goes into energetic self destruction it will have
to be triggered by some stress other than voltage; high-rate
discharge or design/manufacturing failure internal to a cell.
Something to ponder guys . . . watch this space . . .
Bob . . .
Message 2
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| Subject: | Re: lithium facts |
Hi Bob;
I have heard, but have no personal experience, that the danger of fires
from lithium iron batteries is much reduced in comparison to lithium ion
batteries, while their weight is only slightly greater. So one of my
questions is: With which type of battery are you experimenting? If it's
not lithium iron, I suggest you get one of those too. My second point is:
Could a simple solid state DC voltage regulator be designed to bring the
16.8 V. down to 14.4 V.? This would maximize the potential of the lithium
battery. I have read the AeroElectric Connection through a second time
and really appreciate the work you do.
Cheers! Stu.
On Sun, Nov 2, 2014 at 12:21 PM, Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> nuckolls.bob@aeroelectric.com>
>
> I've been working on a series of articles for Kitplanes
> on the use of lithium batteries in airplanes. Energetic
> concerns for making the switch are centered on the extra-
> ordinary ability of lithium batteries to catch fire . . .
> and set other things on fire too. But then, we went through
> similar gyrations of risk assessment and design goals with
> the NiCad batteries wwwaaayyyy back when too.
>
> I've been 'playing' with some exemplar cells on the bench
> and putting some pretty good miles on my battery-runner-downer-
> machine. An interesting feature of this chemistry has bubbled
> to the top of my attention. While the Lead-Acid cell chemistry
> 'tops off' at about 2.4 volts per cell, the lithium cells top
> off at 4.2 volts.
>
> Hmmmm . . . so if your electrical system is already designed
> around a six-cell lead-acid storage medium with regulator
> set to accommodate a 14.4v for topping off lead-acid, how many
> cells should the Li-Ion replacement feature . . . and what
> changes, if any, should be made to the regulation set-point?
>
> A 3-cell lithium battery gets fully stuffed at 12.6 volts,
> a 4-cell array would like to see 16.8 volts. Hmmmm . . .
> what's the elegant design goal? We've read in the journals
> that the hybrid car guys design their charge-discharge
> profiles to operate state-of-charge over a range of 20-80%
> to maximize the battery's service life. What happens if
> we charge a 4-cell array at 14.4/4 or only 3.6 volts per
> cell?
>
> Turns out, this top-off voltage will take a lithium cell to
> about 50% of potential capacity of the chemistry. Obviously,
> adjusting the regulator on your airplane to 16.0 volts or
> more has some serious implications for the rest of the ship's
> electro-whizzies. Okay, perhaps we're dollars/weight ahead
> by operating a 4-cell array in an un-modified lead-acid system.
> That makes for good service life, right?
>
> Maybe, NOW we're talking about 0% to 50% cycle limits on
> the lithium product . . . we know that lithium really detests
> over-discharge events. How does 0->50 compare with 20->80
> favored by the guys who use lithium in cars? Dunno . . . yet.
>
> Don't want speak out of ignorance or get out in front of
> the article's completion . . . but it's becoming somewhat
> obvious that the 'lead-acid equivalency' cited by marketers
> of lithium is less than forthcoming. Yeah, lithium
> has 3x the energy density of lead-acid when topped-off. But
> if the lead-acid set point charges the battery to only 50%, you
> just tossed off the top half of the battery's energy storage
> potential.
>
> The upside of this fact suggests that there is no way
> that a lithium battery is going to be 'abused' by an
> alternator set for 14.4 volts. If an installed lithium
> battery goes into energetic self destruction it will have
> to be triggered by some stress other than voltage; high-rate
> discharge or design/manufacturing failure internal to a cell.
>
> Something to ponder guys . . . watch this space . . .
>
>
> Bob . . .
>
>
Message 3
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Thanks Bob,
We knew you could lift the veil on the prospective new bride. Curious to see
what she looks like. From which clan is she... LiFe or LiFePo? :)
Bevan
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L.
Nuckolls, III
Sent: Sunday, November 02, 2014 12:22 PM
Subject: AeroElectric-List: lithium facts
--> <nuckolls.bob@aeroelectric.com>
I've been working on a series of articles for Kitplanes on the use of
lithium batteries in airplanes. Energetic concerns for making the switch
are centered on the extra- ordinary ability of lithium batteries to catch
fire . . .
and set other things on fire too. But then, we went through similar
gyrations of risk assessment and design goals with the NiCad batteries
wwwaaayyyy back when too.
I've been 'playing' with some exemplar cells on the bench and putting some
pretty good miles on my battery-runner-downer- machine. An interesting
feature of this chemistry has bubbled to the top of my attention. While the
Lead-Acid cell chemistry 'tops off' at about 2.4 volts per cell, the lithium
cells top off at 4.2 volts.
Hmmmm . . . so if your electrical system is already designed around a
six-cell lead-acid storage medium with regulator set to accommodate a 14.4v
for topping off lead-acid, how many cells should the Li-Ion replacement
feature . . . and what changes, if any, should be made to the regulation
set-point?
A 3-cell lithium battery gets fully stuffed at 12.6 volts, a 4-cell array
would like to see 16.8 volts. Hmmmm . . .
what's the elegant design goal? We've read in the journals that the hybrid
car guys design their charge-discharge profiles to operate state-of-charge
over a range of 20-80% to maximize the battery's service life. What happens
if we charge a 4-cell array at 14.4/4 or only 3.6 volts per cell?
Turns out, this top-off voltage will take a lithium cell to about 50% of
potential capacity of the chemistry. Obviously, adjusting the regulator on
your airplane to 16.0 volts or more has some serious implications for the
rest of the ship's electro-whizzies. Okay, perhaps we're dollars/weight
ahead by operating a 4-cell array in an un-modified lead-acid system.
That makes for good service life, right?
Maybe, NOW we're talking about 0% to 50% cycle limits on the lithium product
. . . we know that lithium really detests over-discharge events. How does
0->50 compare with 20->80 favored by the guys who use lithium in cars? Dunno
. . . yet.
Don't want speak out of ignorance or get out in front of the article's
completion . . . but it's becoming somewhat obvious that the 'lead-acid
equivalency' cited by marketers of lithium is less than forthcoming. Yeah,
lithium has 3x the energy density of lead-acid when topped-off. But if the
lead-acid set point charges the battery to only 50%, you just tossed off the
top half of the battery's energy storage potential.
The upside of this fact suggests that there is no way that a lithium battery
is going to be 'abused' by an alternator set for 14.4 volts. If an installed
lithium battery goes into energetic self destruction it will have to be
triggered by some stress other than voltage; high-rate discharge or
design/manufacturing failure internal to a cell.
Something to ponder guys . . . watch this space . . .
Bob . . .
Message 4
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| Subject: | Re: lithium facts |
At 15:55 2014-11-02, you wrote:
Hi Bob;
I have heard, but have no personal experience, that the danger of
fires from lithium iron batteries is much reduced in comparison to
lithium ion batteries, while their weight is only slightly greater.
To be sure, there are big differences in how the various
chemistries behave AFTER the fire starts . . . but all
battery chemistries from lead-acid to ni-cad, to lithium
store a lot of energy in a relatively small volume. So
all chemistries present some hazard for rapid release of that
energy to varying degrees. Even the out-gassing products
of Li-Iron are combustible. This is why the True Blue batteries
[]
. . .
have those little 'smoke stacks' on top. They connect to a
vent tube designed to take the nasties over-board in the event
of catastrophic failure within a case DESIGNED to contain
such events.
To test the integrity of the case, the protective features
of the battery management system (BMS) are disabled and
the test lab puts 42 volts to the array of cells. After
a period of time, a 'fog' of nasties begins to pour from
the vent but case temperatures remain quite nominal . . .
non-hazardous to children and other living things aboard
the airplane.
The design philosophy calls for getting this electronic version
of nitro-glycerine packaged in a manner that contains
worst-case failures . . . Damn I love FMEAs! Fooey on that
reliability study stuff . . . assume the worst and tame it.
So one of my questions is: With which type of battery are you
experimenting? If it's not lithium iron, I suggest you get one of those too.
These are lithium-iron . . .
http://tinyurl.com/m4mlvsq
but for the purposes of my articles, it doesn't matter. If
the cells being offered by the various vendors take FMEA
into account and drive risks to acceptably low levels,
we have to assume that the energies contained are (1)
only allowed to get out through the terminals as electron
flow or (2) are very low risk due to management of manufacturing
quality and/or some manner of de-rating . . . like operating
them in the lower half of their energy storage tank?
My second point is: Could a simple solid state DC voltage regulator
be designed to bring the 16.8 V. down to 14.4 V? This would maximize
the potential of the lithium battery.
This is exactly what the makers of computers, tablets,
cell phones, and other products do. They use chargers
designed for the battery voltage selected . . . and discharge
to switch-mode power supplies that offers the desired system
voltage. Unfortunately, our 'charger' is that belt driven
thingy up front that is not especially tailored to the
care and feeding of lithium. Even if it were, then yes, we'd
need some mater of dc/dc converter to re-flavor the volts
to 14.4.
The thrust of my articles is to explore the cost/benefit
ratio for 'going lithium'. After you've spent the dollars
for the premium product, can you get off shorter runways,
fly over taller mountains, endure longer with a failed
alternator, or carry more baggage?
The design decisions are sort like those we should have
considered when we put those headers and 4-bbl carburetors on
our school transportation car . . . when we were so strapped
for cash that the used tire store was more likely to get
our business than Firestone. Good decision making is called
spontaneous organization, the science of elegant trade-offs.
I have read the AeroElectric Connection through a second time and
really appreciate the work you do.
Cheers!
Thank you for that endorsement. I'm pleased that you find
the work useful.
Bob . . .
Message 5
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| Subject: | Re: lithium facts |
Bob,
It seems to me that your question "can you get off shorter runways, fly
over taller mountains, endure longer with a failed alternator, or carry
more baggage?" adds little to the discussion. I say this because making an
airplane light is accomplished by many decisions to save small amounts of
weight by going with option B rather than option A, option D rather than
option C, etc. The cumulative result of all of these decisions does indeed
allow one to get off quicker, climb faster, carry more baggage, etc.
However, if we were to evaluate each decision individually, as you seek to
do with lithium batteries, probably none of them achieve a meaningful
difference in aircraft performance.
The question to ask is not what the effect will be on aircraft performance.
We already know that. This is no mystery. The question is already answered,
because every pound counts just as much as every other pound when it comes
to weight related performance whether it be a lighter battery, the choice
of titanium over stainless steel for the firewall, or the decision to go on
a diet to achieve a smaller beer belly. It seems to me the important
questions are "How does the cost of lithium compare to the cost of lead
acid?" and "How does the safety of lithium compare to the safety of lead
acid?" Those questions are important. Questions of weight related aircraft
performance are merely rhetorical.
On Sun, Nov 2, 2014 at 2:11 PM, Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> At 15:55 2014-11-02, you wrote:
> Hi Bob;
>
> I have heard, but have no personal experience, that the danger of fires
> from lithium iron batteries is much reduced in comparison to lithium ion
> batteries, while their weight is only slightly greater.
>
> To be sure, there are big differences in how the various
> chemistries behave AFTER the fire starts . . . but all
> battery chemistries from lead-acid to ni-cad, to lithium
> store a lot of energy in a relatively small volume. So
> all chemistries present some hazard for rapid release of that
> energy to varying degrees. Even the out-gassing products
> of Li-Iron are combustible. This is why the True Blue batteries
>
> [image: []]
>
>
> * . . . have those little 'smoke stacks' on top. They connect to a vent
> tube designed to take the nasties over-board in the event of catastrophic
> failure within a case DESIGNED to contain such events. To test the
> integrity of the case, the protective features of the battery management
> system (BMS) are disabled and the test lab puts 42 volts to the array of
> cells. After a period of time, a 'fog' of nasties begins to pour from the
> vent but case temperatures remain quite nominal . . . non-hazardous to
> children and other living things aboard the airplane. The design philosophy
> calls for getting this electronic version of nitro-glycerine packaged in a
> manner that contains worst-case failures . . . Damn I love FMEAs! Fooey on
> that reliability study stuff . . . assume the worst and tame it. *So one
> of my questions is: With which type of battery are you experimenting? If
> it's not lithium iron, I suggest you get one of those too.
>
> These are lithium-iron . . .
>
> http://tinyurl.com/m4mlvsq
>
> but for the purposes of my articles, it doesn't matter. If
> the cells being offered by the various vendors take FMEA
> into account and drive risks to acceptably low levels,
> we have to assume that the energies contained are (1)
> only allowed to get out through the terminals as electron
> flow or (2) are very low risk due to management of manufacturing
> quality and/or some manner of de-rating . . . like operating
> them in the lower half of their energy storage tank?
>
> My second point is: Could a simple solid state DC voltage regulator be
> designed to bring the 16.8 V. down to 14.4 V? This would maximize the
> potential of the lithium battery.
>
> This is exactly what the makers of computers, tablets,
> cell phones, and other products do. They use chargers
> designed for the battery voltage selected . . . and discharge
> to switch-mode power supplies that offers the desired system
> voltage. Unfortunately, our 'charger' is that belt driven
> thingy up front that is not especially tailored to the
> care and feeding of lithium. Even if it were, then yes, we'd
> need some mater of dc/dc converter to re-flavor the volts
> to 14.4.
>
> The thrust of my articles is to explore the cost/benefit
> ratio for 'going lithium'. After you've spent the dollars
> for the premium product, can you get off shorter runways,
> fly over taller mountains, endure longer with a failed
> alternator, or carry more baggage?
>
> The design decisions are sort like those we should have
> considered when we put those headers and 4-bbl carburetors on
> our school transportation car . . . when we were so strapped
> for cash that the used tire store was more likely to get
> our business than Firestone. Good decision making is called
> spontaneous organization, the science of elegant trade-offs.
>
>
> I have read the AeroElectric Connection through a second time and really
> appreciate the work you do.
> Cheers!
>
> Thank you for that endorsement. I'm pleased that you find
> the work useful.
>
> Bob . . .
>
> *
>
>
> *
>
>
Message 6
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| Subject: | Re: lithium facts |
Ken,
You missed one question: How does the performance of Li battery
technology compare to Pb with respect to maintaining our necessary
electronic equipment (aka electro-whizzies) until we can make a safe
return to terra firma. That was the area of greatest deficiency I found
when doing my brief evaluation.
Blue skies & tailwinds,
Bob Borger
Europa XS Tri, Rotax 914, Airmaster C/S Prop (75 hrs).
Little Toot Sport Biplane, Lycoming Thunderbolt AEIO-320 EXP
3705 Lynchburg Dr.
Corinth, TX 76208-5331
Cel: 817-992-1117
rlborger@mac.com
On Nov 2, 2014, at 6:04 PM, Ken Ryan <keninalaska@gmail.com> wrote:
Bob,
It seems to me that your question "can you get off shorter runways, fly
over taller mountains, endure longer with a failed alternator, or carry
more baggage?" adds little to the discussion. I say this because making
an airplane light is accomplished by many decisions to save small
amounts of weight by going with option B rather than option A, option D
rather than option C, etc. The cumulative result of all of these
decisions does indeed allow one to get off quicker, climb faster, carry
more baggage, etc. However, if we were to evaluate each decision
individually, as you seek to do with lithium batteries, probably none of
them achieve a meaningful difference in aircraft performance.
The question to ask is not what the effect will be on aircraft
performance. We already know that. This is no mystery. The question is
already answered, because every pound counts just as much as every other
pound when it comes to weight related performance whether it be a
lighter battery, the choice of titanium over stainless steel for the
firewall, or the decision to go on a diet to achieve a smaller beer
belly. It seems to me the important questions are "How does the cost of
lithium compare to the cost of lead acid?" and "How does the safety of
lithium compare to the safety of lead acid?" Those questions are
important. Questions of weight related aircraft performance are merely
rhetorical.
Message 7
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| Subject: | Re: lithium facts |
Yes, I should have included that. Also I should have included "How does Li
compare to Pb with respect to cranking the engine?"
On Sun, Nov 2, 2014 at 3:29 PM, Robert Borger <rlborger@mac.com> wrote:
> Ken,
>
> You missed one question: How does the performance of Li battery technology
> compare to Pb with respect to maintaining our necessary electronic
> equipment (aka electro-whizzies) until we can make a safe return to terra
> firma. That was the area of greatest deficiency I found when doing my
> brief evaluation.
>
> Blue skies & tailwinds,
> Bob Borger
> Europa XS Tri, Rotax 914, Airmaster C/S Prop (75 hrs).
> Little Toot Sport Biplane, Lycoming Thunderbolt AEIO-320 EXP
> 3705 Lynchburg Dr.
> Corinth, TX 76208-5331
> Cel: 817-992-1117
> rlborger@mac.com
>
> On Nov 2, 2014, at 6:04 PM, Ken Ryan <keninalaska@gmail.com> wrote:
>
> Bob,
>
> It seems to me that your question "can you get off shorter runways, fly
> over taller mountains, endure longer with a failed alternator, or carry
> more baggage?" adds little to the discussion. I say this because making
> an airplane light is accomplished by many decisions to save small amounts
> of weight by going with option B rather than option A, option D rather than
> option C, etc. The cumulative result of all of these decisions does indeed
> allow one to get off quicker, climb faster, carry more baggage, etc.
> However, if we were to evaluate each decision individually, as you seek to
> do with lithium batteries, probably none of them achieve a meaningful
> difference in aircraft performance.
>
> The question to ask is not what the effect will be on aircraft
> performance. We already know that. This is no mystery. The question is
> already answered, because every pound counts just as much as every other
> pound when it comes to weight related performance whether it be a lighter
> battery, the choice of titanium over stainless steel for the firewall, or
> the decision to go on a diet to achieve a smaller beer belly. It seems to
> me the important questions are "How does the cost of lithium compare to the
> cost of lead acid?" and "How does the safety of lithium compare to the
> safety of lead acid?" Those questions are important. Questions of weight
> related aircraft performance are merely rhetorical.
>
> *
>
>
> *
>
>
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