Today's Message Index:
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1. 12:25 AM - Re: AeroElectric-List Digest: 2 Msgs - 10/08/11 (K Fohringer)
2. 07:12 AM - Re: Electric aircraft issues (Glen Matejcek)
3. 07:59 AM - Re: Re: Electric aircraft issues (Robert L. Nuckolls, III)
4. 10:28 AM - Re: Electric aircraft issues (Jim Berry)
5. 01:40 PM - Re: Electric aircraft issues (rparigoris)
6. 03:06 PM - Re: Re: Electric aircraft issues (Charlie England)
7. 05:48 PM - Re: Lithium Batteries? (Michael Pereira)
Message 1
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| Subject: | RE: AeroElectric-List Digest: 2 Msgs - 10/08/11 |
Message 2
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| Subject: | Re: Electric aircraft issues |
Right off the top of my head, I can think of 3 freighter losses linked to Li batteries.
One got on the ground and burned on the runway for about 4 hours, without
loss of life. The other two didn't end so well. In all cases, the batteries
were palletized for shipping, not even part of an active circuit. You can
also google a video of a laptop sitting on the floor at LAX, and watch it erupt.
It's pretty spectacular.
FWIW, at least one of the planes in my past was configured with the NiCads outside
the primary structure. Absolute worst case, a runaway battery could exit
the bottom of the composite blister without doing more grievous harm. I don't
think it would have even depressurized the plane.
Something to consider-
Glen Matejcek
Message 3
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| Subject: | Re: Electric aircraft issues |
>
>
>FWIW, at least one of the planes in my past was configured with the
>NiCads outside the primary structure. Absolute worst case, a
>runaway battery could exit the bottom of the composite blister
>without doing more grievous harm. I don't think it would have even
>depressurized the plane.
Which speaks to the evolution of a technology . . .
I recall working a MU2 accident down in TX that
involved a ni-cad battery fire . . . that would
have been in the 70's. We eventually learned how
to live amicably with that technology's worst
traits. Unfortunately, some of the lessons came
with very high costs.
I've not done a detailed study of incidents but
I sense a trend suggesting that the lithium
cells are particularly vulnerable to mischief when
allowed to deeply discharge and are then recharged
with the systems normal power source that is also
capable of running the whole system.
The Shorai folks caution against an energetic
recharge of a deeply depleted battery. The task
of bringing up a dead battery is best accomplished
by their proprietary charger/cell-balancing product.
I wonder if the laptop fire at LAX wasn't produced
in a computer being recharged by a pax during a
stop between planes. Batteries on airplanes tend
to be deeply discharged more often than not . . .
and then the pax hopes to get 'er charged back
up between flights.
So it seems likely that if one chooses to use
the Shorai (or any other product) for an
airplane, it is most likely to perform as advertised
for a cranking battery where the alternator picks
up system loads and replenishes a few percent of
discharge each flight cycle.
If one DOES experience an alternator failure,
then by all means, use what ever energy the battery
contains in carrying out plan-B. Upon reaching the
ground, remove the battery from the airplane for
specialized recharging in a less-risky environment.
The Cessna ramp fire probably involved a disorderly
recharge of a badly depleted battery.
Bob . . .
Message 4
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| Subject: | Re: Electric aircraft issues |
Bill Dube, who used to post to this site re his LED lights, probably has as much experience as anyone with the A123 batteries. He uses them in his battery powered dragster motorcycle (www.killacycle.com) and Bonneville racer. Search the archives for his take on using & charging these batts.
Jim Berry
RV-10
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=354448#354448
Message 5
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| Subject: | Re: Electric aircraft issues |
Hi Bob
You mentioned:
"The Shorai folks caution against an energetic
recharge of a deeply depleted battery."
This is not only true of a Lithium battery, but charging a discharged lead acid
battery with a high powered alternator that's trying to maintain a constant voltage
(just got aeroplane or car running from a jump start) is not very easy
on the battery.
How could one limit the charging amps going into the battery yet still allow the
alternator to carry any loads?
Ron P.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=354459#354459
Message 6
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| Subject: | Re: Electric aircraft issues |
On 10/09/2011 03:36 PM, rparigoris wrote:
> --> AeroElectric-List message posted by: "rparigoris"<rparigor@suffolk.lib.ny.us>
>
> Hi Bob
>
> You mentioned:
> "The Shorai folks caution against an energetic
> recharge of a deeply depleted battery."
> This is not only true of a Lithium battery, but charging a discharged lead acid
battery with a high powered alternator that's trying to maintain a constant
voltage (just got aeroplane or car running from a jump start) is not very easy
on the battery.
> How could one limit the charging amps going into the battery yet still allow
the alternator to carry any loads?
> Ron P.
>
That was my 1st reaction, as well. Achieving it should be as simple (not
to be confused with cheap...) as the alternator feeding a switching
power supply which feeds only the custom charging circuit for the battery.
Charlie
Message 7
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| Subject: | Re: Lithium Batteries? |
> I was wondering if you had any thoughts on the use of lithium batteries in
> OBAM aircraft. ( http://www.lithiumaviationbattery.com/)
>
> (We're starting to see a lot of certification efforts for them around
> Wichita, Albuquerque, Savannah, other places on the east coast...)
>
> I've not had any conversation with the lithium battery
> program manager at HBC in a couple of years. I'll
> drop him a note and see if there's anything close to
> getting onto a type certificate.
>
> This is one area where the OBAM aircraft owner
> is justified in a wait-and-see response. It
> isn't like you can't go flying without a lithium
> battery. The ARE more expensive. They have fragilities
> and performance issues that may make their price
> difference still more unattractive. It would be
> useful to have some first-hand feedback from users.
>
> While the weight savings is compelling, they are
> not a drop-in replacement for RG in every respect.
> But if you're willing to be one of those users
> eager to share you own first-hand experiences,
> go for it.
Before even considering a lithium battery in a man carrying aircraft.
Please search for "lipo fire" on you-tube for examples of what *small*
r/c airplane lithium batteries are capable of doing when abused (by
physical damage or over charging). Granted, the A123 battery
chemistry is far more tolerant of abuse but not nearly to the extent
of a lead acid battery.
Also, any lithium battery technology is going to require some form of
electronic balancing controller if it's placed in a system capable of
recharging it. Ie. low voltage micro controllers monitoring the
charge and discharge current of the battery as a whole, and voltage
level of each cell. For anything off the self IC that you can buy the
standard way of handling one of these out of spec conditions is to
disconnect the battery from the load (or charge). Every laptop battery
you've owned has one of these buried inside it's significantly strong
plastic casing (the controller to keep the battery safe from
electronic abuse, the casing to keep it safe from physical abuse).
Still, you can find videos of laptops ablaze on you tube, which always
seem to get more exciting when the people in the video start tossing
glasses of water on the laptop in an attempt to put it out. (Am I the
last person that took high school chemistry ?)
In my opinion, for a battery that's basically there to crank an
engine, level out the load on an alternator, and in an emergency
provide reserve power, it just isn't worth it. You're better off
placing one of the 8amp b&c gear driven backup alternators and then
saving weight by installing a battery just adequate to crank the
engine with a very short reserve time (ie, get the plane on the ground
after a double alternator failure, not fly out the tank).
For a electrically launched glider where all the charging is done at
the ground without time pressure I guess it's workable (in fact, it's
available from at least one production glider company). It's about
the only system that I can think of that would make me feel more
unsafe than sitting next to a tank of gasoline.
c'ya,
Michael
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