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mjpereira68(at)gmail.com
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 Posted: Sun Oct 09, 2011 4:48 pm Post subject: Lithium Batteries? |
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| Quote: | 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.
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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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Eric M. Jones
Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts
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| Posted: Tue Oct 11, 2011 4:15 pm Post subject: Re: Batteries? |
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A few years ago I related to Bob N. my experiences with a couple 12V carbon-zinc Eveready lantern batteries that I used to power a portable Telex intercom (which usually plugged into the rarely-connected cigar lighter in rented Cessnas). The first battery was found dead under mysterious circumstances (I was probably lucky). The replacement battery, upon shutting down the aircraft was too hot to touch and I grabbed it by the wires and tossed it out onto the asphalt. It melted a dent in the ramp. It was smoking.
I surmised that the batteries had some internal crushing damage from rapid descent, but perhaps they were damaged from voltage fed back from the intercom. But I can't see how. The intercom was undamaged.
This whole thing remains a mystery, but I offer it as a clue regarding batteries.
Batteries might need to have mechanics that withstand deformation by rapid pressure changes.
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_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net |
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Float Flyr
Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland
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| Posted: Fri Oct 14, 2011 6:24 pm Post subject: Lithium Batteries? |
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I've heard of much worse than this with a NiCad aircraft battery which
almost resulted in a Sikorsky S-92 being unceremoniously dumped off an oil
platform. Batteries are not always our friends.
Noel
--
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Noel Loveys
Kitfox III-A
Aerocet 1100 Floats |
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nuckolls.bob(at)aeroelect
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| Posted: Fri Oct 14, 2011 7:09 pm Post subject: Lithium Batteries? |
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At 09:20 PM 10/14/2011, you wrote:
| Quote: |
I've heard of much worse than this with a NiCad aircraft battery which
almost resulted in a Sikorsky S-92 being unceremoniously dumped off an oil
platform. Batteries are not always our friends.
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One could say the same thing about barrels
of gasoline, 400 h.p. engines in street machines,
or BD-5J airplanes.
When operated within their respective limits compatible
with the environment, they can seem quite benign
and spectacularly useful.
But in the wrong hands short of skill or knowledge,
they can prove quite hazardous. I was out on a field trip
with K. Razak many moons ago and had to slap out an
escalating source of smoke and bad smells from a pants
pocket. I'd tossed a handful of AA alkaline cells
into the pocket with a bunch of coins and a key-ring.
If those had been synthetic as opposed to good ol'
denim Dickies, I might still bear the "mark of Duracell"
on my thigh!
I did it in good company. Had lots of lawyers standing
around hoping we were going to do some good things
for them. I told them that hat-dance entertainment
was no extra charge. Now, if that had been a
lithium cell . . .
Bob . . .
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