Electrically Powered Ultralight Aircraft

Please keep in mind that there are many lithium ion and lithium polymer
chemstries. It isn't too informative to just say "Lithium Polymer" or
Lithium Ion" without stating the precise chemistry. Further, chemistries
are changing almost daily. Many are proprietary. There's no such thing as
a "standard" lithium battery chemistry.

Valence, Saft and A123 Systems use chemistries that are far safer than the
relatively inexpensive Korean made model airplane batteries - safer than the
typical laptop or cell phone battery which are spec'd mainly on price.

Interestingly, the safest chemistries in the latest cells also offer faster
charging, greater energy density and will endure a FAR greater number of
charge cycles. They're also potentially cheaper.

I've already made a cell holder for A123 Systems "A1" cells. That's the
lithium phosphate nano cathode one used in 36V DeWalt power tools. You can
buy a couple of new DeWalt 36V power packs for $50 or so on Ebay. Then,
dismantle the pack to retrieve the individual cells. My pack will be 13.8
volts and 11AH weighing 3 pounds. It will be the same size as a 7AH 12V SLA
but weigh less than half as much.

Bill Daniels

Some Lithium cells can suffer thermal runaway and fire. Others are
extremely
wrote in message
oups.com...
On Aug 10, 5:12 pm, Dave wrote:
Are

you able to provide links to any forums or web sites related to this

Check this out:http://www.calcars.org/news-archive.html

David Johnson

Lithium Polymer batteries are widely used in RC planes, cars, etc and
are known to be potentially dangerous. Most runaway fires occur during
charging but it has also occurred to a lessor degree during discharge
and even storage. Vented charging safety bags are recommended for this
reason. There is a video on this link that shows the explosive power
of small LiPo's. Consider the size differance of these batteries to
the one hung under the trike in one of the first posts or those that
could be installed in the wings of a sailplane.
http://www.liposack.com/video.html

On Fri, 10 Aug 2007 17:12:09 GMT, Larry Dighera
wrote:

It sounds like you have quite a bit of experience in this area. Are
you able to provide links to any forums or web sites related to this
topic?

Try http://electricppg.com

I've been flying PPG for about 6 years now; got into it when I
realized I couldn't afford to restore my Taylorcraft. Finally managed
to get another plane (Kolb this time), but PPG is so much fun I don't
intend to give it up.

Never flew an electric PPG, though... they're still pretty rare birds.

-Dana
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On Sat, 11 Aug 2007 15:35:25 GMT, Larry Dighera
wrote:

I would assume that the source of these Li-ion Polymer battery fires
is excessive electrical current flowing through the battery either
from too high a charging rate, too high a discharge rate, or a short
internal (as in the case of the Sony laptop cells) or external, or
being over charged. Perhaps it would be prudent to install a circuit
breaker of fuse to prevent too high a current and a timer to
disconnect a forgotten charger.

I imagine the root of the problem is very low internal resistance
which, while making them very efficient, also allows the current to
"run away". Good circuit design can alleviate many of the issues, but
safety if the batteries are damaged in a crash is still an issue.

-Dana
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If replying by email, please make the obvious changes.
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"Dana M. Hague" d(dash)m(dash)hague(at)comcast(dot)net wrote in message
...
On Sat, 11 Aug 2007 15:35:25 GMT, Larry Dighera
wrote:

I would assume that the source of these Li-ion Polymer battery fires
is excessive electrical current flowing through the battery either
from too high a charging rate, too high a discharge rate, or a short
internal (as in the case of the Sony laptop cells) or external, or
being over charged. Perhaps it would be prudent to install a circuit
breaker of fuse to prevent too high a current and a timer to
disconnect a forgotten charger.

I imagine the root of the problem is very low internal resistance
which, while making them very efficient, also allows the current to
"run away". Good circuit design can alleviate many of the issues, but
safety if the batteries are damaged in a crash is still an issue.

-Dana
--

Any battery chemistry, including lead-acid, can overheat with excess
charging current - usually to the detriment of the battery and whatever it
is in at the time. All can do damage if they are shorted. The problem with
the first generation lithium cells was the chemistry released oxygen when
overheated which combined with the flammable lithium made an incendiary
bomb.

The newest lithium-nanophosphate cells do not release oxygen and thus do not
burn or explode although they can be damaged by overcharging. Cells made by
A123 Systems, Saft, Valence and others are more than safe enough for use in
aircraft or cars. They have a little less energy capacity than the old
chemistry but they make up for it with fast charging and long life. They
can typically manage a 20C discharge rate without harm - that's 200 amps for
a 10 AH battery. Admittedly, you don't want to short that.

Bill Daniels

On Mon, 13 Aug 2007 17:39:44 -0400, Dana M. Hague
d(dash)m(dash)hague(at)comcast(dot)net wrote in
:

safety if the batteries are damaged in a crash is still an issue.

I would think the hazard somewhat less than gasoline.

Larry Dighera wrote:
On Mon, 13 Aug 2007 17:39:44 -0400, Dana M. Hague
d(dash)m(dash)hague(at)comcast(dot)net wrote in
:

safety if the batteries are damaged in a crash is still an issue.

I would think the hazard somewhat less than gasoline.

The battery can produce it's own ignition source.

On Tue, 14 Aug 2007 08:40:29 -0500, "Gig 601XL Builder"
wrDOTgiaconaATsuddenlink.net wrote in
:

Larry Dighera wrote:
On Mon, 13 Aug 2007 17:39:44 -0400, Dana M. Hague
d(dash)m(dash)hague(at)comcast(dot)net wrote in
:

safety if the batteries are damaged in a crash is still an issue.

I would think the hazard somewhat less than gasoline.

The battery can produce it's own ignition source.


You have a point. While a source of ignition (sparking wires, hot
muffler?) is required to ignite post-crash gasoline fumes, it would
take an un-fused short circuit or significant deformation of a battery
to potentially ignite a lithium battery. Granted, if the crash occurs
as a result of fuel exhaustion, there is little fire hazard, while the
lithium would always be aboard.

Larry Dighera wrote:
On Tue, 14 Aug 2007 08:40:29 -0500, "Gig 601XL Builder"
wrDOTgiaconaATsuddenlink.net wrote in
:

Larry Dighera wrote:
On Mon, 13 Aug 2007 17:39:44 -0400, Dana M. Hague
d(dash)m(dash)hague(at)comcast(dot)net wrote in
:

safety if the batteries are damaged in a crash is still an issue.
I would think the hazard somewhat less than gasoline.
The battery can produce it's own ignition source.


You have a point. While a source of ignition (sparking wires, hot
muffler?) is required to ignite post-crash gasoline fumes, it would
take an un-fused short circuit or significant deformation of a battery
to potentially ignite a lithium battery. Granted, if the crash occurs
as a result of fuel exhaustion, there is little fire hazard, while the
lithium would always be aboard.


How much of a fire hazard would a paper battery be?

http://www.energy-daily.com/reports/...per _999.html

On Wed, 15 Aug 2007 12:23:00 GMT, CanalBuilder
wrote in
:

How much of a fire hazard would a paper battery be?

http://www.energy-daily.com/reports/...per _999.html

That is an interesting device indeed. Given these quotes from the
article:

Rensselaer researchers infused this paper with aligned carbon
nanotubes, which give the device its black color. The nanotubes
act as electrodes and allow the storage devices to conduct
electricity. The device, engineered to function as both a
lithium-ion battery and a supercapacitor, can provide the long,
steady power output comparable to a conventional battery, as well
as a supercapacitor's quick burst of high energy. ...

Along with use in small handheld electronics, the paper batteries'
light weight could make them ideal for use in automobiles,
aircraft, and even boats. The paper also could be molded into
different shapes, such as a car door, which would enable important
new engineering innovations.

"Plus, because of the high paper content and lack of toxic
chemicals, it's environmentally safe," Shaijumon said. ...

"Plus, because of the high paper content and lack of toxic
chemicals, it's environmentally safe," Shaijumon said.

"It's a way to power a small device such as a pacemaker without
introducing any harsh chemicals - such as the kind that are
typically found in batteries - into the body," Pushparaj said.

I find the article to be somewhat contradictory in its characterizing
a lithium-ion battery as containing no harsh chemicals. And its claim
of using carbon electrodes in a supercapacitor seem very
counterintuitive for a low impedance device. It reads like an April
Fools Day hoax.

wrote:
In rec.aviation.piloting Tim Ward wrote:

wrote in message
...

The advantage from the electric engine at cruise is that it uses zero
energy.

Snippage
--
Jim Pennino

Remove .spam.sux to reply.

You want to support this, somehow?

Tim Ward

At cruise the electric motor is turned off.

The only energy used is some slight bearing friction.

The electric motor is only turned on when more power than the gas
engine can provide is needed.


To carry more weight at the same speed and altitude takes more power, so
you have to account for the energy expended kiting you deadweight
electric takeoff system around the sky as well. Sizing an engine for
cruise has been done, if only backwards. Think JATO. Most JATO's are
actually RATO (rocket assisted takeoff). I expect RATO would beat an
electric system based on energy density and the fact that when it is
done you have reduced your weight by the fuel. I also suspect for a
given amount of thrust the rocket will be lighter than an electric motor
and associated clutches and gearing. In my opinion, at this point in
time it is just as practical for a homebuilt as well as in not.


Charles