Electrically Powered Ultralight Aircraft

At 22:48 13 August 2007, Bill Daniels wrote:

'Dana M. Hague' 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


Here is a link to an article about some new batteries,
Silver Zinc rechargeables, with 30% better energy density
than Lithium ions'. They are much less volatile and
much more eco-friendly, with 95% of the critical materials
able to be recovered, check it out.
http://www.gizmag.com/go/7743/

Paul Hanson
"Do the usual, unusually well"--Len Niemi

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 Aug 10, 3:14 pm, Martin Gregorie
wrote:
The only electric winch I've seen specs for, the ESW2B,http://www.startwinde.de/, solves that problem by consisting largely of
a bank of heavy duty 88 AH SLAs. These act as a buffer between the mains
supply and the winch motor, a 200 kW unit.

I know of a winch in Denmark which is diesel-electric. It sits on an
old Scania truck whose engine is connected to an alternator, and the
alternator to the winch motor, all under (reasonably simple) computer
control. It's self-contained, but gives smooth, powerful, controlled
and repeatable launches. IMO it's probably the best winch design from
a technical stand point. However it's much more expensive than a
normal big V8/truck axle winch, and it's not clear that the benefits
outweigh the costs.


Dan

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

In rec.aviation.piloting Charles Vincent wrote:
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.

Well, that's true enough, but the above was about hybrid cars.

--
Jim Pennino

Remove .spam.sux to reply.

wrote:

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.


Well, that's true enough, but the above was about hybrid cars.



No, it's not true enough.

To carry more weight at the same speed and altitude requires more LIFT.

A higher CL - and/or more wing area.

THEN, to overcome the increased drag, THEN you need more power.

But more power by itself won't satisfy the constraints...

wrote:
In rec.aviation.piloting Charles Vincent wrote:
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.

Well, that's true enough, but the above was about hybrid cars.


Well in cruise in a car, more weight does not increase your aerodynamic
drag like it does on an airplane, but it does increase your rolling
resistance in the real world, so there is no free lunch. Different
tradeoffs for different missions. I guess that is why cheetahs and
sparrows look so different.

Charles

In rec.aviation.piloting cavelamb himself wrote:
wrote:

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.


Well, that's true enough, but the above was about hybrid cars.



No, it's not true enough.

To carry more weight at the same speed and altitude requires more LIFT.

A higher CL - and/or more wing area.

THEN, to overcome the increased drag, THEN you need more power.

But more power by itself won't satisfy the constraints...

So if I add 1 pound to a 2400 pound gross aircraft loaded to 2300 pounds,
it would be impossible to cruise at the same speed and altitude without
the 1 pound unless I added wing area?

How about 50 pounds?

--
Jim Pennino

Remove .spam.sux to reply.

In rec.aviation.piloting Charles Vincent wrote:
wrote:
In rec.aviation.piloting Charles Vincent wrote:
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.

Well, that's true enough, but the above was about hybrid cars.


Well in cruise in a car, more weight does not increase your aerodynamic
drag like it does on an airplane, but it does increase your rolling
resistance in the real world, so there is no free lunch. Different
tradeoffs for different missions. I guess that is why cheetahs and
sparrows look so different.

Unless the added weight is enough to deform the tires, the increase
in rolling resistance in the total energy expediture can't be found.

--
Jim Pennino

Remove .spam.sux to reply.