Can Aircraft Be Far Behind?

On Wed, 10 Jan 2007 15:39:17 -0000, Dylan Smith
wrote in
:

On 2007-01-09, Larry Dighera wrote:
Charge time for the Altair batteries is only a few minutes as I
recall.

I'm extremely skeptical - if these batteries are not snake oil, consider
this. Let's call "a few minutes" 10 minutes, and let's say the battery
pack stores 70kWh (enough to run a motor producing 94 hp for 1 hour).

To put 70kWh's worth into a battery pack in 10 minutes would require a
charger capable of putting out 420kW.

At 120 volts, 420kW would require a current of 3500 amps. Look at the
massive thick wire coming into your house (which maybe is rated at 80
amps).

Now let's say these batteries give three hours worth at 70kWh, and
charge in 10 minutes - now you're up to 10,500 amps at 120 volts. YOU
CANNOT AVOID high voltage, high amperage controls in a vehicle like the
Tesla, regardless of the battery technology. You are moving around
tremendous amounts of current. If this mythical charger was 99%
efficient, the 1% emitted as heat could heat an entire office building
in the dead of winter in central Canada. To consider this new battery
technology a silver bullet is to ignore the well established laws of
physics. Now imagine if *everyone* is charging their mythical car. No
practicable electricity distribution network that's feasable in the near
term could cope.

It would be totally and utterly impractical to charge these batteries at
this rate. I'll let you do the calculations for the equivalent in
electricity that filling a Cessna 150 with avgas in 4 minutes (the
typical time to do it at a self serve pump) would be.


The issue of high charging current is true, of course.

After studying the information available on the Altair web site
http://www.altairnano.com/markets_amps.html, it has become apparent
that their battery technology trades energy density for low internal
resistance. So their product is probably not the best choice for
aircraft due to weight considerations.

Recently, Larry Dighera posted:

On Wed, 10 Jan 2007 15:39:17 -0000, Dylan Smith

It would be totally and utterly impractical to charge these
batteries at this rate. I'll let you do the calculations for the
equivalent in electricity that filling a Cessna 150 with avgas in 4
minutes (the typical time to do it at a self serve pump) would be.

The issue of high charging current is true, of course.

After studying the information available on the Altair web site
http://www.altairnano.com/markets_amps.html, it has become apparent
that their battery technology trades energy density for low internal
resistance. So their product is probably not the best choice for
aircraft due to weight considerations.

According to their W/kg chart, their batteries trade a lower specific
energy (W hr/kg) for a considerably higher specific power, but I would
think that Altair's operating temperature range would be a more important
factor w/r/t aviation, as the other batteries' performance suffers badly
in low-temperature environments. I doubt that a typical Li-ion battery
would deliver the indicated specific energy in aviation temperatures, so
any weight benefit would be compromised.

Neil

On Mon, 15 Jan 2007 14:31:16 GMT, "Neil Gould"
wrote in
:

Recently, Larry Dighera posted:

On Wed, 10 Jan 2007 15:39:17 -0000, Dylan Smith

It would be totally and utterly impractical to charge these
batteries at this rate. I'll let you do the calculations for the
equivalent in electricity that filling a Cessna 150 with avgas in 4
minutes (the typical time to do it at a self serve pump) would be.

The issue of high charging current is true, of course.

After studying the information available on the Altair web site
http://www.altairnano.com/markets_amps.html, it has become apparent
that their battery technology trades energy density for low internal
resistance. So their product is probably not the best choice for
aircraft due to weight considerations.

According to their W/kg chart, their batteries trade a lower specific
energy (W hr/kg) for a considerably higher specific power, but I would
think that Altair's operating temperature range would be a more important
factor w/r/t aviation, as the other batteries' performance suffers badly
in low-temperature environments. I doubt that a typical Li-ion battery
would deliver the indicated specific energy in aviation temperatures, so
any weight benefit would be compromised.

Battery temperature is important. However it's important to realize
that batteries with a higher internal resistance will generate more
heat under load than those with lower internal resistance, so I doubt
low temperature would be an issue with conventional LiIon batteries.
In fact, the Tesla car needs a liquid cooling system to remove battery
heat, and I would suspect that some sort of cooling system would be
required for aviation applications also.

If it is the weight of the batteries that preclude the use of electric
power for airplane use, using the Altair batteries, with half the
energy density of conventional LiIon cells, wouldn't make very good
sense. The A123Systems M1 cells, with their claimed "the highest
commercially available power density of any Li Ion chemistry" may be
an enabling technology for electrically powered airplanes:
http://www.a123systems.com/html/home.html

Larry Dighera wrote:

If it is the weight of the batteries that preclude the use of electric
power for airplane use, using the Altair batteries, with half the
energy density of conventional LiIon cells, wouldn't make very good
sense. The A123Systems M1 cells, with their claimed "the highest
commercially available power density of any Li Ion chemistry" may be
an enabling technology for electrically powered airplanes:
http://www.a123systems.com/html/home.html

Power density isn't the issue. That only means they can dump the energy
contained in the battery faster than other types. Their batteries would be
useful where you need high power for short bursts of time, like hand-held
drills, or photo flash units. Power density says nothing about how much
energy is contained in the battery.

The important measure for aircraft application is energy density. The A123
batteries have about 1/2 the energy density of current LiIon batteries,
which means you would need a battery that weighed twice as much as other
types of LiIon batteries. This is moving the wrong way, if they are to be
practical in aircraft application.