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.