"Scott" wrote in message
...
Richard Riley wrote:

On Jun 16, 7:37 pm, Larry Dighera wrote:

How Beat The High Cost Of Fuel

The motor is powered by a 78 pound, custom-built lithium-ion polymer
battery with a power output of "5.6 kilowatt hours"; projected life is
300 to 500 full discharge cycles or more than 1,000 partial cycles.
The battery can be recharged in as little as two hours using a
220-volt charger (or six hours with a 110-volt charger). The cost for
a full recharge is 70 cents with the 110-volt charger. Fishman says
it's feasible to carry a small 110-volt charger as baggage on
cross-country flights.


1 horsepower = .75kw. So 5.6 kilowatt hours is only 7.51 horsepower
hours. Good enough for a short burst to get you to altitude and soar
the thermals, bu you aren't going anywhere cross country.

Compare it to a really inefficient 2 stroke, burning .6 lb/hp-hr.
Your battery is equal to .75 gallons of gas.

Wait a second...5.6 KWH doesn't really tell you how much HP it is, does
it? All it says is that it consumes 5.6KW in an hour. If you only ran
the motor for 5 minutes per hours, the HP would be 12 times that or
approx. 90 HP. Using KW HOURS doesn't tell the whole story. Running a
100W light bulb 10 hours uses 1 KWH and so does running a 500W bulb for 2
hours but the 500W bulb does more work at any instant in time (it's a lot
brighter!). Now, if that motor was rated at 5.6KW, then yes, I'd agree it
is about 7.5 HP.

Scott

You have a good point, but the KW Hours rating of the battery does seem a
bit low. Even when you consider that cooling drag nearly absent, what
little I think I know about the base airframe suggests that the battery
rating needs to be at least twice the stated amount in order to provide the
stated performance and endurance. The usual power of ten error in
transcription does not make much sense in this case, but there are
apparently two batteries of equal sive--and everything that I could find
appeared to originate from a single article.

In any case, it is interesting; but the economics really do not work based
upon the stated maximum10 year and 1000 hour battery battery life. Even if
the electricity was free and gasolene was more than twice its current cost,
the gasolene powered airplane, on which it is bsed, would still give much
greated utility for less cost. Nontheless, my hat's off to him for the
effort.

Peter