On Thu, 21 Apr 2016 08:18:53 -0600, Dan Marotta wrote:

Putting range extender on glider is a good idea. They are being made
everywhere for electric cars and should be affordable (when mass
produced). Surprising that the weight of pod is 100kg. That's one big
range extender. No wonder they couldn't fit it in the fuselage.

Not that surprising: the energy density of LiPoly/Li-ion batteries is low
by comparison with avgas.

A quick look round Wikipedia gives a figure of 0.1-0.25Kw/kg for Li-ion
batteries and 33.3kw/US gal. Since a US gallon of gas weighs 6.073 lbs
and there are 2.2 lbs to a kilogram, that gives 12Kw/kg for gasoline.
IOW on their figures gasoline has at least 48 times the energy density of
Li-ion batteries.

Now you know why the long range S-class Tesla totes 540kg of battery,
while a full tank in my Focus weighs around 50kg - (55 litres of petrol +
guessed 5kg of steel). Both have a similar driving range +/- 20%.


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martin@ | Martin Gregorie
gregorie. | Essex, UK
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