Li-ion batteries lift novel sailplane to new altitudes
A switch from Ni-MH batteries makes all the difference for this novel
electrically powered glider
The Antares self-launching sailplane has been hailed by its German
manufacturer, Lange Flugzeugbau, as the 'motorglider' of the future,
thanks to its almost silent and environmentally friendly propulsion
system. This comprises a brushless 42kW electric motor with external
rotor, power electronics, rechargeable batteries and a slowly revolving,
2m diameter 'pusher' propeller. During take-off and powered flight, the
motor/propeller unit is extended above the wing, but when soaring, all
this is retracted into the fuselage to maximise aerodynamic efficiency.
The prototype sailplane was powered by nickel metal hydride (Ni-MH)
batteries, which enabled it to reach an altitude of 1,890m. However,
hungry for even better performance, the design team decided to try
lithium-ion (Li-ion) batteries, which provide a high power capacity in a
lighter package (30% less heavy than the Ni-MH cells). The batteries
chosen were Saft's VL Li-ion cells, originally developed for hybrid and
electric vehicle applications. VL cells have a nominal capacity of 39Ah
and nominal voltage of 3.6V.
The complete Antares battery system is made up of 72 VL cells in series,
providing a nominal voltage of 260V. Its total weight is around 76kg -
some 13% of the sailplane's maximum all-up weight of 600kg, and it has
enough capacity (around 13 minutes at maximum power) to take Antares to
an altitude in excess of 3,000m. Even in the absence of thermals, this
provides up to one hour and forty minutes of flight before landing.
There's more information about Antares at www.lange.flugzeugbau.com