High capacity coupled with low weight make lithium-ion cells the ideal
solution to the power requirements of a new surface/underwater personal
propulsion system developed in Germany
The Delfjet electric jet-propelled water scooter was developed in Germany
by Jurgen Grimmeisen. The prototype was initially fitted with
nickel-cadmium batteries, but the design team decided that if the project
was to be commercially viable, the power source had to provide greater
capacity and weigh considerably less. The solution was to fit
rechargeable High Energy (HE) lithium-ion cells, originally designed by
Saft Industrial Battery Group to power electric vehicles. These batteries
provide twice the capacity and weigh two-thirds less than their
nickel-cadmium counterparts.
The Saft cells have a nominal capacity of 43Ah at 3.6V, enabling a 42V
battery to be constructed using just twelve cells in series with a total
weight of 12kg. By comparison, the nickel-cadmium equivalent has a
capacity of 25Ah and weighs 35kg (the Delfjet without batteries weighs
just 16kg). The batteries are housed in a water-tight compartment within
a removable nose-cone; they power a brushless 42V motor driving an
impellor. Charging takes just two hours and both charge and discharge
voltages are electronically monitored. With a capacity of 1,000
charge/discharge cycles, in this application the HE batteries are
expected to last more than 18 years. You can see a video clip of the
Delfjet in action by visiting www.delfsport.de