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Once completed there will ultimately be little to externally distinguish the Whisper™ 3G from its previous version. Changes in the e-Traction® System will include the more powerful SM500/3FE wheel hub units for a greater range of missions, a redesigned Universal Rear Axle to compensate for the greater depth of the wheel hub systems, more powerful U27 XP Lithium-ion batteries for greater storage and higher instant on demand energy availability, and doubling the output of the generator section of the Auxiliary Power Unit using the more powerful SM350/2AL direct-drive system.
Rationale for increased torque: A larger amount of available torque should not measurably alter the energy efficiency of the vehicle (all else being equal), but it does make it possible to overcome heretofore insurmountable obstacles. The Whisper has performed very well in the Netherlands, which happens to be fairly flat. With the planned changes, a prolonged or steep hill climb, such as the famed Route 42 in Stuttgart, should now become feasible in each driving scenario. The "sacrifice" of increased torque is the higher unit cost of the direct-drive system, a slight weight penalty and a minor loss of interior space. It is important to note that an electric direct-drive system's energy consumption is governed by the vehicle's rolling- and air-resistance, the terrain characteristics and the driving style of the operator. Only the added weight of the more potent e-Traction® System, estimated at about 5% of the empty weight, is the only variable directly attributable to the energy consumption variable (all else being equal). The improved acceleration and obstacle climbing ability, however, may actually off-set some of the anticipated efficiency reduction. Rationale for increased energy storage: The Lithium-ion battery storage functions as the buffer between supply and demand both in the traction (acceleration) mode and during (braking) regeneration. Bigger is also in this case better. The newly developed U27 XP batteries from Valence Technologies offer possibilities that had previously not been available in the size, weight and prices currently being offered. The improved performance of these batteries, with their also improved CANopen Battery Management System, are now being offered at a substantially lower cost per kW than experienced 2½ years ago when the initial Lithium-ion batteries were installed in the Whisper™ and the e-Traction-Bus. Rationale for increased energy generation capability: The SM350/1AL generator in the APU of the Whisper™, in its Dutch city-bus only configuration, produced an adequate maximum of 32 kW. As was demonstrated in highway tests, it required about 57 kW at a speed of 80 km/h, when air-resistance becomes an exponentially increasing factor. The energy generation supply shortfall for this city-bus configuration had to be drawn from the batteries. At the time, this deliberately considered "deficit spending" scheme seemed quite workable for a city-bus, which after all would rarely ever be operated at such high speeds. Typically a city-bus averages between 15 and 20 km/h. This arrangement, therefore, allowed for limited periods at top speed as the batteries could otherwise become too severely drained. To create greater operational flexibility, it has been decided to sacrifice a small amount in energy efficiency in exchange for the ability to rival with conventional buses on just about any level. The newly developed SM350/2AL generator, producing twice the amount of energy (all else being equal) is expected to completely eliminate this operational limitation. This new configuration is not only more potent but also more costly in terms of components, weight, space requirement and probably fuel consumption. A more powerful diesel engine will also be required. Tests will ultimately show to what extent energy efficiency will have been influenced by this new arrangement, but the impact is assumed to be minimal as a result of the variable speed/output brushless DC generator, which produces the exact amount of energy needed for any given phase of operation. When the batteries are sufficiently charged, after a brief trickle charge period, the CANopen e-Traction® Energy Management System will simply shut down the ICE (internal combustion engine). |
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