19 cost–benefit perspective, makes great sense. If you were producing a conventional vehicle, that type of solution would give you a 5–10% fuel economy improvement for a relatively modest on-cost. So why wouldn’t you? “On EVs, there are still range limitations, particularly where there is limited infrastructure and accessibility to charging points isn’t guaranteed, and I think that even with established EV infrastructure, there will be occasions – around busy events – where there are going to be pinch points. “Range extenders can help that; it’s just a simple difference in thinking. A hybrid is an ICE vehicle with electrification to make it more efficient, but as you get toward the plug-in hybrid end, you start defining which system dominates and you can look more to drive the car electrically. Then, in the case of the range extender, it is just an EV with a generator.” Improving electrification efficiency Ultimately, however, the efficiency of electrification and the need for emissions elimination means hybridisation, and range extenders are merely means to an end. When it comes to the future of private transportation, the challenge now is to determine those areas of the powertrain that offer the biggest opportunity for improvements in range and performance. “I think there’s most scope with the battery,” offers Bassett. “Typical motor efficiencies are already 95% and upwards, and while there are improvements to be found in wholevehicle efficiency, these are only fractional gains because generally modern vehicle drive systems are already quite efficient and we are now nibbling at the edges. “The trend for bigger SUVs creates aerodynamic drag and also adds vehicle mass, which increase rolling resistance and directly determine how much energy is required to accelerate the vehicle. When it comes to optimising vehicles, it is all about minimising parasitic power consumption from things like ECUs, pumps or fans that consume power, and maximising regeneration. “Braking regeneration is already pretty efficient, but wheel motors are quite an interesting technology because they offer packaging advantages but they are quite challenging from a torque delivery perspective. You don’t have any gear ratio between the motor and the wheel, so there will definitely be some developments in motor topology. “Ultimately, though, the battery is still a large, heavy and expensive part of the vehicle, so there is lots of opportunity for improvement. There are big strides being made in this area, but there are still questions around recycling and how efficiently we can recover the materials out of the battery at end of life. That’s really challenging at the moment. “I think with some cell technologies, fast charging will also see a big advancement, but the bigger the vehicle, the harder it becomes. Charging in seconds could be realistic for scooters, mopeds, power tools, those kinds of things, but once we get to trucks and buses it becomes more and more challenging due to the power levels involved to recharge large packs quickly.” The resource question around the use of batteries as a long-term solution remains a big question for Bassett. His efforts are clearly focused on a desire to reduce emissions across the board, using whatever means available – and there is now an ever-increasing range of options on the table. Bassett sees a place for many different propulsion technologies in the vehicles of the future and his work at MAHLE Powertrain continues to explore all avenues. “We have to be open to these different technologies and assess them all in an even way,” he concludes. “We shouldn’t overlook any opportunities to reduce environmental impact. “Renewable fuels and electricity are both mechanisms for transporting energy, but with renewable fuel, there’s a whole conversion chain and losses there. So, if you are using a renewable fuel, why wouldn’t you hybridise as well? There is also a space for fuel cells and hydrogen ICEs in cases where the amount of energy and the duty cycle just don’t fit. “Several companies are looking at hydrogen for the off-highway heavy duty sector, for example, and I think we will also see that for machines like combine harvesters, which are used intensively in a remote location for a few weeks of the year, as well as the marine and aviation sectors. Ultimately, when you put it simply, what you are after is the most efficient use of renewable energy to propel your vehicle – whatever that solution might be.” E-Mobility Engineering | May/June 2025 Under the bonnet of the range extender REx car
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