“The first test bench results are quite good, but how does it drive?”

“We are in an exciting stage,” Claude Lehongre, project lead at Renault, says. “The Megane hybrid demonstrator is now fully developed and tuned, and we are nearly ready to drive the car to see how it performs.” Renault is developing a Megane hybrid with an innovative powertrain that runs on 48V. This is different from most hybrid vehicles that run typically at much higher voltages. Claude: “The advantage of a 48V system is it’s lower cost.” Using a higher voltage requires specific devices and more electrical insulation, making the car more expensive. “Normally a full hybrid is about 20% more expensive than a regular passenger car.” A 48V system is safer and less complex to build. “We expect we can reduce the cost premium from 20% to 10%.”

But running a hybrid car at 48V brings its own challenges. “The traction power is very different,” Claude explains. “In a full hybrid passenger car you can have up to 30kW available for traction, so changing from the internal combustion engine (ICE) to hybrid drive is easy. A high voltage system has enough power to boost the acceleration.” Instead, 48V gives less output power. “One difficulty is to manage the restart of the ICE accurately. Changing from hybrid drive to the thermal engine needs to be smooth, that is key.”

Currently we are performing CO₂ measurements with the ECOCHAMPS demonstrator vehicle. Claude: “The first results from the test bench are promising and now we are assessing drivability. I am excited to see the results, because that is also what customers will look for. Does it feel right, is it fun to drive?”