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Kia will launch a new version of the Sportage SUV later this year, using a 48-volt mild-hybrid diesel powertrain. The Korean car maker claims that the new system increases fuel economy and trims emissions by around four per cent, on the new WLTP economy and emissions test.
48-volt systems are much cheaper, lighter, and simpler than conventional hybrids, and can be 'bolted-on' to an existing engine, as Kia is doing with the Sportage. It won't drive the car under pure electrical power at any point, but it is better at harvesting regenerated energy from braking, can aid the engine under acceleration, and has a much more effective stop-start system, as well as being capable of high-speed 'sailing' - shutting the engine down for a few seconds at a time on the motorway to help save fuel.
Kia's 48-volt system uses a very compact 0.46kWh lithium-ion battery, and a new Mild-Hybrid Starter-Generator (MHSG) in place of the alternator and starter motor of old. That MHSG can add as much as 10kW of extra power to the engine when needed, which can both improve acceleration, or provide power to run ancillary systems such as air conditioning, to reduce the load on the engine, thereby also reducing emissions and fuel consumption.
It can both harvest otherwise wasted power from the brakes, and also can use the drag effect of the crankshaft when coasting in gear to charge up the small battery. That also means that it has a 'moving stop-start' function, whereby the engine can actually be shut down before the car comes to a complete halt, extending the stop-start cycle and helping to save fuel around town.
As part of this virtuous circle, that also means that the 12-volt battery that powers the car's conventional systems can be smaller and lighter than normal. The car has a DC/DC convertor to allow the 48-volt system to power the existing 12-volt architecture.
Kia says that, once it has launched the 48-volt system in the Sportage later this year, it will be the first car maker to offer hybrid, plugin-hybrid, and 48-volt mild hybrid models. The same engine-and-48-volt system will go into the new Ceed hatchback in 2019, and Kia says it is also working on a petrol mild-hybrid setup. It's part of a plan to offer 16 new 'advanced powertrain vehicles' by 2025, including five new hybrids, five plug-in hybrids, five battery-electric vehicles and - in 2020 - a new fuel-cell electric vehicle.