Old-tech battery for new Toyota Prius

Electric vehicles and hybrids the world over are storing electrical charge in lithium-ion batteries, but not the Toyota Prius.

The current model is available overseas as a plug-in model with a lithium-ion battery, but has only ever been sold here with less efficient technology in the form of nickel-metal hydride. And that won't change with the introduction of a new (fourth-generation) Prius to the Australian market in February 2016.

Toyota, in a press release issued today, claims that the Ni-MH battery technology represents "the optimum choice to meet market requirements." The battery for the new car is smaller than that of the current model, and has been relocated under the rear seat to free up added luggage space – now 502 litres. Boot space is also increased by relocating the 12V wet-cell battery to the engine bay.

Other than the reluctance to go with lithium-ion for the battery, the new Prius is shaping up pretty well, based on the information contained within Toyota's press release. The new model retains a 1.8-litre four-cylinder engine with variable valve timing, but Toyota is claiming an improvement in thermal efficiency to 40 per cent – a figure comparable to diesel engines, and a world beater for petrol engines. All up, according to Toyota, mechanical losses have been pared back by 20 per cent by reducing internal friction.

A dual cooling system pumps coolant through at a reduced volume until the engine warms up, and low-viscosity oil further reduces internal friction. The pistons and air intake ports have been revised for improved swirl within the cylinder, and exhaust gas recirculation volume has been increased to enhance combustion.

Overall, the engine is smaller than before, and the transaxle is also shorter, with motor/generator units taking or delivering power through multiple axles, rather than the single, concentric axle of the third-generation model. The planetary gear set has been ditched in favour of a more efficient parallel gear cluster.

Toyota has developed a new modular platform – Toyota New Global Architecture (TNGA) – and the new Prius is the first model to benefit from it, enjoying a lower centre of gravity and 60 per cent increased body rigidity. A new power control unit has resulted in 20 per cent lower losses in the new car's electrical system, and the unit is smaller than before, allowing Toyota engineers to locate it above the transaxle.

Outwardly, the Prius is 20mm lower and the roof's high point has been shifted forward 170mm. This has helped headroom inside, and contributed to the new car's drag coefficient of 0.24Cd – a small step forward from the 0.25Cd figure for the third-generation Prius.

The forward field of vision has been expanded, Toyota says, by lowering the nose 70mm, and the rear of the bonnet has dropped 62mm.

Bi-LED headlights will be 'available' for the Aussie-spec Prius, but not necessarily standard.

Inside, the Prius has come in for thorough revision, leading to greater headroom, better seat comfort and 'optimum positioning' of the instruments and controls. High-resolution graphics are displayed in two 4.2-inch screen, with trip computer data appearing in the screen on the right and infotainment functions appearing in the left screen.

New safety features will include an upgraded active cruise control, pre-collision, intelligent park assist systems, blind spot monitoring and rear cross-traffic alert.

Measuring 4.5m in length and 1.76m in width, the new Prius will ride on a wheelbase of 2.7m. The four-cylinder engine is rated at 72kW and 142Nm, with the electric motor capable of producing 53kW.