Toyota's PHEV has a modest electric range, but that's not necessarily all bad
Fuji, Japan — How much electric range is too much? In the case of pure electric vehicles, it's a moot question. Short of cramming a car with so many batteries that there's no room left for people and their stuff, current battery technology isn't even close to matching the driving range of an internal-combustion engine. At this point in the game, the answer is: if only ....
Ask the same question about a Plug-In Hybrid Electric Vehicle (PHEV), and the answer isn't that obvious. A PHEV still has a gasoline/hybrid powertrain so it can already match or beat the range of regular vehicles. The question is, how much of that range should be in pure electric (EV) mode and how much in hybrid (HEV) mode?
Or put another way, why does the new Toyota Prius Plug-in Hybrid have a EV range of only about 25 kilometres after a full recharge whereas the Chevrolet Volt can typically go 60 km before it needs to fire up its gas engine?
One simple answer to that question is that the home market is important to the plug-in Prius, and in Japan most people driver fewer than 20 kilometres per day.
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Photo: Jeremy Sinek
But before we dig deeper, let's back up a bit and define our terms. A conventional hybrid vehicle (HEV) combines an internal-combustion engine (ICE) with one or more electric motor/generators (EMGs). In some cases (mild hybrid) the ICE always drives the car but may receive assistance from the EMG; in others (full hybrid) the EMG can power the vehicle on its own for short distances at low speeds.
Either way, all recharging of the batteries takes place on board, with the EMG reversing roles to act as a generator, driven either by the ICE directly, or by the road wheels through regenerative braking.
At the other extreme we have pure BEVs (Battery Electric Vehicles) which are powered solely by the batteries and electric motor and which periodically need to be recharged by plugging into an external source.
The plug-in hybrid electric vehicle (PHEV) is a blend of HEV and BEV. Toyota believes that by encouraging "early popularisation of electricity-using vehicles," PHEVs are the ideal transition to full BEVs or fuel-cell electric vehicles.
While retaining its regular gas/electric hybrid power pack, a PHEV receives a larger battery pack that can be recharged by plugging it into a wall socket or charging station. Bigger than in a conventional hybrid, but still much smaller than a pure BEV would need, the PHEV's battery pack is sized to let you drive a certain distance on battery alone before the car reverts to normal HEV operation.
