Hybrid engines come in many forms – and with unique drawbacks

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There’s a button on the dash of the popular Toyota RAV4 Hybrid marked EV Mode. It switches the compact SUV to “electric vehicle only” operation.

It was welcome this week, approaching the traffic-clogged Lincoln Tunnel here going into New York City. I’d driven down from Toronto and – because I was driving quickly to make an appointment – burned much more gasoline than expected. Entering the 2.4-kilometre-long tunnel, the gas gauge said there was only 16 km of gasoline in the tank. I needed to preserve every drop.

A tunnel is an ideal place for a hybrid’s all-electric operation. If the vehicle is running only on the electric motor, it creates no noxious emissions into the enclosed air that must be pumped clear, and it makes no noise that resounds off the walls. I’d driven for 500 km almost non-stop, so surely the battery was as charged as it could be. I paid the toll, pressed the button and cruised silently into the stop-and-go procession under the Hudson River.

The RAV4’s motor lasted just over halfway before its battery was drained and the gas engine switched itself back on. What’s the use in that?

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These days, there are many variations of hybrid and electric powertrains. The RAV4 has a “full hybrid” engine, which means it uses a combination of gasoline engine and electric motor to save fuel and can drive – albeit briefly – with just the motor. A dedicated battery is charged through the driving of the vehicle: It takes waste energy primarily from the heat of braking and converts it to stored energy, which can then be used by the electric motor when needed.

Some other vehicles have “mild hybrid” engines, which always need the gasoline engine to drive the vehicle, but use the electric motor to share power, or help it run heat and lights and similar features when stopped. The original Toyota Prius and Honda Insight were mild hybrids; more recently, the previous generation Buick Lacrosse and Regal offered mild hybrids. Later this year, Fiat Chrysler Automobiles (FCA), which owns Ram and Jeep, will be introducing a new, optional 48-volt mild-hybrid system on its Ram 1500 pickup and the new Jeep Wrangler.

The stronger electric motor (compared with current 12-volt systems) will be able to launch the vehicle from standstill so the engine won’t need to run until everything is actually moving. This is a fairly inexpensive alternative for any size of vehicle to create extra power when needed under load but also conserve fuel; FCA estimates it can offer two-thirds of the fuel savings of a full hybrid at just one-third the cost. Other manufacturers are also developing mild-hybrid systems that could become commonplace in the next few years. Delphi estimates that one in 10 cars sold in North America by 2025 will be equipped with the 48-volt system.

And then there are plug-in hybrid electric vehicles, or PHEVs, which are designed to drive for relatively short distances on purely electric power – usually somewhere between 15 and 50 km. They can be physically plugged into a household power supply to replenish their batteries and their electric motors are intended for short-distance commuting or congested city traffic. Outside the city, for extra range, the gas engine offers unlimited distance. The best PHEVs can be set to only switch on their electric motors when you set them to and to recharge them from the engine if desired.

While battery electric vehicles (BEVs) have solely electric motors for their powertrain and can only refuel at a charging station, battery electric vehicles with range extenders (BEV-Rx) have small gasoline engines solely to create electricity. When the grid-supplied power runs out on a Chevrolet Volt or BMW i3, their electric motors can still be supplied with battery power created by a gas engine. The difference is that they always drive as an electric car, not as an internal-combustion car with a drained electric-motor battery, but they are no longer “zero-emissions” vehicles.

Most attention is currently on BEVs and they have the most generous government rebates in those provinces and states that subsidize their purchase. But they’re not the be-all and end-all of environmental transportation. Inherently, the vehicles are either very small and light (to increase range and power) or very expensive (because they have additional battery power, which is both costly and heavy), so their uses are limited.

The truth is that the small and light battery-powered vehicles are bought as replacements on the road for conventional vehicles that are also small and light, and which are already highly efficient. It’s the larger vehicles that need replacing if overall greenhouse-gas emissions are to be reduced and if less overall gasoline is to be consumed.

As such, there’s a purpose for all the hybrid variants and each has its pros and cons. “There is no ‘one-size-fits-all’ approach to meeting Canadian drivers’ needs,” Toyota Canada president Larry Hutchinson stated recently in a speech to auto-industry stakeholders, “so public policy focusing solely on the sale of zero-emission vehicles may miss the real target of overall greenhouse gas reduction.”

All hybrids use less fuel than their conventionally powered equivalents, but they all cost more, because they’re packing two separate power sources under their hoods, not just one. The mild hybrids are the least expensive but there are now very few of them – battery technology has evolved to allow even basic batteries to hold enough power for a short electric-only drive and consumers want this. It helps salve their conscience at the drive-through.

The RAV4 might as well be a mild hybrid, though. Accelerate with more than a feather’s touch on the throttle and the gas engine will activate; the slightest upgrade will be too burdensome for the electric motor. Try to drive in EV Mode on the flat and there’ll soon be a long line of traffic behind you, growing impatient at your snail’s pace.

It would have helped to have had a greater EV-only range to get through the Lincoln Tunnel, but that would need a more costly battery and electric motor that will turn away potential converts. It will also weigh more and so the vehicle will consume more fuel on the highway when it’s not in use.

A typical battery electric vehicle with a range of 200 km would need at least three stops to recharge along the way, each taking close to an hour at a fast-charger. But a hybrid SUV such as the RAV4, which doesn’t need its owner to have a garage with an electric supply or a charging station, and which saves some fuel by replacing gas with electricity, does just the trick.

My average consumption for the highway drive down was just under 8.0 litres per 100 km and that was driving at the higher end of the accepted speed limit. If I’d driven at the posted speed limit, my consumption would have been much closer to the official combined rating of 7.3 L/100 km. (When I filled up, the computer estimated my range at 600 km, but the tank of gas actually covered barely more than 500). A conventionally powered RAV4, however, has an official combined rating of no better than 9.0 L/100 km.

Toyota’s Hutchinson says that at this early-adopter phase of electrification, it’s essential to offer something to everyone, and that includes drivers of larger vehicles who can’t afford expensive Teslas and premium SUVs.

“As an industry – and as a country – our focus should be on overall carbon reduction, not just on selling zero-emissions vehicles,” he said. “Getting there will require a comprehensive approach that offers Canadian consumers a choice of technologies and related charging or fuelling infrastructure that meet a broad range of needs and will lead to an overall reduction of greenhouse gasses.”

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