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What is a hybrid car? Batteries, PHEVs and plug-ins explained

Published: 08 October 2018

► CAR magazine guide to hybrid cars
► All about PHEVs and hybrids 
► Tech explained, jargon debunked 

Hybrid cars are partly electrified vehicles that still rely on an internal combustion engine to either drive the wheels or charge the battery. Unlike a full electric vehicle (EV), they have a petrol or diesel engine to fall back on if your electricity supply is running low.

As such, hybrids are the stepping stones between the fossil-fuel age and the new era of electrification. Buy one if you want to reduce your CO2 emissions, save fuel, dodge congestion charges and potentially lower your tax bills.

In this article we explain the major types of hybrid car on sale in 2018 and give a little background on each sort. If you’re thinking of going full electric, don’t miss our guide to the best EVs on sale today.

The three different types of hybrid car

Hybrid cars have been around for two decades in series production: Japanese manufacturers have led the charge, and the Honda Insight and Toyota Prius were both launched within months of each other in the late 1990s.

Hybrid cars come in all shapes and sizes

If you’re looking at buying a hybrid vehicle today you will likely face a barrage of jargon and we’ve tried to untangle the language in our handy guide.

All our hybrid car reviews

What is a full hybrid car?

A full hybrid is a car which can drive under its own electric power, petrol or a combination: an electric motor onboard is capable of driving the wheels under full e-power for a short distance, although most of the time the car will be driven by a mixture of combustion engine and electric motion. They are sometimes called parallel hybrids.

Examples of full or parallel hybrids include cars like the Toyota Prius and the BMW 330e. Their batteries are typically small-capacity and they’re optimised for mixed running in daily driving, rather than extended zero-emissions electric range.

What is a plug-in hybrid car (PHEV)?

A plug-in hybrid is often also referred to as a PHEV, standing for Plug-in Hybrid Electric Vehicle. The name even makes it on to the side of the car sometimes - see the Mitsubishi Outlander PHEV, for example.

Electric cars: hybrids are a stepping stone to full electrification (Getty)

In a delightfully Ronseal fashion, a plug-in hybrid does exactly what it says on the tin: you can plug it in to charge up the batteries when you’re at home or on a long journey (just like an electric car, above). This means you can provisionally start every journey with a full battery, maximising your chances of driving into city centres on silent and zero-emissions EV mode.

Examples of PHEVs include the BMW i8 and VW Golf GTE. They typically have bigger battery capacities to enable their longer electric range (typically around 20-30 miles today).

What is a mild hybrid?

The phrase ‘mild hybrid’ can be misleading. A mild hybrid car is one which cannot drive under electric power alone; instead an e-motor is only used to assist the powertrain. 

But some manufacturers also use the phrase to denote energy-saving systems designed to cut the engine at standstill and harvest power during deceleration. The Suzuki Swift 1.0 Boosterjet SHVS is one example of this: it can never run on electric power alone and its wheels are never turned by an e-motor, but its drivetrain does use fuel-saving tech to reduce consumption.

What is a range-extender or REX hybrid car?

Yep, yet another category of hybrid… REX stands for Range-Extender electric vehicle, meaning the internal combustion engine onboard is only ever used as a generator to charge the battery of an EV, rather than to drive the wheels. The BMW i3 REX (below), Vauxhall Ampera and Chevrolet Volt are good examples of the genre.

BMW i3 REX plug-in hybrid electric vehicle (PHEV)

These range-extenders are also sometimes called a series hybrid (so named because the electric motor always drives the wheels - the internal combustion engine (ICE) is plumbed straight into the electric drivetrain, rather than the wheels on the road.

So how do I charge a hybrid car?

Most hybrids are charged automatically without any intervention by the driver. Regenerative braking uses energy wasted during braking or coasting to recharge the battery, with lots of little micro top-ups during normal driving. Toyota has even started calling its models ‘self-charging hybrids’ to convey this to buyers.

The exception to this rule is a PHEV, which can be plugged into an electric plug to top up the battery: this can be done either at an EV charging point for faster charging or a domestic three-point plug if you’ve got time for a slow trickle charge. 

Our guide to UK electric car charging infrastructure

How does a hybrid car work?

As you can see from the above, the level of complication in a hybrid electric car varies hugely. All but the most basic mild hybrids have electric motors to drive the wheels and an extra battery pack to power the e-motors.

Hybrid cars typically juggle power from electric and internal combustion engines

The clever bit comes in the power control electronics, which juggle the different power sources. Most do this quite seamlessly, so the driver merely steers, stops and goes - there are rarely other buttons to confuse things (apart from an EV button on some full hybrids, to select full electric drive around town).

The majority of hybrids are automatics, so you don’t have to change gear. You’ll usually find a Continuously Variable Transmission (CVT) gearbox, designed to maximise economy and deliver torque or pulling power when you need to accelerate fast.

Hybrid cars for sale

Browse a mix of hybrids for sale in our classifieds listings here. Secondhand hybrid cars have proved popular with minicab drivers and other urban dwellers, suggesting that fears over the longevity of batteries is unfounded.

Should I buy a hybrid car?

Motorists looking to reduce their running costs should consider a petrol-electric or diesel-electric car; if going the full hog and picking an all-electric car is unrealistic for drivers doing longer distances, a hybrid could be just the stepping stone car you need.

By CAR's road test team

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