If you’re interested in moving to a new type of motive power for your personal wheels, but you’re confused by BEVs, HEVs, MHEVs and PHEVs, and whether they’ve got the right sort of range for you… well, we’re here to help. In this piece, we’ll be looking at the two types of electrified car that offer the most range possible and also assessing how you can avoid the pitfalls that will eat into your theoretical maximum range. Read on to find out how to switch away from a diesel to a car that’s powered, at least in part, by electricity.
EVs versus PHEVS
Right, so an EV is an electric vehicle – this is a pure electric car, with no combustion engine on board at all. It relies entirely on its battery pack (currently mostly lithium-ion) to get its motive power, so once the battery cells are out of charge then the car will need to be plugged into an electric source before it can move any further. As you can’t exactly walk to your nearest electricity station and fill up a can with volts, this is why people suffer range anxiety with electric cars; if they run out of juice in the wrong place, it’s not going to be much fun trying to get them sorted out afterwards.
So, while battery companies work on the technology to give their products ever more capacity and, in turn, electric cars powered by them more range, the compromise is a plug-in hybrid electric vehicle. This teams the battery pack and electric motors of an EV to a combustion engine – almost universally petrol, although Mercedes has recently announced the E 300 de PHEV diesel. Anyway, the idea of these PHEVs is that you have a certain amount of pure-electric (zero emissions) range, but once that’s exhausted, you can use the combustion engine as normal to continue your journey. Said engine and also kinetic energy harvesting (from braking) can then recharge the battery pack of the PHEV on the move, although the best way to get the batteries back to full health is by plugging the car into the mains, as with an EV; this is what distinguishes a PHEV from every other type of hybrid car, which will have far lower all-electric range capabilities and no port into which a mains-electric charging cable can be plugged.
Confusing the issue slightly are the rare ‘range extenders’, of which there’s an obvious one – the BMW i3 REx. This is where an electric car is augmented by a small petrol engine (in the case of the i3, a motorcycle unit), whose only purpose is to serve as a generator to keep the battery topped up while on the move and thus extend an EV’s range; the engine never drives the wheels. However, despite this unusual arrangement, the inclusion of a petrol motor means that range extenders technically classify as PHEVs, albeit PHEVs unlike any others.
Battery packs for electrified cars are rated in kilowatt hours (kWh), which is a method of measuring their storage capability – rather like looking up the fuel-tank size of a combustion-engined car, to work out how far it will go on one tank of petrol or diesel. In general, the rule to remember is that the larger the kWh number, then the greater the all-electric range: it is pretty much as simple as that. Pure EVs have far larger battery packs in kWh than PHEVs, because manufacturers don’t have to package all the cooling and mechanical ancillaries that go with a combustion engine in an EV, so the battery pack can be physically huge; they are usually mounted in the floor of the electric vehicle in question, for packaging and weight distribution purposes.
The sizes of these batteries on current EVs ranges from smaller, city-focused machines like the BMW i3 (29kWh, quoted maximum range 314km), and the Nissan Leaf/Renault Zoe (40kWh, max range 403km) to the new breed of electric SUVs, such as the Audi e-tron (95kWh, 400km) and Jaguar I-Pace (90kWh, 470km), and then ultimately to the most famous electric cars of all – Teslas, which can have 100kWh batteries and claimed ranges of up to 610km.
PHEVs, in contrast, have to get an engine and gearbox and so on into their body shell, so their batteries are normally rated at around 10kWh, give or take. The BMW i8, for instance, has a 7.1kWh item, while the Mitsubishi Outlander PHEV’s stands at 13.8kWh. This means they go much less distance on electric power alone, with most PHEVs giving between 25- and 70km in zero-emissions mode. However, the benefit comes not only with the mental ‘comfort blanket’ of having a combustion engine to fall back upon once the electricity has run out, but also in shorter charging times: the bigger a battery, the longer it takes to ‘fill’ – just like a fuel tank. PHEVs can be topped back up in a matter of minutes on fast chargers, or in about four hours (roughly) on nothing more advanced than a domestic socket. Plug a Tesla 100kWh EV into the mains at home and you’ll be waiting for the best part of an entire day to get any meaningful range into it. This is why EVs are dependent on rapid chargers, rated at 100kW (150kW, in the case of Tesla’s ‘Superchargers’), which refill a battery’s capabilities in much less time. Even so, on a Supercharger, a Tesla 100kWh model will take 40 minutes to get 80 per cent of its charge back.
What affects range?
The same sort of stuff that would affect fuel economy in a conventional car: vehicle weight, aerodynamic drag, landscape topography, driving style, the external ambient temperature and any drains on the electrical systems – in vehicles, these would include, but not be limited to, the cabin heating, exterior lights, the stereo system and the windscreen wipers. This is why all manufacturers, when citing the maximum range for an EV, often then talk about the real-world range of said EV and it’s often a lot lower – the Zoe, for instance, has an real-world range of about 280km, which drops by another 60km to 220km in winter. This is because, if you’re driving an EV on a warm, dry spring day, with no radio on, then you’re not making any extra demands of the electrical system beyond motive power. If it’s a dark, grimy winter’s night, though, and you like listening to sport on the radio, then you’ll have the car’s heater on, the wipers going, the headlights blazing… all of which eat into the EV’s range.
Heavier cars are also going to have their range stunted, hence why the likes of the Jaguar I-Pace and Audi e-tron – both weighing well in excess of two tonnes – only have the same claimed theoretical range as the much lighter, smaller Nissan Leaf and Renault Zoe city cars, despite having battery packs that are more than twice as big in terms of storage capacity. If you’re lead-footed, enjoying driving fast and accelerating hard, or you happen to live in a mountainous area with lots of uphill routes, these factors will also reduce electric range. Don’t stick a bike rack on the roof of your EV and then leave it there all the time, even when you’re not carrying bikes, as that will increase drag on the car and reduce range in turn. And if it’s simply cold weather outside, you’re still going to have less range than you would if it was warm, because the battery pack’s effectiveness is reduced in freezing temperatures.
All the same things affect a PHEV’s pure-electric range, of course, but at least there you have the traditional fuel system to fall back on to ensure you make it home. Bear in mind a PHEV’s official combined maximum range is likely to be well in excess of any electric car’s figure, barring the bigger Teslas, because the fuel range and battery range are added together. However, PHEVs – even under WLTP testing – are often cited as having incredible fuel consumption figures (around and about 2.0 litres/100km, or 141.5mpg), but this is because of a quirk of the official fuel economy testing processes. Once a PHEV has exhausted its battery power, the combustion engine is then being asked to haul around the weight of the vehicle PLUS the not-inconsiderable weight of the now-redundant battery pack and electric motors. This further impacts fuel economy, so much so that PHEVs – on long motorway journeys, where their electric power will inevitably be depleted – tend to use 9.4 litres/100km, or 30mpg; this is often much to the chagrin of people who bought them on the strength of official fuel economy that is sometimes four times better than you’ll actually get on a motorway. Therefore, despite their extra range, PHEVs are still best suited to semi-urban commuters who can regularly charge the car (at home and at work) to ensure it does as many kilometres as possible on electric power alone.
Anyway, the long and short of all the above is this – whether you go full EV or PHEV for a bit of extra peace of mind, to maximise your electric range you need to: drive smoothly and steadily; aim to drive in conditions that will put less strain on the electrical systems (so, during the hours of daylight, when it should also be warmer); and don’t add any unnecessary weight or aerodynamic drag to your vehicle. That way, you’ll get the most from your advanced new form of motive power.
Carzone - 13-May-2019