Haven’t electric vehicles had everyone in a lather lately?
Well, maybe it’s time to demystify the debate a bit and just answer a few basic questions about what EVs are and how they differ from the petrol-or diesel-fuelled car you’re driving right now.
Which electric vehicle are we talking about?
We’re focusing on battery electric vehicles (BEVs), which store their electricity in a battery and are powered solely by an electric motor.
So, not fuel cell electric cars that carry hydrogen in a tank and refine it into electricity onboard. They’re still not feasible production vehicles in Australia as yet – or any other place for that matter.
Nor are we assessing hybrids of any description – from plug-in to mild – that combine electrical power with a traditional petrol or diesel internal combustion engine. They’ve been around since the late 1990s without starting federal election scare campaigns.
No, it’s the BEVs that are the source of all the controversy – as fake and foolish as it is.
As we’ve reported here already, whether it’s Scott Morrison or Bill Shorten who dosses down at the Lodge after May 18, we’re going to see more and more battery electric vehicles on-sale in Australia.
What’s the nuts and bolts?
A BEV is powered by a motor – some BEVs have more than one – that converts electricity into the mechanical energy driving the wheels.
There are variations in the way they are constructed, but all electric motors rely on a stator to generate an electrical field and a rotor which is being moved by the electrical field.
Electric motors have a couple of great advantages over orthodox internal combustion engines. They are far more efficient, they produce maximum pulling power (or torque) from zero revs for better acceleration, and there is really very little to go wrong with them.
“The power density of electric motors is really something that cannot be beaten by an internal combustion engine”, said Xavier Casley, a compliance engineer at Tritium, the Brisbane-based developer and exporter of electric vehicle fast chargers.
“You can have something that weighs 50 kilograms and will happily put out 300 horsepower any minute of any day of the week.”
Then there’s emissions. An EV produces no CO2 or particulates, although, as is widely known, that picture becomes less pristine if you’re not drawing your electricity from a renewable source.
Electricity is stored in a battery pack – thousands of chemical cells – that sit under much of the floor of the vehicle. Most BEVs use some variation of a lithium-ion battery chemistry.
The battery is the most expensive and heaviest component in a BEV. Its combination of rare-earth metals and high-tech are much of the reason they are so expensive.
Batteries are also a key differentiator between different BEV brands: “You get into to the nitty gritty of it, there are different constructions and chemistries,” Casley explaind.
“Tesla actually uses a different chemistry to Jaguar; Audi uses a different one to Tesla. Porsche is different again.”
So let’s go back a step
What is electricity? Yep, dumb question, but here’s the answer: it’s the movement of electrons between charged particles. That’s it.
A chemical reaction inside a battery makes electrons flow between positive and negative charges. They can generate heat, operate switches and spin an electric motor. That’s where BEVs come in.
A BEV actually uses two types of electricity. Alternating current, or AC, is what comes out of your wall socket because it’s easier to transmit over distance from the power station. So when charging at home that’s what goes into an EV.
But the AC is converted to direct current, or DC, on the way to the battery pack because that’s how batteries store their energy.
But electric motors are AC, so a sophisticated bit of gear called an inverter converts the DC when it’s called upon. It also controls the speed and torque of the motor, otherwise it would run flat-out all the time.
The next step is DC fast charging, but we’ll get to that in a sec.
A few terms you’ll be hearing more often in the future
Current/amps: This is the flow rate of the battery; how much energy it can push out and how quickly it can push it out. More amps means better response. But it also means the potential to drain the pack sooner, as well as needing larger cables, more space, more weight and more cost.
Voltage: Voltage is the electric potential of the battery pack. If you want to use an internal combustion engine analogy, more volts is like having more cubic centimetres. More volts, the faster you go. Most BEVs top out at 400 volts, but 800-volt systems are starting to appear. Going up in voltage means you can go down in amps for the same amount of power, reducing cable size, weight and cost. You get more volts and/or current via battery chemistry and the way the pack is constructed from the smaller cells.
Kilowatt-hours per 100km, or kWh: Commonly referred to as kilowatt hours, this is the accepted way to describe the size of a battery pack. It is the measure of energy based on its chemical storage. Everything else being equal, if your EV has more kWh than another one, you’ll have a longer range. Kilowatt-hours per 100km: This is how you measure fuel consumption, or the electrical equivalent of it.
A smaller, lighter EV supplied by a battery pack with less kWh (see above), should be more efficient than larger heavier EV. Which means their range could pan out to be about the same. This weight and consumption issue is why some transport experts reckon hydrogen fuel cells make more sense for future heavy vehicles, such as trucks and buses, than going battery electric.
Refuelling – sorry, recharging
One of the best features of EVs is the electric motor’s ability to generate electricity as well as consume it.
Lift off the throttle and the motor will literally think it’s driving in the other direction and send power to the battery pack rather than the road via the wheels.
Modern brake regenerations systems are so good you can drive most of the time without using the mechanical brakes. You can even adjust the intensity level of regen and braking in some modern EVs.
In theory, that means you used no energy while cruising you may never have to charge your EV via a cable … but you invariably you will.
The slowest way is using the 240v wall socket at home hooked up to your car via its onboard AC charger. These systems – with very few exceptions – take many hours to fully recharge a depleted battery.
Take the Hyundai Kona electric as an example. Plug it into the wall and it will take 21 hours to recharge the 64kWh battery. Option the $1950 7.2kW onboard charger and it will take about nine hours to recharge.
This recharging time is now a much bigger issue than the actual driving range of EVs (referred to as range anxiety), many of which now have ranges of more than 300 kilometres.
The solution to this issue is the ever-expanding network of DC fast chargers that can dump electricity into a battery pack at a much faster rate.
These days there are plenty of 50kW chargers around and 100kW chargers are starting to pop up. Take that Kona electric as an example and, all of a sudden, we’re talking 50 to 70 minutes for a recharge.
Of course that’s still a long way from the five minutes to refuel a petrol car, but with 350kW – and even one megawatt (1000kW) – DC fast chargers on the way, parity is looming.
“We are not far off right now,” Casley said.
“A lot of cars now will charge in 30 minutes.”
Yes, the batteries in your BEV will degrade over time, probably a little bit quicker if you repeatedly fast-charge or constantly operate in extreme temperature conditions.
But Casley said the issue was much more pronounced a few years ago, when battery packs weren’t cooled as well as they are today.
“The great thing about [modern BEVs] … is they actively thermally manage their batteries, they try to keep them in a safe temperature range. They have got liquid flowing through the battery pack all the time cooling it down,” he said.
He estimates a battery might drop 10 per cent of its performance in the course of thousands of recharge cycles over 10 years.
“That’s equivalent to hundreds of thousands of kilometres in a petrol-engined car.”