Speaking at the EROAD Fleet Day in Christchurch, New Zealand, eMobility Division Manager at TransNet, Glenn Inkster, highlighted the need to simplify EV charging for fleet buyers.
“One of the challenging things with understanding EV charging is this statement here, ‘an EV with a 7.4 kilowatt onboard charger will charge at 3.7 kilowatts when plugged into an 11 kilowatt charging station’,” Mr Inkster said.
“You can go do an electrical apprenticeship for four years and still find this confusing!”
Mr Inkster believes EVs need to be simplified, much like internal combustion engines have been across a century of use, making ‘driving’ the priority.
“The biggest challenge we have is simplifying, because engineers are brilliant but they have a habit of making things more complicated than they need to be,” he said.
“You certainly don’t need to know the fuel pressure of your petrol road car, it doesn’t matter because you just get in and drive it.
“We need to get to a point where we just get in and drive EVs.”
The issue, Mr Inkster explained, is a flawed understanding of electricity which is made worse by industry terms like ‘power’ used to describe energy output.
“There’s two terms that matter when it comes to electricity, and they’re power and energy,” he explained.
“We all talk about our power bills but it’s actually our electrical energy bill.
“Use one kilowatt of electrical power for one hour, and you’ll use one kilowatt hour of energy. What if you need two kilowatt hours of energy? Well, it’s pretty simple.”
Breaking things down for the audience, Mr Inkster went back to basics explaining the principles between electrical energy and power – rudimentary knowledge for some, but foreign concepts to many EV owners.
“Now remember that the kilowatt hours is the energy storage in the battery, so that’s the maximum amount of storage you have, which dictates how far you’re going to go,” he said.
“Power is kilowatts, energy is kilowatt hours. Understand the two and it makes everything else easy to understand.
“Every other term we hear, like charge modes and combined charging systems, it’s all pretty much about turning one of those two into the other or back the other way.”
For fleet operators assessing their charging requirements it is important to consider the cost of fast charging compared with slower charging, which will ultimately affect the operating costs of vehicles.
“So you can either charge, or add energy, with a higher power for a shorter time, or a much lower power for a longer time,” Mr Inkster explained.
“So, without doubt, the faster you charge the more it will cost because it’s the amount of power that costs the money .
“It’s no different to a petrol car, because if you want a 300kW petrol engine it’s going to cost you more than a 100kW engine.”
After explaining the fundamentals of power versus energy, Mr Inkster also debunked common misconceptions around AC and DC charging – in particular how little energy a domestic outlet will actually provide.
“We often think you can just plug in the car to a little domestic outlet and you’re charged, but it’s not going to happen,” he said.
“Let’s compare the maximum 15 kW a house will use if you turn everything on and compare that with a 350kW DC charger.
“If you use 15kW at your home your energy bill is going to be $2500 per month and clearly you don’t go anywhere near that.”
Putting things in perspective, Mr Inkster outlined that to achieve the equivalent refuelling capacity of 45 fuel pumps, it would require around a quarter of the energy output of the Hoover Dam which provides power for Nevada, Arizona and California.
“We always need to respect the electrical supply when we talk about charging, because it’s the biggest challenge we’ll have,” he said.
“If you want to match what 45 fuel pumps do you’d need 165,000 kilowatts, which is about 25 per cent of the output of the Hoover Dam.
“So we can start to understand the challenge that we have if we think we’re just going to replicate our petrol habits with an EV.”
Mr Inkster pointed out that all DC batteries, like those found in EVs, require AC power to be converted using a charger, but even DC ‘fast chargers’ are still slow compared with refuelling a combustion engine vehicle.
“If you have a DC charger, it’s DC power going to the car and even though we call it fast charging, it’s still very slow at replacing energy compared to our petrol habits,” he said.
There is a solution, Mr Inkster explained, but it requires both a shift in thinking and charging habits.
“The requirement to replace energy quickly, like we have with petrol, is exchanged with charging when you’re doing other things,” he said.
“Start every day fully charged and have one AC charging station for every fast charger. Stop talking about fast charging, let’s start talking about convenience charging.
“Convenient charging is sometimes fast, but it should always be the slowest possible within the time available, because the faster you charge the more it all costs.”
The TransNet solution is to start thinking about the terms ‘range’ and ‘capacity’, deciding how far your fleet vehicles need to travel and what that will require.
“They’re very simple questions that anyone can answer, so instead of kilowatt hours and amps and PDAs and all that complicated stuff – use range and capacity,” Mr Inkster said.
Mr Inkster pointed out that businesses need to think about total required range across their fleet each day when assessing charging requirements, too.
“If we’re planning our car park of 40 cars, do you really think we need 40,000 kilometres of range-adding capacity per day?” he asked.
“When we keep asking for kilowatts, we get it so mismatched because 40,000 kilometres, if your car can take it – which it won’t – would be 22 kilowatts and 11 kilowatts would give you 20,000 kilometres per day.
“Take a step back, find out what you actually need, and get the right-sized charging infrastructure because, remember, it’s the electricity grid that’s going to cost you money.
“Control rate is much more important than the ultimate speed of charging, so things like power sharing, things like monitoring the supply going to your building – use what’s left over and you’re going to get a result without having to spend huge amounts in upgrade costs.”
An example of the pragmatic TransNet approach was highlighted when a customer, Mr Inkster explained, requested 40 chargers capable of 22kW output. A number he said is akin to “asking for a road car with 5000hp”.
“Instead of that, we worked with the supply that was there, added even more range-adding capacity than they even needed, but they still had plenty of scope for adding chargers in the future and they didn’t have to upgrade the transformer,” he said.
For fleet operators experiencing range anxiety, Mr Inkster explained that the solution is to calculate average kilowatt hour use per 100 kilometres which provides an accurate and repeatable driving distance.
“The most important piece of information is the kilowatt hours per 100 kilometres,” he said.
“If you know how much energy you have and how fast you’re going to use the energy, you know how far you can go.
“So know the battery percentage on the dash, know the average kilowatt hours per 100 kilometres, know the range!
“Remember, range anxiety is simply that you’re not sure you’ll get where you want to go.”
What does calculating range look like on paper? Mr Inkster broke it down for the audience, reminding them to monitor average energy use the same way they would keep an eye on the fuel gauge of an ICE vehicle.
“If you take a 64 kilowatt hour battery, which is the amount of energy, and you’re going to use it at 20 kilowatt hours per 100ks on average, that’s your range – there is no guesswork,” he said.
“As long as I don’t go over that average, and it’s displayed smack bang in the middle of the dashboard, I’m going to make it every time.”
TransNet are EV infrastructure experts, offering products and installation for all EV charging needs, with more than 20 years of experience in the electrical industry.
