Welcome to the latest installation of a 5-part series about environmentally-friendly cars, entitled Green Machines. To read the previous installation, CLICK THIS LINK. For the next post in this series, CLICK THIS LINK. To start at the beginning, CLICK THIS LINK. Thanks for reading!
Fully Electric Vehicles (EVs)
Ben Franklin invented the first ever electrical device. It was a key that glowed in the dark when attached to the string of a kite, flown during a thunderstorm. As you can imagine, this key had only limited practical use.
The same can be said of today’s fully electric vehicles (EVs). At least, for my purposes.
For all their wonderful advantages, EVs have three major drawbacks. The first is limited range. The second is their tendency to have less range at highway speeds than while driving in the city. And the third is the amount of recharging time required.
Most affordable EVs on the market these days have a range of 200 – 300 miles. The Tesla Model S Long Range has the most range, estimated to be about 405 miles. However, those extra miles will set your wallet back about $85,000.
But who needs more range than 300 miles? Aren’t there plenty of charging stations around these days to handle a quick recharge and get you back on the road? There are, and their number is growing. As of the start of 2021, there were 96,536 public charging ports in the USA. That’s up from 63,303 as of March 31, 2019.
Still, there are some long stretches across the Great Plains and West that might leave you dripping in sweat, wondering if you’re going to make it to the next station.
Now, once you make it to a recharging station, you’re faced with the issue of charging time. Most charging stations have adapters to handle most brands of EVs. So, if you’re driving a Nissan Leaf and you arrive at a Tesla station, it’s likely they’ll have an adapter to handle your charging needs. That’s very nice and convenient.
But the bad news is, it’s going to take some time. The best way to recharge an EV is through a slow, trickle charge, that can require many hours. Slow charging is less wearing on a battery, and it allows a battery to fully charge. And this is okay if you’re at a hotel and plan to spend the night. But if you just want to get back on the road real quickly, you’ll need to opt for a fast charge.
Fast charges take about 15 minutes. But unfortunately, they only charge your battery up to 80% of its capacity. Once they reach the 80% mark, they slow the charge down to keep from overheating your battery and destroying it, or causing a fire. So you’ll have to settle for an 80% charge if you’re in any hurry. Thus, if your car normally has a 300-mile range, you’ll have to settle for 80% of that, or 240 miles, from a quick charge.
Also consider that you wouldn’t want to drive your car completely to the end of its range, before looking for a charging station. That could leave you stranded out in the middle of nowhere. For peace of mind, you’d probably want to pull in for a recharge while having something around 50 miles of range left. But such peace of mind will cost you, by diminishing your now 240-mile range car to just 190 miles.
These are things to consider when buying an EV with the idea of cruising around the country.
Another consideration is loss of range from highway driving. EVs present an anomaly when it comes to fuel economy, compared with gas cars. Gas cars get less miles per gallon in the city than on the highway. But when equivalent miles per gallon (MPGe) are calculated for an EV, they get more MPGe in the city than on the highway. For instance, the Mustang Mach-E gets 96 MPGe in the City, but only 84 MPGe on the highway.
What in the hell is going on here? It’s a scientific fact (I think) that both gas engines and electric motors tend to be less efficient at higher revolutions per minute (rpms) than at lower rpms. So why the stark contrast in miles per gallon?
The answer lies in gearing. Gas engines have an optimum rpm for any speed they drive, sometimes called the “sweet spot,” and at that sweet spot they are the most energy efficient. But in the city a gas car is constantly changing gears as it speeds up and slows down. Much of the time the engine is not at the sweet spot for the gear it’s in. And so it operates inefficiently and wastes fuel.
But on the highway, at steady speeds, the transmission easily finds its best gear and keeps the engine in its sweet spot. Thus, the engine is able to run more efficiently, even though its rpms are faster than they are in the city.
However, the electric motors of EVs are different. They have no transmission. That’s because they don’t need a transmission. When it comes to electric motors, their rpms are always at or near their sweet spot for whatever speed they travel, whether in the city or on the highway.
However at faster highway speeds, higher rpms and aerodynamic drag work against an EV, the same as it works against any kind of car. And this reduces their efficiency, causing them to be less energy efficient on the highway.
Also, most EVs, and even most hybrids, are designed with regenerative braking. Whenever an EV slows down, generators in the braking system absorb some of the braking energy and transfer it to the batteries, recharging the batteries somewhat. This reduces the inefficiency caused by frequent slowing down in the city, and helps to extend range.
But just the opposite is true from highway driving. While higher rpms and wind resistance reduce efficiency on the highway, there’s little or no regenerative braking going on, to offset that inefficiency. Without this advantage, EVs tend to have less range on the highway, than in the city.
Therefore, don’t expect your 300-mile range EV to actually reach 300 miles on the highway, between charges.
The Environmental Protection Agency (EPA) has a formula for calculating combined range. It combines expected city range with expected highway range, determines some sort of average between the two, and comes up with an EVs “combined range.”
However, Car and Driver (C&D) magazine recently cast some doubt on the EPAs figures. They tested the highway range of 12 EVs, and found that they can be anywhere from 62% to 93% of the EPAs combined range rating. For instance, the 2019 Audi e-tron has an EPA combined range of 204 miles, but a C&D tested highway range of 190 miles. That’s 93% of combined range. Meanwhile, the 2019 Hyundai Kona Electric has an EPA combined range of 258 miles, but a C&D tested highway range of just 160 miles. That’s just 62%.
Thus, after a quick recharge at a highway pit stop, that Kona may only have a highway range of 160 X 80%, or 128 miles (remember, quick recharges only bring a battery up to 80% of capacity). For peace of mind, you’ll want to lop about 50 miles off of that. And this leaves you with a practical highway range of just 78 miles. That’s a far cry from the EPA rated 258-mile combined range that might influence you to buy the car.
The Porsche Taycan
I’ve asserted that electric cars have no transmissions, but the Porsche Taycan makes a liar out of me. It has a 2-speed automatic transmission on its rear axle. Porsche claims that this improves acceleration at low speeds, and extends range at higher speeds. However, it still only has a range of 227 miles.
In theory, a 2 or 3-speed transmission can improve the performance and range of an EV. However, transmissions add complexity and weight, and this offsets the advantages of multi-gearing to such a degree that it only has practical usefulness in expensive, high-performance EVs, such as the Taycan. And even that usefulness is questionable.
Based upon all this research, I’ve been able to cut through the hype surrounding EVs, and decide that I don’t want one. I love my brother’s Mustang Mach-E, and feel relieved that he bought it for city use, and not for long-distance driving. But the car I want is not for city driving. It has to handle long road trips.
So I want a car with good range, for all the road trips I like to take with my wife. I also want reliability. EVs tend to be very reliable, due to their simplicity of design, and lack of an internal combustion engine and transmission. There’s not as much to break down, with an EV, than with a gas engine car. But unfortunately they just don’t have near the range I need.
But that doesn’t end my search for a green machine. There’s more to green driving than EVs. We also have HEVs. An HEV is a Hybrid Electric Vehicle. And when it comes to range and reliability, HEVs often meet or exceed what you’ll find in a conventional gas-powered car.
We’ll be jumping into my HEV research, and giving it a test drive, in my next post.
Some of my sources:
Categories: Series (Science): Green Machines