We Can Build The First Great, Cheap Electric Roadster Today

This is a plan for an electric roadster that might really work.

byPeter HolderithMay 27, 2022 11:49 AM
an MGB sports car.
Getty, Duracell
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Whether the date when internal combustion engines die ever arrives is debatable. But to be sure: Electric cars are here and probably here to stay. Yet, we haven't tapped into every potential advantage they offer. It's time we try to figure out—at least hypothetically—how to make them work in something small, affordable, and light. Think MGB, but modern and electric.

I've been pondering this, and I think I have a workable concept. Feel free to disagree in the comments, but before you call me out for being a clown—the juggling is just a hobby, Mom—read what I have to say first.

Benchmarking

I am not an automotive engineer nor a product planner, but I do have a degree in industrial design, which qualifies me to at least do some informed speculation. The first thing I thought about was existing offerings in the market. There's only ever been one electric roadster, so this is easy: the Tesla Roadster. I think the thing to learn from the Roadster is that this is all very, very possible.

The Tesla Roadster cost just over $100,000, a lot of money but not unbelievable. Especially when you consider Tesla was a boutique automaker when it built the Roadster. The basic specs also prove the idea is workable. It weighed just 2,877 pounds, which got its foot in the door. Likewise, its range of around 250 miles is more than adequate for a weekend toy. In fact, that weekend toy status is the crux of this whole idea. Small roadsters are naturally pretty efficient.

Battery Basics

What the Tesla Roadster leveraged—and what the first great electric roadster will need to leverage—is that very nature. Miles per kilowatt-hour is the language we need to speak. The battery will have to be 50-60 kWh to keep the weight acceptable, at least if we're using current lithium-ion tech. Solid-state batteries are a chat for another day.

The problem with really eeking out efficiency from the 50-60 kWh is that the range has the potential to fluctuate massively. This is due primarily to changes in ambient temperature. Luckily the roadster has an answer: These vehicles are often only driven when the weather is nice with consistent ambient temperatures—at least, in theory. Likewise, the relatively small battery will mean it can be topped up pretty quickly.

Another important aspect is keeping the weight down by limiting the mass of the battery cells and keeping our cooling simple. Liquid-cooling this pack would add a lot of weight and complexity. I thought air-cooling would be adequate. Is that a bad idea? Maybe. The Nissan Leaf is air-cooled, and its range suffers in extreme temperatures. However, the Mercedes EQXX concept—a very, very efficient EV—uses an air-cooled battery for the same reasons I want to: efficiency, compact size, and simplicity.

Floor-mounted batteries might work to maximize cooling surface area, but I don't think that's a good move. We need to keep this car low slung and keep the driving position low. A battery pack in the tunnel is a better solution for what we're doing, and we can make it the structural backbone of the car, very similar to the C8 Corvette. Some manner of active intakes at the front of the car—shutters, if you will—could manage the temperature of this tunnel-mounted battery and look good. Just imagine: If your EVs intake shutters are wide open other people will think, "That guy is really on it!" How cool is that?

Chassis and Body

Now that we have our layout, we should probably look at the ND Miata and Corvette to figure out how to make this roadster cheap. Both cars use extensive aluminum and some plastic parts. I think that's a good approach. Carbon fiber gets cheaper every year, but we have to leave it off the table to be an everyman's car. Of course, the devil is really in the details. Keeping the weight off would be something to tackle once serious design work starts.

And the design work would need to be meticulous. This car's body needs to be very aerodynamic. I won't put pencil to paper to design anything for you to all laugh at, but I do have some basic ideas on layout. In my mind, we could do a coupe-style Targa top like the Corvette, a true convertible with a retractable fabric top, or a full on/off removable hardtop.

Number three is probably the best in terms of efficiency and convertible enjoyability. We could very carefully sculpt the hardtop to give us maximum efficiency. Maybe even throw a solar panel on there as a gimmicky option. Removing a hardtop and storing it somewhere can be a serious pain in the ass, though. In practice, it would probably leave most buyers annoyed.

The Targa-style Corvette top; let's just say there are plenty of advantages there, but it's not really a true convertible, and we're trying to design an iconic roadster. There's still a convertible Corvette for a reason.

We need to offer both a retractable soft top and the first removable hardtop option. We need the soft top for this whole idea to be legit. Yes, it's dead weight when it's retracted and not aerodynamically ideal when it's up, but it's still an elegant solution.

Drivetrain

The amount of power this car has is, in my mind, really not important. I'll address it but what's critical is how the drivetrain works with the rest of the car's systems, like the brakes. Ideally, we'll use a compact drive unit like Lucid developed for its Air sedan to leverage electric motors' power density and efficiency. The Lucid drive unit above weighs just 162 pounds yet is capable of providing 670 horsepower. And we only need a fraction of that power.

What we need to do, though, is place the main drive unit on the rear axle and probably an ancillary one on the front axle. If you've read about the new Formula E cars, you're getting where I'm going here. We're going to greatly reduce the size and weight of the mechanical brakes and improve our car's efficiency/driving dynamics by leveraging the drivetrain's regenerative braking system. For spirited drives on backroads where braking and acceleration are cyclic, it makes little sense not to try and get most of that energy back unless it means our base price gets a serious increase.

In terms of power, I like the idea of between 200 and 300 horsepower—probably an even 250 if I had to pick a number. Electric cars feel fast and responsive even with as little as 200 horsepower. A suite of settings to control the car's regenerative braking and power output is essential for utilizing this power, though. Without going into too much detail, a dial that would allow me to turn the peak output of the motor down to use less charge and more or less the same thing to control how aggressive the regen is would be nice.

Some kind of segmented display to show how fast I was going at a glance would also be useful. Having gears for reference can help on a track or backroad when it comes to finding safe limits. I think we need something like that here.

Conclusions

How does this all add up? Well, let me begin by saying this is a sort of middle-of-the-road spec. Also, it's a compromise. We could also make the battery smaller for buyers who want even less weight or bigger for a grand touring model. The possibilities are endless. Let's read off the spec sheet, though.

Our electric roadster features a 50-60kWh battery. Thanks to its aerodynamic design, modest weight, and carefully considered drivetrain, it can manage 5-6 miles of range per kWh of battery. This gives us an optimistic driving distance of 300-360 miles. Wow, where can I place a deposit?

Thanks to featherweight construction utilizing an air-cooled tunnel-mounted battery pack, composite body panels, and aluminum chassis components, it weighs just 2,700 pounds. Combine that with 250 hp, and our roadster is fast, too. Want to stretch the car's legs in terms of range? Get the aerodynamic hardtop—with the solar panel, of course—and adjust your peak output down to washing-machine levels. Don't care so much? Go for the soft top, crank the power to 11, and enjoy a serene, spirited drive on a backroad with less unsprung mass than any comparable gasoline-powered roadster. Plus, speed notification lights just like your old manual transmission ensure you don't put the car into a tree. All starting at—wait for it—$29,995. The Chevy Bolt is $31,995. Come on. It's possible.

So while EVs' role in saving the planet might be a little overstated, they're definitely sticking around. What I'm saying is that the future is uncertain. We might as well try to get a good roadster out of it. Yes, we may lose money on every car. But hey, it'll be great while it lasts.

Got a tip or question for the author? You can reach them here: peter@thedrive.com