At least it's not "How Lotus is going to build electric sports cars lightweight"? Seriously though, it's a little disappointing to see 66.4 kWh for a minimal two-seater that's supposed to represent the Lotus philosophy. Any 2-seater that passes for Lotus can easily expect 4 miles / 6.5 km per kWh in normal driving. That's a lotta range to be lugging around.

It would be nice to see a track focused version with half the battery capacity. Take advantage of the reduced pack volume and shorten the wheelbase for additional weight loss, now the weight can be on par with an ICE Lotus. RWD with CoG behind centerline and tighter polar moment than an Elise on top of EV torque sounds like an absolute handful; call it a Evropa and have some fun at the local autocross!

The problem is you need the extra capacity on the track because you use it more there.

In normal driving you accelerate to highway speeds and then coast, or you're in city traffic and benefit from regenerative braking.

On a track, you brake late on purpose because it's faster, but to stop that fast you have to rely more on traditional braking and can't recover the energy. Then you immediately want to accelerate back to high speeds again.

If you put a small battery in an electric track car, it would be flat in ten minutes.

If 28 kWh is enough for an entire Formula E race, I think 33.2 kWh in a Lotus would work out okay.

28kWh isn’t enough for a Formula E race. They swapped cars in the middle of the race back when they used those smaller batteries. They now use 54 kWh batteries[1], though power output is limited to less than a Tesla Model 3.

Next year they’re supposed to increase power output to 350kW, which is comparable to a Model 3 Performance. Of course Formula E cars are much lighter, so acceleration and handling are far better than the Tesla sedan.

1. https://en.wikipedia.org/wiki/Spark_SRT05e

Why can't you brake aggressively with regenerative braking?

Cars can typically stop quite a bit faster than they can accelerate. This is especially true for two wheel drive cars because two wheel drive cars still have four wheel brakes.

To brake as fast as the traction limit on the tires, which is what you get from disc brakes, you would need four wheel drive and then bigger than normal electric motors and everything else to be able to absorb that much power that fast.

And then the battery would get really hot, especially if it was small.

I think at peak braking, a lot of energy is lost as heat as opposed to going back into the battery.

Perhaps battery sized for a reasonably long joyride and nothing more? I'd say that's how you'd build a lightweight electric sports car.

Yes, a small, fast charging lithium-carbon battery is how you build a lightweight scooter so why not a sports car:

https://www.mahle-powertrain.com/en/news-and-press/press-rel...

Or lithium-sulfur batteries for a battery pack that weighs less:

https://lyten.com/lyten-launches-lithium-sulfur-battery-plat...

Or just go for battery swaps:

https://www.gogoro.com/news/400k-gogoro-network-subscribers/

I was under the impression that smaller batteries had a limit to peak power draw. Perhaps not important if you have an ultra-light vehicle and you’re not attempting to build a competitor to the Plaid.

That's in line with the Lotus philosophy of light weight. A lighter battery doesn't need as much superstructure (the rest of the car) and doesn't need as much raw power to accelerate itself around.

Perhaps thermal management could be somewhat opened up to the driver with short "sprints" possible, to add some more driver involvement to the experience.

There must be a balance. The lighter the car, the more acceleration you get per watt.

I’d be very happy with a light weight EV Miata that went 0 to 100km/h in under or around 4 seconds. Not Model S Plaid or high end 911 fast, but still by far the fastest production Miata.

You'll love this then: https://youtu.be/VZws7kE3U5k (EV swapped Mazda Miata MX5).

There's a full build series too by the company that made it. I think £20k was mentioned as the cost of the conversion kit if they were to sell one. 120 miles range.

Cool, thanks. I'll check it out.

I've mostly been keeping an eye out on the aircooled VW conversions (or that EV 1968 Mustang on youtube).

It'll really get interesting when you see more from-scratch cars that don't have the ICE history built in. There are a lot of changes that could be made in design. If the government didn't love to get in your business so much, maybe there could be a world of street-legal EV karts.

There are - golf carts. They don't have the same sex appeal as a sports car, but in the many communities in the US where those are considered street legal, they are flourishing! They usually don't have doors and have a low top speed, but make for great third or fourth cars. Their top speed is low and limited by the law, though the laws that I've seen only specify what the top speed (often 35mph) but not how long (or how quickly) it takes to get there.

Many are still on lead-acid batteries (36V or 48V) but you didn't specify battery chemistry. :)

It depends on the batteries. It's true that larger packs generally draw less current per cell; whether you can get away with a small pack depends on whether the cells are designed to handle high discharge rates without damage.

Tesla's approach seems to be to optimize their cells for energy density rather than power density. They can do that because the packs they use are huge. On the other hand you have relatively small batteries that go in hybrids that are optimized for power density.

That makes sense.

I keep wondering why we haven't seen an EV Miata, but you'd probably end up with a small, 4000lb car.

Lacking significant battery improvements, I'm thinking the electric F150 is going to be the game changer in all this.

Have you forgotten the original Tesla Roadster? The Miata occupies a very specific niche (there are other sports cars, but none with the same balance of affordability and performance and availability as the Mazda Miata), but there are quite a few EV sports cars. They're just not remotely humanly affordable.

Interestingly enough, the Roadster is based on a Lotus Elise, so we've come a full circle here..

A lot of people want electric Miatas. I think the main reasons they aren't being made is that Mazda would have to invest a lot of R&D into designing it and they're a relatively small car company that can't do everything and they're probably not convinced that they can make an EV that feels like a Miata.

The main issue is batteries. They could either make a light EV without much range, or make a long-range EV that's quite heavy. Placement's an issue too. If they put the batteries in back under the trunk, they'll have too much weight in the rear causing it to spin out on corners. If they put it under the middle of the car like in most modern EVs, it'll make the car taller and look very un-Miata like. Best case is probably to put most of the battery in the front where the engine was, but I suppose that might be a safety issue (it could be crushed in a collision).

I think an electric Miata will happen eventually, but probably not until Mazda can buy cells that are in the 250-300 watt hours per kg range.

(Personally I would love to see an EV Miata with a manual transmission, but that's probably not going to happen.)

I don’t understand why you’d buy an automatic miata, let alone an electric one. Is there even a market for this?

Because it fits other parameters of practicality. Gatekeeping what's a real sports car might fly on car enthusiast forums, but it just isn't a good look outside of them (it's not a good look there either, tbh).

Mazda sells a decent number of automatic Mazdas each year (24% of softtops, 48% of hardtops in 2018-2019 according to auto blog), so people are buying them. The reason to buy a hypothetical electric Miata? Same as for any sports car - it's faster than yours, or at least as fast I can afford.

Whether there's a market for them, I can't say, but if someone doesn't understand the existing market for an existing car, I'm extremely doubtful of their predictions about a hypothetical new car in that niche.

Miatas are completely impractical cars. Have you actually driven one?

Of course it comes down to personal taste, but I can’t understand why you’d buy a “fun car” but strip away all the things that make it fun. There are much better alternatives at that point.

I’d buy a small electric sports car because of the high acceleration. I drove manual transmissions all my life and, while it’s fun in a race course, it’s far less entertaining in traffic.

Gas-powered cars are annoying to drive in traffic because the engine has a minimum RPM. EVs don't have that, so in stop-and-go traffic you'd be able to just leave it in 2nd gear the whole time and never touch the clutch.

Technically there's no reason an EV Miata couldn't have a manual transmission, it's just that auto manufacturers so far have largely decided they'd rather just opt for a more powerful motor than deal with the drive train complexity, weight, and friction losses of a transmission.

I don't expect Mazda to make a manual transmission EV Miata but it's something they could do if they really wanted to.

I thought a valuable experience in driving a fun car would go missing when going to an electric. Not so. Driving a fast, well handling electric is pure joy to me.

Fine. We'll design a control system for EVs where you can feel that a fake clutch actually does something. We can supply speakers and a simulated tach to give the full sports car experience.

Really my own guess is that the manual trans will continue on the way out due to emissions law if nothing else (and lack of interest). Modern cars have little visceral interest in any case, probably better to buy a hemicuda with a stick or a Cobra kit.

"utilizing the vehicle structure as the battery enclosure" is more commonly described (by Tesla at least) as a structural battery, i.e. utilizing the battery enclosure as an integral part of the chassis.

This is what scares me about electric cars. This type of design seems more likely to mean disposable cars. This is the automotive equivalent of a glued in non serviceable battery in a phone.

From an environmental standpoint this seems like a step backwards. It can be cost effective to replace entire damaged engines and transmissions even in older vehicles. People are keeping cars for longer, currently the average is over 8 years.

There are many motorcycles with the motor as a structural component. It does not mean you throw away the bike instead of repairing or replacing the motor.

There's a big wikipedia article on the various vehicle frame technologies thru the ages.

https://en.wikipedia.org/wiki/Vehicle_frame

So my commuter car is a cheapie Yaris ICE not EV. Its lead acid battery lives on a shelf attached to the frame, kind like a body on frame by analogy, except instead of bolting a car body to the frame they're bolting a battery shelf to the frame. If they ripped out the battery shelf and embedded a shelf directly into the front quarter panel of the body, then theoretically the car would be a little lighter. Its probably not worth it for a small lightweight lead acid battery. Giant EV battery, on the other hand 5% lighter might be a lot of weight...

Maybe a more intuitive way to understand the difference between a unibody type design and a body on frame design, is to look at old pickup trucks and you can rip the pickup bed off the frame and the truck works fine because the wheels and brakes and all the parts attach to a frame, so a bed-less pickup truck is just a pickup truck without a bed. Now if you rip off the back of a unibody car the entire back of the car would literally disappear because there is no frame, the frame is the body. Like the suspension parts attach to the body. There is no separate body and frame, there's just "the back of the car".

So one way to build a EV is to convert an existing chassis by bolting big battery pack "boxes" onto the frame. There exists a frame of a car and you bolted boxes of batteries to it as an addon. But a lighter way, which takes a lot more engineering, is building the battery "boxes" into the frame itself; there is no separate battery box there's a compartment in the frame that holds the batteries. You can't replace the battery "box" or the frame separately because they are not separate they are the same piece of metal. Much more engineering, much lighter.

I would imagine you can replace the batteries just as easily in a unibody EV as a body-on-frame EV. But you can't replace the rusted out battery box on a unibody EV because there is no separate battery box, its engineered into the frame.

The biggest disadvantage of unibody designs is everything is embedded in everything else so in a body on frame car a minor fender bender you remove and replace part of the body. But with a unibody the whole suspension and drive train gotta go too. To replace EV battery in a body on frame design you simply remove the battery from the frame. In a unibody system there might be a lot more labor hours maybe you gotta remove all the wheels and doors and seats to yank out a substantial chunk of the middle of the car.

An average EV will last longer than 8 years. Early fears of battery longevity proved to be unfounded.

Ideally the whole car collapses simultaneously.

Agree that this article really didn't deliver on its headline, as we're still in the dark about how the measures mentioned will lead to lightweighting (not that they won't do it, just the article doesn't deliver).

The first thing that concerns me about this layout is that it looks like the "Chest Layout" with the batteries mid-mounted in that tall trapezoidal shape will significantly raise the center of mass. I've found that this almost inevitably results in worse handling performance, unless offset. Of course, if this somehow achieves far lighter overall weight than a "Skateboard" layout, it could still be a winning design (but we don't know that yet).

It might be lightweight compared to the Teslas of the world, Evija is only a smidge over 1600kg .. heavy compared to the Elises but light compared to the other ev-players .. who knows, I'm going to buy one anyhow :). Want to order the Emira but Sweden is quickly going down the path of taxing the hell out of all new ICE cars.

1600kg is not very lightweight in the EV world. It's 100kg more than an old Nissan Leaf or Renault Zoé, which are very common in Europe. The old first gen BMW i3 weighs 1200kg. For sure it's not the same performances but weight didn't seem to be the main focus for this Lotus.

So a Zoe is 1570kg and has a tiny engine and 50kw battery :) not sure it's comparable with something that's has 4 motors, 2000hp and a 70kw battery :) The battery alone on the evija is 680kg and probably very different just to be able to get the amp up enough to power the massive engines and spike output when needed.

An old Lotus Elise was all about the weight, not power. They didn't follow this concept with the Evija, with so much power requiring a huge and heavy battery pack.

Agree, owned an Lotus Elise, truly amazing driving car but bad at everything else. Creating an electric car at 900kg is just not possible today even with just 250hk. With all new regulatory requirements like all cars need autobreak and other active safety features I'm not sure a new Elise would be possible, I think that's why the new Emira focus on beings a good all around sports car instead of weight.

Agree. The thing you sort of hint at but don't specifically call out is that using the chest configuration gives it a shorter wheelbase, which means less chassis, body, etc weight than the skateboard design. It's still going to weigh a lot, but it will be less than many other EVs (of similar battery/ motor size).

It is not clear to me how putting the batteries behind the riders rather than under them makes for a shorter wheelbase. The article mentions a lower height, which presumably reduces aerodynamic drag, all else being equal.

Maybe it is a matter of getting a good compromise between wheelbase, drag and center of gravity height?

Update - more on that here:

https://arstechnica.com/cars/2021/09/heres-how-lotus-is-goin...

My understanding is that the skateboard would have to be too thick to fit within the shorter wheelbase, substantially raising the occupants, etc. I think this also plays into the chassis design since they say they can build the "chest" design as part of the chassis. I think the skateboard requires more of a traditional body on frame. This is sort of a guess though, but slightly based off of the explanation of how they designed the chassis of the C7 Corvette to be light and more rigid.

Edit: thanks for the additional link

You want a low center of gravity but also weight in the center of the 4 wheels of car, that's why most sports cars nowadays are 'mid-engine'. Weight in the center helps in turns since the car wants to rotate around itself.

Smaller moment of inertia at the same weight.

> The article mentions a lower height

There’s also an emotional component in the difference in perception of driving at 250 Km/h on a BMW 750 or in a Lotus where your seat is hugging the road under you.

Lotus has a history of producing extremely lightweight sport cars, see Lotus Seven [1], famously featured in the opening sequence of "The Prisoner" TV series.

[1]: https://en.m.wikipedia.org/wiki/Lotus_Seven

Don't forget their involvement with the original Tesla Roadster. Lotus was Teslas original contract manufacturer for their cars, back in the day, and helped out Tesla with some engineering and design resources.

https://www.tesla.com/blog/lotus-position

Yes, the founder of Lotus, Colin Chapmann, had this egineering philosophy regarding racing cars: "Every part's weight is something I have to carry. If a part doesn't even exist, it doesn't have any weight." (Paraphrased by me.)

The biography "Colin Chapman The man and his cars" by Jerry Crombac is the got to read for this topic. BTW., Crombac is a legend in sports journalism in his own right.

and at a time nobody even did care for aerodynamics of a cars underbelly [its ventro-basal anatomy, so to speak] Chapman aimed to optimize on a level known only from constructing air-planes. shark-skin'ish foils, if not mistaken, they too were among the first testing on racing cars

> famously featured in the opening sequence of "The Prisoner" TV series.

Not just featuring in the opening sequence, but indeed symbolic of the entire show. A quirky, agile stand-out from the crowd that represents freedom and individuality, yet in the end is still imprisoned to follow the same roads as everybody else.