A recent post on EV Pulse broke the news that the Dodge Charger Daytona SRT concept car has a transmission and that future Dodge EVs will have “more than two speeds” transmissions. I know Tesla fans will immediately jump on this and point out that Tesla vehicles (especially the Plaid variants) are very fast and don’t have transmissions. So in this post I want to explain (again) why gearboxes actually make sense for EVs.
Before I get into the engineering of transmissions and why they are necessary, I want to point out that Stellantis (Dodge’s parent company) already sells at least one EV with a transmission. When I test drove the 2021 Jeep Wrangler 4xe, I figured out pretty quickly that it was using the transmission in EV mode even though there was no throttle.
If you’ve driven electric cars at all, you know that they have a lot of low-end torque, but that torque tends to drop off as the vehicle picks up speed. At some point the power is really low and may even hit a wall (either the speed limiter or the physical limits of the engine). Either way, the reduced acceleration power of an EV at higher speeds is usually noticeable and especially noticeable in the cheaper models.
In EV mode, she did the same thing 4x. I heard the familiar hum of the EV, felt the torque and felt it start to drop. But then something really cool happened: the vehicle shifted into second gear and the EV engine got a second wind. the familiar growl rose again, starting from a low pitch and rising as before. The vehicle did this twice more when it shifted gears under EV power.
While it’s hard to tell for a Jeep, it was pretty clear that the vehicle got better range as a result. Instead of having to sit at whatever rpm the engine needed to drive per minute, the 4x could select a gear for maximum range. Obviously, the small battery and inefficiency of the off-road-optimized Jeep Wrangler won’t give it amazing range, but it certainly performed better than it would have with a single gear.
Why electric cars with a transmission can get better performance and range
Unlike gas engines, electric motors can operate over a much wider RPM range. To avoid over revving the electric motor and destroying it like you would with a gas engine, electric cars only need one gear to cover all of its speeds. This means that the vehicles do not strictly require multiple gear ratios or a gearbox.
Even though an EV doesn’t need multiple gear ratios, Tesla has found a way to make the driving experience even better. At lower speeds, more power is sent to the rear wheels for launch purposes. At higher cruising speeds (motorway driving), power is sent mostly to the front engine, which has a higher gear ratio and thus acts as a second gear. Plus, because the front engine on the performance models is smaller and better suited for the job, it gets more power.
So while it would not be technically accurate to say that twin-engine Teslas have a transmission, it is correct to say that they have multiple gear ratios. So even the most die-hard Tesla Stan has to admit this is a good thing.
Porsche took things a step further by offering a two-speed gearbox in the rear drive unit. Both the front and rear drive units have a gear ratio of 8.5:1 at highway speeds, but the rear motor can go as high as 15:1, allowing for more torque multiplication during the initial launch before shifting into a higher gear than the Tesla. for highway driving.
The Taycan’s excellent results in Edmunds tests are mainly due to this, but also other elements. In its most efficient driving mode (which the EPA doesn’t use), it got significantly more real-world highway range than expected, while the Tesla fell short of the EPA’s expectations. But what happens when we go beyond 2 speeds? Would an electric vehicle benefit from 3, 4 or even 5 gears? The correct answer to this is “Yes”.
With lower gears for more torque at low speeds and higher gears for lower engine speeds at high speeds, both power and range should be seen in a big increase from the transmission.
But does it work in the real world?
For that I will have to direct the reader to the realm of EV transmissions. For decades before mass-produced electric cars were available, people in garages were converting their ICE (internal combustion engine) vehicles into electric cars. Most often they just bolted the electric motor onto the ICE car’s transmission because they didn’t have access to the transmission. We don’t have to ask if it would help because it has already been shown to provide all the theoretical benefits.
Want an extreme example? A Ferrari 308 that was converted to run on batteries after it was almost destroyed in a fire. To make this car electric, they added three motors that work together to drive a Porsche 4-speed manual transmission. (CleanTechnica reviewers called the car “scary” because it had such a ridiculous amount of low-end torque. But when you’re on the highway, the vehicle gets a decent range for what it is, just by shifting into a higher gear.
In addition, you don’t have to worry about the engine seizing because the electric motors don’t stop. If you are approaching a stop, just stop. There is no need to depress the clutch pedal, except when changing gears.
Here, too, automatic transmission technology can be useful. The great thing about using a manual transmission is that you don’t run into the problems that Tesla had with its failed two-speed project: you can turn off the power while shifting to avoid damaging the gears. The driver does this in the manual, but if you want to build your own automatic electric vehicle, a torque converter can just as easily soften the blow (although that would require a TCC system to lock that converter between shifts so you don’t lose range by slipping).
ZF’s transmission testing proved this the benefits are just as real for mass-produced EVs as they are for conversions. Not only did they increase the car’s range by 5%, but they also improved the acceleration values compared to the single-speed car. This allows the vehicle to bypass the trade-off between efficiency and performance, allowing for both. The ZF unit shifts gears at 70 km/h (just under 45 MPH). They also allow the car’s computer to control the powertrain and optimize gearing to better match the manufacturer’s goals (power, efficiency, towing, etc.).
In the end, it all comes back to price. For a cheaper car, which is mostly used in the city, one gear is enough. However, for a performance car or one that will be regularly driven at high speeds, it would make more sense to find ways to get a different gear ratio – and that’s exactly what Tesla did.
The “city only” era of electric vehicles will eventually come to an end as people want cars that can go more places. Customers will also continue to put pressure on companies to produce the types of vehicles they want. Manufacturers will use multi-speed transmissions to provide the performance that customers demand. And you will be very happy when they do!
With all of this in mind, I’d say for sure that Dodge is making the right call when they say they’re putting a transmission in their upcoming performance EVs.
Featured image provided by Dodge.
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