There’s nothing quite like the look of a classic Mustang, but for those of us who want a car that’s reliable and eco-friendly, an electric vehicle (EV) is the way to go. Sure, Ford has started making electric Mustangs, but they just don’t have the classic feel of a ‘65.

Good news, classic car owners—there’s now an easier way to turn your vintage ride into a modern, battery-powered vehicle. All it takes is some clever engineering.

Converting the Classics

For the right price, any car can be electrified. But a custom conversion can cost upwards of $70,000 and up to eighteen months of work. And lacking standardized components, systems, and processes, the reliability and safety of a converted EV could be called into question.

Chris Hazell thinks there’s a better way. The CEO of automotive startup Fellten, Hazell told engineering.com he hopes to make the EV conversion process quicker, safer, and more affordable. How? Instead of starting from square one with a custom conversion process, Fellten (Welsh for lightning) has developed bolt-in electric powertrain conversion kits for several classic cars.

“We want to bring about the rapid uptake of classic electric cars and enable other companies to do these conversions in a quick, safe manner,” Hazell says.

Fellten currently offers conversion kits for three classics: the Land Rover, Classic Mini, and Porsche 911. Each kit features the same technology and design, though with different physical form factors. Fellten provides the kits to automotive workshops and vehicle restoration facilities, and offers training and documentation so technicians can reliably perform the conversion. Hazell says that using standardized components in every kit helps to alleviate the supply-chain issues that seem to plague all manufacturers these days.

Engineering a Conversion Kit

So how does it all work? To design an EV conversion kit, Fellten starts by determining key specifications such as weight, performance, range, and charging speed of the EV-to-be. The vehicle’s weight is addressed first, since that dictates its range and that determines charging times. The body style affects performance; while engineers can slightly enhance the performance of a sporty model like a Porsche, souping up a Classic Mini could be dangerous. 

Fellten engineers conduct field and bench testing of the original vehicle, paying close attention to its acceleration, weight distribution, and handling. Then they remove the engine, transmission, and associated components and perform a series of 3D scans to determine the available space for the electrified powertrain. CAD engineers and structural engineers draw up a set of designs and layouts, a process that goes through multiple iterations. If any of the company’s pre-designed components fit, then they become part of the design.

The prototyping process starts with a test build of the battery box, followed by the wiring harnesses, low-voltage systems, and communication electronics. The electrical layout is redrawn with design software so the wiring can be mass produced. The software engineering team then programs the control algorithms to allow the powertrain to meet the vehicle requirements.

The engineers then move on to a complete system prototype, a “test mule” that’s taken on the road for longevity analysis. Inevitably, something breaks, leading to a design modification and another round of testing. This may continue for three or four iterations until the team decides that it’s good enough to release. Once it’s on the market, they’ll have additional data so they can modify the design for future models. Minor tweaks are made during the first year or so; when warranted, the team will release a new version.

Part of the engineering process includes design for manufacturability. While custom one-off retrofits are built entirely by professional engineers and technicians, these kits will be mass produced, so the designers ensure that they can be constructed by assembly-line workers using simple user guides.

Fellten says that its vehicles are “re-fitted to improve safety, handling, comfort, usability, performance, and sustainability.” The company will add regenerative braking systems, which increase vehicle range and improve braking ability, and replace the fuel gauge with a range prediction gauge that fits in the same spot. They can also add hill-hold and hill-descent modes to the braking system if desired. But they avoid adding features that significantly change the car’s original specs or its weight distribution. With such a small sample size, it’s difficult to predict how the vehicles will respond to changes in weight and performance.

About that Classic Mustang…

So what is Fellten’s long-range plan after classic car owners have all converted their darlings to EVs? Hazell told us that Fellten is following the Tesla model of starting out with low-volume, high-value vehicles, allowing the more affluent classic car owners to subsidize Fellten’s R&D, which will eventually lead to lower-cost, higher-volume models. (Mustangs, unfortunately, are not currently on the list.)

Hazell sees no future in EV conversion kits for “run-of-the-mill” vehicles. Classics, in spite of their high maintenance costs, are built to last; everyday cars are built to sell at a low price, which makes retrofitting them impractical. For the same money, a person could simply buy a new entry-level EV.

Many classic car owners are also gearheads who like to work on their own vehicles or, at a minimum, want to understand what’s under the hood. Fellten plans to appease these tinkerers by openly showing the technology, how it’s manufactured, and how it works. Since it’s not wise for amateurs to mess around with high-voltage systems, Fellten believes that the more the drivers know about how their electrified classics work, the less likely they are to open it up and try to find out for themselves.

But when has that ever stopped an engineer? (The only thing this engineer is missing is a Porsche 911.)