eBay Find: Walter Kern’s Electric-Powered 1974 Saab Sonett III

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Walter Kern was something of a legend in Saab circles. He built the series of Quantum race cars in the late 1950s and early 1960s that broadened Saab’s racing appeal beyond rallying. He was also an engineer with IBM and an inveterate tinkerer. He converted this 1974 Saab Sonett III to run on electric power all the way back when it was new. It’s now for sale on eBay.

If you look back at the history of Volkswagen, Mercedes-Benz, Porsche and BMW, it took the understanding of people in America like Max Hoffman to sell those odd, unlikely cars to Americans. The same thing was going on at Saab. It was building its weird little automobiles to satisfy people in Europe, but the big market was in the United States. Bob Sinclair figured out that Saabs would be appealing to the same kind of people who were buying Volkswagens in the late 1950s, and eventually forced Saab’s hand to build cars like the Saab 900 Convertible specifically to please American tastes.


At the same time Sinclair was essentially selling Saabs door-to-door in the 1950s, Walter Kern was taking Saabs racing. Kern built five Quantum cars between 1959 and 1962. They took what Kern felt were solid mechanical components and made them look and handle as well as any small sports cars of the era.

Walter Kern trained as a nuclear physicist at MIT. In the early 1950s — like a lot of incredibly smart people trained at the universities in Boston and Cambridge — he got interested in sports car racing, and made regular trips to wring out early sports cars at Thompson Speedway in Connecticut.

Kern Quantum Thompson Speedway

He realized early on that his Fiat-powered Siata and an early Porsche were starving for oil in the corners, and engine failure was the result. He was drawn to Saab’s two-stroke engines to solve the issue. According to Bruce Turk at the Albany Saab Shop, “He decided to design and build his own car, incorporating the Saab power plant. Walter worked with Al Conrod of Itek Corporation and Jack Soumala of the MIT instruments lab on an IBM computer to design a chassis with neutral steering.”


The Quantum I was built in 1959, with a computer-desinged chassis that Kern engineered in his spare time at IBM. According to Turk, “Walter told me that he believed his was the first car to have its chassis designed entirely by computer (remember this was around 50 years ago!) The computer he used filled an entire room.”

His Quantum I raced at Thompson Speedway in May of 1960 and took a first place in its class.


While the Quantum I and II were both prototype race cars, Kern’s Quantum III had production aspirations. He presented the car in 1962. Kern managed to build two of the cars and presented them at the New York International Auto Show. Saab suggested that it was going to build the cars, but they never went into production.


His Quantum IV was designed as a kit car for the SCCA Formula S series. He built one Quantum V in 1965 with a Ginetta body.

In the early 1960s, both Björn Karlström, an aircraft and automotive illustrator, and Walter Kern were independently building Saab sports cars. Instead of going into production with either of the prototypes developed by independents, Saab showed two prototypes, one of which eventually became the Saab Sonett III.

Kern loved the car, and during the first and second fuel crises, he also loved the idea of a small, agile sports car like the Sonett powered entirely by electricity. He developed this electric-powered Sonett III along with Dave Hosmer. Kern drove the car daily until he was almost 80 years old.


Old Saabs take particularly well to electric conversions because of their free-wheeling clutch design, a holdover from the time when Saabs had the two-stroke engines that Kern liked so much. Because two-stroke engines rely on a fuel-oil mixture to lubricate the engine, they’re dependent on a constant flow of fuel. When a driver takes his foot off the gas, the throttle closes, and if the car is allowed to engine-brake, it can cause catastrophic engine failure.

Saab’s solution was the free-wheeling clutch, which operates the way your multi-gear bicycle does when you stop pedaling. It offers no engine braking, but it keeps the engine running at idle while the car is coasting. The free-wheeling clutch is operated via a lever that can also allow engine braking.


In its Kern/Hosmer iteration, it had an 86V electric system, supplied by 14 Trojan T-145 batteries, three in the front, and 11 in the back. Each battery weighed 72 lbs each, for a total payload of 1,008 lbs of lead-acid storage. The car had a seven-inch GE motor, a toothed belt driving the original alternator to keep the 12V system charged, and two on-board chargers. It also had a Curtis 72-120V, 350A controller, which it still has today.


When Max Hall — the current owner — purchased the car in 2010, he modernized the electrical system quite a bit to get it to the current state-of-the-electric-car art. It now sports four fewer 12v batteries, each of which weighs 12 pounds less than the original batteries, for a total battery payload 400 pounds lighter than Kern’s design. An Advanced DC 4001 motor replaced the little GE, and gives the Sonett III better performance and a much higher top speed.



Instead of the original alternator to supply the 12V system, Hall replaced it with an ElCon DC-DC converter, replacing the dual chargers with a new ElCon charger at the same time. The motor is now air-cooled thanks to a blower motor from a Dodge Caravan, and the 350A Curtis controller benefits from a heat sink and a cooling fan.

Today, it can travel at “faster than 65 mph,” according to Hall. He reports it having plenty more power to go faster, but he’s never taken it up to its maximum. Current range is somewhere between 30 and 50 miles, depending on how it’s driven. Hall uses the car once a week to commute to the private school where he’s a physics teacher.

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Along with the car, the winning bidder gets a Tyvek car cover, and the domain for the car’s website at saab-e.com.


Antiques Roadshow always talks about how items that appeal to more than one interest group make the most money. Unfortunately the overlap of this 1974 Saab Sonett III’s Venn Diagram is where Saab enthusiasts and electric car builders meet — a pretty narrow sliver of the vintage car market — but it’s a super cool piece of Saab history nonetheless. It was so well regarded that it was invited to take part in 2012’s Boston Cup concours event on Boston Common. 

Craig Fitzgerald

Craig Fitzgerald

Writer, editor, lousy guitar player, dad. Content Marketing and Publication Manager at BestRide.com.