Kriss Motors Electric Conversions

Ezra Dyer Sonett review

In the mainstream car market, electric vehicles are defined on one end by eco-mobiles like the Nissan Leaf and the other by the luxury performance cars like the Tesla Model S and upcoming Mercedes-Benz SLS AMG E-Cell. As for used cars, there’s really not much to choose from, since the modern electric renaissance is still only a few years old.

But in a smattering of garages around the country, dedicated tinkers are reimagining classic sports cars and mating electric power with vintage aesthetics.

For instance, what would a Saab Sonett have been like if lithium batteries were around in 1969? Kriss Motors decided to find out.

The Sonett’s stock V4 got hoisted, replaced by an 80-hp electric motor and a 12.5 kW lithium iron phosphate (LiFePO4) battery pack that provides around 70 miles of range. The Sonett’s column-mounted manual transmission remains.

“Because the power and rpm range match the original engine pretty closely, you can retain the stock transmission,” Eric Kriss of Kriss Motors says. You might shift gears less often than you would in an original Sonett, though, since the electric motor’s 110 lb-ft of torque is available from zero to about 4,000 rpm.

Dash with digital gauges

The result is a smooth, quiet, deceptively punchy Sonett. I’ll admit that I’ve never ridden in a stock, internal-combustion Sonett, but I doubt that the original powertrain would offer the effortless fourth-gear surge of torque that allows Kriss’ screaming-blue Saab to knife through the chaos of suburban Boston traffic.

It’s not overpowered, by any means, but electric propulsion seems to suit this car. “Lightweight sports cars with relatively modest power are ideal for electric conversions,” Kriss says. Since you’re not looking for a three-second 0-60 time, you can use light-duty components and retain the stock transmissions. Another Kriss Motors electric car, a replica Porsche 356 Speedster, also uses a manual transmission. That car carries a stouter, 23.8 kW battery pack that’s good for 140 miles or so.

Electric Saab Sonett

Front bay with battery pack
Cars like the Sonett become ever more esoteric with each passing year, with parts increasingly hard to find, leading Kriss to predict that electric conversions might soon become an accepted alternative to an engine rebuild or replacement. As for the heresy of re-powering a classic car using a high-performance golf cart motor and a bundle of Chinese submarine batteries, Kriss says the reactions vary.

“The Porsche people can be skeptical,” he says. “The Saab crowd generally thinks it’s cool.”

    -- Ezra Dyer - August 13, 2013

The Cars

Porsche 356 Speedster

The iconic Porsche Speedster proved to be an excellent EV conversion candidate due to its low weight, relatively simple design, and ample front/rear compartments for mounting pristmatic lithium battery cells. Weight distribution was improved over the original rear engine configuration with better acceleration and overall performance.

Saab Sonett

The unusual fiberglass Sonett, originally powered by a Ford V4 engine, combines a low center of gravity and front wheel drive, optimal for our high performance EV conversion. Without the need to accomodate a long drive train, the space behind the two seats was used for additional batteries. The original four-speed transmission remains intact along with the braking system.