Race boats get an all-electric powertrain

Feb. 21, 2013
Mercedes-Benz and Cigarette Racing design an all-electric race boat.

Visitors to this year’s Miami International Boat Show are seeing a new kind of open-ocean racing boat, one powered by batteries and a dozen electric drives. The boat is collaboration between Mercedes AMG and Cigarette Racing, with Mercedes supplying the powertrain and Cigarette supplying one of its Top Gun Racing hulls. The result, the Cigarette AMG Electric Drive, boasts 2,220 hp and over 2,210 ft-lb of torque for a top speed over 100 mph.

The hull measures 37.5 ft long with an 8-ft beam and a static draft of 27 inches. Originally, the hull was outfitted with a pair of Mercury Racing 600 SCi inboard engines that could team up to generate 1,200 hp, enough to easily push it past 100 mph.

The electric drives were lifted from a Mercedes SLS AMG Coupe, a gullwing coupe introduced at last year’s Paris Motor Show. A compact, permanent-magnet, synchronous 185-hp motor is attached to each wheel and 1,208-lb of lithium batteries is tucked away inside the chassis. The coupe accelerates from 0 to 62 mph in under four seconds and has a top speed of 155 mph.

For the boat, Mercedes and Cigarette engineers shoehorned in 12 electric motors, six per prop shaft. Each motor has its own inverter, and each set of six motors weighs 600 lb, which saves some weight compared to the 1,276-lb inboard they replace. But that weight savings was quickly lost when engineers had to add a liquid-cooled 4,840-lb battery pack. The 240 kWh pack consists of 3,456 lithium-ion cells that store power at 400 V. This gives the electric powertrain a maximum driving current of 6,000 A. The boat also carries a pair of chargers that put out 44 kW of power and can deliver a full charge in seven hours. The motors, chargers, battery pack, and power electronics were all borrowed from the SLS Coupe.

Engineers were able to mount the motors and battery pack low enough in the hull to lower its center gravity, making it a well-behaved emission-free fast boat.

At full power, the motors consume 2.4 MW, which means the battery can only provide full power for about 10 minutes. This makes the energy capacity of the battery pack equivalent to about 15 gallons of gas.


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