Alerion’s take on electric drive utilizes the most up-to-date technology available. It involves a 7.5kw AC motor, powered by a pair of 160amp 12V DC lithium iron phosphate batteries from Mastervolt. These batteries, the first developed for the marine market, won a 2010 Freeman K. Pittman Innovation Award from SAIL. They have three times the cycle capacity of a lead-acid battery, and can be discharged by 80 percent without damage.
Lithium iron phosphate is safer than other lithium ion chemical combinations because it won’t catch fire, a recurring problem with some Li-Ion batteries—remember all the laptop battery recalls of the last few years? (To get an idea of the potential dangers of runaway batteries, check out Nigel Calder’s column in the June issue of SAIL.) The Mastervolt batteries have integral management systems designed to bring them up to charge as quickly and efficiently as possible, in conjunction with a charger that’s optimized for these batteries and can be programmed to make the most of differing shore power situations.
This system was commissioned by the boat’s owner, who sails in British Columbia, and was put together by the engineers at Alerion and Mastervolt. It was a treat to lift the engine cover and see not the usual diesel engine lurking in its cave, but a neat and tidy electric motor driving a folding propeller via a shaft and stuffing box. The batteries are installed under the cockpit seats just abaft the bulkhead, and the charger is housed between them. There’s no fuel tank, no filters to look after, no impeller to fret about, no dipstick to check, no alternator belts that need constant adjustment. Best of all, there’s no whiff of diesel fuel.
Alerion’s Scott Bryant switched on the motor (literally) and juggled the forward-neutral-reverse gear lever/throttle to ease the Alerion out of its slip, with only the faintest of hums from the motor. The silence was almost uncanny as we glided out of the marina. The throttle (rheostat?) was set up to operate just like that on a diesel-powered boat, though a volume-control knob would have worked just as well.
The motor has plenty of torque; the boat crash-stopped quickly and accelerated briskly enough to spill your coffee. There was no vibration from the motor, and at low speed, had it not been for the forward motion you’d not have known the motor was even running. There was slightly more noise at higher speeds, much of it from the water gurgling at the transom. Cruising speed is 6 to 7 knots, at which rate the batteries are expected to last for three or four hours before it’s time to plug them in for a recharge. That’s a range of, say, 24 miles, more if you’re running at low speed. When you think about the amount of time you typically have your engine running when you’re daysailing, this should be ample. There is also the potential for some power regeneration from a spinning prop when the boat is under sail, but it will take some finesse to get this working with a folding prop.
Apart from the turbulence from the prop when accelerating hard and a whine emanating from the sterngland, silence reigned supreme. And that, after all, is part of the grand appeal of sailing.
An installation like this is maybe 50 percent more expensive than a diesel engine with its associated hardware, but when you factor in the almost non-existent maintenance costs of the electric drive, it’s not at all a bad deal if you intend to keep the boat for a few years. Electric drive is still in its infancy, and as motors become more efficient and the cost of batteries comes down, so the pricing will become more competitive. In a way, early adopters like the Alerion’s owner, Vincent Argilo, are investing in the technology’s development.
But hey, never mind the money – just savor the sound of silence.