ILIOFOS Co.

Master these seven technical terms and you'll be your neighborhood's electric-boat guru.

Master these seven technical terms and you'll be your neighborhood's electric-boat guru. 

The world of maritime is being turned upside down by the onslaught of electric boats currently hitting the market. Internal-combustion-powered boats and vessels have been around for 140 years; they're old school and well understood. But the arrival of EBs and their new-school technologies has spawned an entirely new class of boating jargon. We want you to be fluent in it. We're here to help with this mini-glossary of seven EB tech terms. Master them and you'll sound smart—and be smart—about these newfangled battery-powered conveyances.

Motor Power

In North America many boatrmakers as also some of them in North Europe, quote the power of electric motors in horsepower, as they do for internal-combustion engines; however, motor power is also often expressed in kilowatts.

One kilowatt equals 1.34 horsepower. So if you see an EB motor that's rated in kW, add one-third to that number and you'll know almost exactly ow much horsepower it has.

Battery Capacity

The battery that powers an electric boat contains energy, which is measured in kilowatt-hours. If that unit sounds familiar, it's probably because it's the same one used by your utility provider to bill you for your home's electrical usage. For reference, one liter of gasoline contains 8.9 kWh of energy and a gasoline motor have a 30% efficiency, so from a liter of gas we gain only 2.67KWh .

Battery capacity in kWh is the time in hours over which a battery can output power in kilowatts. For instance, smaller EBs with 200 miles or so of range often have batteries of around 60 kWh. That means they can provide 30 kW (or about 40 horsepower) for two hours straight. That may not sound like a lot, but EBs traveling at a steady speed usually require just a fraction of that power, and some of the energy used to accelerate the boat and overcome hydrodynamic and sea-load drag can be recaptured through regenerative methods. There are two variations of battery capacity you may encounter: we quote "usable" capacity, the amount the boat can actually draw on, while some boatmakers quote total or "gross" capacity, which includes buffers that prevent the battery from discharging completely to zero.

Home-marina Charging

Today generaly, by far the majority of electric-boat miles come from batteries charged either at home or at marinas, depends from the type of motor (inboard or outboard) . There are two kinds of home charging. The first, called Level 1, uses a standard 120-volt wall outlet; the second, called Level 2, employs a more powerful 240-volt circuit akin to that required to run an electric stove or clothes dryer, and this is what we are using in Europe.

Owners who need to replenish more than 30 or 40 miles of range each day should install dedicated Level 2 charging equipment with its own charging cord in or on their garage. Level 2 systems generally recharge EB batteries about six to almost 20 times faster than a Level 1 hookup, depending on the output of the circuit and what the boat can accept. Those drivers covering fewer than 30 miles daily can get by using a 120-volt outlet and the portable 120-volt charging cord that comes with the boat. Some makers now provide charging cords with swappable pigtails that allow them to charge from both 120- and 240-volt outlets. Finally, public charging points, the kind you might encounter in a parking for boats or a marina, operated by networks, mostly charge at Level 2.

DC Fast Charging

While Level 1 or 2 charging uses alternating current (AC) from a building's electrical wiring, the quickest type of charging is known as DC fast charging. This is not something you would install at your house or an individual player at a marina; it's intended to support EBs for long-distance travel and is usually found at charging points in special marinas or near major ports.

Note also that fast charging is usually most productive between about 5 and 80 percent state of charge for the battery, because—like your mobile phone—the charging rate slows as the battery nears full, and juicing up that last 20 percent takes relatively much longer.

Charging Rate

The rate at which an EB can recharge is also measured in kilowatts. AC charging (Level 1 and Level 2) runs from about 1.0 to 19.2 kW, depending on what power level the boat's built-in electronics can accept and what the charging hardware can provide. DC fast-charging rates vary even more, from a now-obsolete standard of 24 kW to the fastest offered for passenger boats, which goes as high as 350 kW. The actual rate at which an EB charges always depends on battery energy remaining, battery temperature, and other factors.

The moral of the story is to know what rate your EB can take and match it to an appropriate charging station via the boat’s navigation system, where possible, or the various apps for route planning and charging-station location. .

From MPLe to MPKWe

Miles Per Liter Equivalent, or MPLe, is a measure of how far a boat can travel on the energy contained in one lt of gasoline. It's the EB efficiency measure cited by the EBA, intended to provide a comparison to how the agency rates the fuel-efficiency of fossil-fuel boats in mpg. For example the mpl number appears on the window sticker of a Car specification tables.

In practice, though, the most important EB metric for EB drivers is range: Can my boat take me to where I'm going and back on a single charge, given weather and speed conditions? When EB owners do discuss EB "efficiency," they actually tend to be talking about consumption—the rate of energy used when driving the boat - which is typically expressed in watt-hours per mile (Wh/mi) or its inverse miles per kilowatt-hour MPKWe (MPKWh or mi/kWh). True efficiency, which is what the EBA's MPKWe figures are, also includes charging losses and the inevitable battery drain that happens when the vehicle is parked. 

Bidirectional Charging

Also called "power out" or "boat to load" (B2L), bidirectional charging is shaping up as another selling point for EBs, one that most gasoline / diesel boats can't offer. It is the ability to export electricity from their battery packs via 240-volt outlets built into the boat. The power output is generally 1.9 to 9.6 kW.

These outlets can be used to operate anything from portable refrigerators or boomboxes, at beach events to power tools used onsite by construction crews. In this use, the EB stands in for a loud, exhaust-spewing gasoline generator. They can also be used to charge a stranded EB.

Some EBs can be used as generator replacements to power other boats or specific places near costs in the event of a blackout, after suitable hardware is added to the place's wiring. This capability was first demonstrated at electric vehicles in March 2011, after Japan's tsunami and nuclear catastrophe, when EVs were used to power medical equipment in field hospitals.