Solid Improvements
Solid state batteries further propel an electrified future.
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Most boats carry the energy they need as liquid petroleum and then employ engines for propulsion and powering equipment. That’s changing: Lithium batteries paired with inverters, for instance, often now augment or replace generators. Power per pound still favors diesel fuel for the foreseeable future, but compared to conventional lithium, new solid-state batteries store nearly twice the energy per pound in significantly less space, and provide four-fold faster charge and discharge rates. These advantages power applications where lead-acid and even standard lithium struggle.
To be clear, solid-state batteries still store energy utilizing lithium, but thin coatings replace liquid chemical electrolyte within each cell. The technology has actually been around for about two decades, mostly in medical and military applications, but it’s been difficult to produce. “It wasn’t a technology problem, it was a scale problem,” says Tom Calef, founder and CEO of Solid State Marine. “How do you make that nano-thickness coating the same every time, over hundreds of thousands of cells, and make it financially attainable to a broad market?”
With that hurdle passed (Calef won’t tell me quite how), his company now offers solid-state batteries at competitive prices in voltages and sizes common for marine applications. Besides reducing battery size and weight, replacing wet electrolyte with ultra-thin coatings decreases resistance, so solid-state batteries transfer more power with less heat.
Real-world examples highlight those benefits. In an electric-powered fiberglass replica of a classic mahogany speedboat, Elco’s EP-250 inboard motor draws 130 kilowatts from Solid State Marine batteries to push the 20-foot Lancer Craft to just over 30 knots. “The [wet-cell lithium] batteries on the market couldn’t sustain that continuous draw,” says Dean Heinemann, Elco’s general manager. As battery voltage dropped, so did output, decreasing speed and range. “Switching to solid state gives us the power we need through the entire range of stated battery kilowatt hours.”
Of course cutting battery weight in half helps, too. The Lancer Craft’s electric propulsion package weighs 1,043 pounds—about 100 pounds lighter than the V8 engine and fuel system in Lancer Craft’s conventionally powered boat. Wet-electrolyte lithium batteries would increase that by 800 pounds—like carrying a spare gas engine. “That extra weight in the motor compartment makes it hard to get the boat to plane,” Heinemann says. Weight also robs performance and range. Using solid-state batteries, the boat planes quickly, travels more than an hour at cruising speed and runs for days at displacement speed. That’s plenty for many lake boaters.
Saltwater boaters see practical gains, too. Tristan Raynes’ charter boat, a 32-foot SeaVee, was originally equipped as a megayacht tender with a Seakeeper 2. He recently replaced its three dedicated 12-volt lead-acid batteries with a single solid-state battery. “I used to leave the engines running just to use the Seakeeper,” Raynes says. “Now I can go out on any trip—six or eight hours, moon tide, blowing 30 knots—and shut down the engines. I have yet to see that battery drop below 40 percent.”
Raynes saw similar improvement for the Minn Kota trolling motor that keeps Ohana over stripers or blackfish in strong Rhode Island currents. Three wet-cell lithium batteries occasionally ran dead on blustery days. Now a single 36-volt solid-state battery takes up one-third the space, cuts weight by half, and provides 20 percent more power. “I still have a wreck anchor on the boat, but I haven’t used it since changing batteries,” Raynes says.
Lifespan of Calef’s batteries mirrors traditional lithium, he says, retaining 95-percent capacity after 1,500 cycles—a full discharge every day for four years. Capacity drops to 75 percent sometime after 2,500 total cycles. But that’s based on 100-percent discharge, not the 80 percent typically specified by the manufacturer.
Safety is enhanced, too. A pierced wet lithium battery oozes electrolyte that electrically shorts and overheats those cells, potentially causing a thermal chain reaction. Solid electrolyte won’t leak, avoiding the short. And even when testing worst-case failures, Calef says, his batteries don’t heat past 50 degrees Celsius (122 Fahrenheit)—not hot enough to start a fire.
Still, Murphy’s Law suggests caution. Reputable manufacturers employ quality battery management systems that disengage when electrical systems go wrong. Properly sealed components preclude mixing saltwater with lithium, which creates hydrogen gas. But Murphy plagues mechanical systems, too. Turbocharger fires, seawater hose failures, leaky fuel tanks that store far more energy than batteries—at least for now—all present risks we mitigate. Simpler, battery-powered systems might resolve problems in the end.
