Lithium Batteries: Are They Safe?

Lithium Batteries: Are They Safe?

Recent fires are making some boat owners wonder if replacing their batteries with lithiums is worth the risk.

Recent fires are making some boat owners wonder if replacing their batteries with lithiums is worth the risk.

On September 15, 2022, an unoccupied Tesla caught fire while parked at a Chinese restaurant about a mile and a half from my home in Stamford, CT. I could see the smoke from my balcony. The fire department spent 42 minutes extinguishing the flames, using three hoses discharging 200 gpm each. That’s about the same volume of water normally used to quench a fully engulfed multi-story home. No one was injured.

Early in November, 2022, a lithium-ion battery (LIB) in an electric bicycle caught fire on the 20th floor of a luxury high-rise apartment building in New York City; more than three dozen people were injured. An E-bike caused another fire in a Bronx apartment building at the end of November, injuring three people. According to a FDNY spokesman, nearly 200 fires in New York City were caused by this type of battery in 2022, resulting in at least six deaths and 140 injuries.

In March, 2022, the 650-foot cargo vessel Felicity Ace sank after burning, adrift and unmanned, for almost two weeks. Her cargo was 3,828 luxury automobiles, many of them electric (EVs), worth an estimated $400 million; they’re now sitting on the bottom of the ocean about 100 miles from the Azores. (So that’s where my Lamborghini is!) Some reports suggest the fire started in a LIB in one of the electric vehicles. Several cargo ships have been damaged or destroyed by fires caused by LIBs. In June, 2020, for example, lithium-ion batteries aboard the car carrier Hoegh Xiamen caught fire at dockside in Jacksonville, FL, and burned for eight days before fire crews were able to extinguish it.

The 134-foot motoryacht Kanga, the 115-foot Siempre and the 88-foot Pesa were all destroyed by fire in the past few years. All three fires were blamed on the lithium-ion batteries powering electric surfboards, water scooters and other toys. Spend some time searching the internet, and you’ll find more instances of LIBs causing destructive fires on both land and sea. Does this mean that folks who have swapped their lead-acid batteries for LIBs, which can pack more energy into the same space as traditional batteries, and at less weight, are now sailing on potential fire ships?

Enumerating fires caused by LIBs as I’ve done above isn’t the kind of reporting that will get me admitted to the Columbia School of Journalism: I failed to mention fires during the same period that weren’t caused by lithium-ion batteries. Cars with gas engines can catch fire, too—with far higher frequency; fire often breaks out aboard cargo ships for many reasons; and boats without LIBs on board still burn from electrical or fuel fires. Lead-acid batteries can explode if mistreated (and off-gas hydrogen while charging). E-bike fires? Well, you can blame those on LIBs; old-fashioned pedal bikes don’t catch fire very often.

Nor did I mention the gazillion rechargeable LIBs around the world that didn’t ignite over the past few years. Lithium-ion batteries are statistically very safe. So why do some catch fire? Most fires result from one of a handful of causes: manufacturing defects in the battery; damage to the battery; or improper charging—using the wrong charger, usually to speed up recharging, can overheat the battery to the point that one or more cells ignites. The battery-management system (BMS), either built into the battery or a standalone model, should shut down charging before this happens, but it’s not foolproof. Once the battery overheats, the failure can be self-sustaining. Battery folks call this “thermal runaway,” and once it starts, you’re S.O.L. unless you have the expertise and equipment to extinguish a runaway LIB.

The best way to protect yourself, and your property, is to buy high-quality lithium-ion batteries and correctly matched chargers, whether to power an E-toy or provide DC juice for your boat. El Cheapo batteries often have substandard components haphazardly assembled—manufacturing defects can guarantee battery problems down the road. Add an equally poor quality charger and you’re literally playing with fire. Store removable batteries in a location that’s neither too hot nor too cold, ideally in a fireproof safety bag; they should be recharged in the bag, too. Read and follow the manufacturer’s recommendations when you buy and use a LIB.

A damaged LIB should be replaced ASAP—the internal separator membranes between the electrodes are just thick enough to insulate, but thin enough to let ions pass through. Damage to the exterior of the battery can damage these membranes, resulting in what most of us think of as a short circuit. This generates intense heat and, very often, ignition—the thermal runaway mentioned above. The battery-management system can’t help with this situation, either—the battery must be cooled down by external methods, e.g., torrents of water, or allowed to burn until all its copious energy is exhausted, ideally without setting anything else alight. Reportedly, LIBs used to power E-water toys aboard Kanga were leaking a brown liquid before the fire broke out; the crew were making arrangements with the manufacturer to replace them, but apparently thermal runaway beat them to it.

All LIBs Are Not Alike

When sensible skippers replace their lead-acid batteries with LIBs, or order a new boat with a powerful array of LIBs rather than a genset, they choose lithium-iron-phosphate (LFP or LiFePO4) batteries, one of six types of LIB on the market today. (Some experts consider LFPs not to be lithium-ion batteries, maybe to differentiate them from more volatile LIBs. But LFPs also rely on lithium ions’ ability to release and retrieve electrons to produce energy and be recharged.) LFP batteries combine a cathode of lithium iron phosphate with a graphite anode, swimming in an electrolyte composed of lithium salts. They are the most stable LIB, but can store only about half the energy pound-for-pound as, say, the LIBs used in EVs. That isn’t so critical for boat use, since there’s always a source of charging available—start the engine or plug in the yellow cord.

Note that none of the conflagrations mentioned above was caused by LFPs. Quality LFPs for marine service are built tough enough to withstand the pounding and vibration typical aboard a powerboat. Professional test labs have managed to coax them into thermal runaway, but it takes a lot of doing; some manufacturers claim you can drill holes in them and they won’t ignite. (Search the ‘net for more on this.) They are the safest LIB you can buy, and I wouldn’t hesitate to be shipmates with a professionally installed and properly monitored and maintained array of high-quality LFPs—the humming of gensets in a quiet anchorage drives me insane. Really, the danger comes from the batteries in electric water toys and other appliances.

When maximum energy storage, light weight and compact size are important, as they are in EVs, E-bikes, E-surfboards, E-cigarettes, laptops, tablets and so forth, manufacturers choose LIBs with cathodes of lithium combined with some combination of manganese, cobalt, nickel, aluminum oxide and/or titanate (titanium oxide). These metals are much more volatile than the good old iron in LFP’s, and will ignite at a much lower temperature. Add this natural volatility to the typical misuse that these batteries endure in the E-world, throw in some salt water and corrosive sea air, and it’s more likely that one of these damaged LIBs will fire off.

Even a small LIB that catches fire can lead to catastrophe—there are lots of flammable materials aboard the typical boat, and once they’re ignited, for any reason, you have your hands full. If you carry electric water toys on board, you might have some of these batteries stowed in a locker—with a fire alarm. I recommend sending the E-toys ashore and giving your kids kayaks and paddles; it’ll be safer and they’ll get some exercise. At the very least, invest in fireproof bags to store the batteries; they don’t cost much—way less than a fire.

What about the batteries in electric boats and outboard motors? E-boats have similar requirements to EVs, and often carry similar, non-LFP, batteries. Hinckley’s Dasher, for example, is powered by two lithium-ion batteries originally designed for BMW’s i3 EV. Hinckley says the batteries are waterproof, with “efficient cooling and temperature distribution with compact size and superior shock resistance.” Torqeedo uses BMW-designed LIBs in their electric outboards, both lithium-iron-phosphate and lithium nickel manganese cobalt oxide—the LIB chemistry used in EVs. If you’re considering an E-boat, and you’re worried about the LIBs running amok, check the battery chemistry and do your research before writing the check.

What Do Experts Say?

What do experts think about the wisdom, or lack of, of installing lithium-ion batteries to power DC circuits? It depends on which experts you ask: The LFP batteries that replace lead-acids are a lot more stable, say the pro-lithium crowd; no worries about carrying them on board.

The anti-lithium folks say, basically, “Why risk it?” Lead-acid batteries have done the job for more than 160 years (Gaston Planté invented the rechargeable lead-acid battery in 1860), they are safe and affordable and, when treated correctly, have a long life. Why rock the boat with expensive lithium batteries? Makes sense to me, unless you specifically need to carry maximum stored DC juice and minimize recharging with the engine or generator. Otherwise, I’d stick to lead-acid, too. (You can start a heated discussion anywhere boat owners gather by extolling the pros or cons of lithium-ion batteries.)

What about your insurance company? What do they think? Insurers like nothing better than to charge higher premiums, and given their risk-averse nature, I think soon they’ll be asking if you carry lithiums aboard your boat, and I guarantee if your answer is yes, it’ll cost you more money. Some insurance companies are doing this already, either refusing to insure boats with LIBs aboard, or putting a cap on paying claims. This is a growing issue not only in the U.S. but in Europe and Australia as well. To be safe, consult with your insurance broker before switching to LIBs.

And, again, be very careful how you carry, store and use non-LFP lithium-ion batteries. Don’t let an E-toy battery land you in a feature story in marine—or on social—media.

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This article originally appeared in the March 2023 issue of Power & Motoryacht magazine.


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