Emergent Technologies, Evolving Hazards
New Lithium-Ion Batteries Pack A Lot of Energy. Here's Why That Could Be A Problem On BoatsPublished: January 2012
Boatbuilders have long been obsessed with shaving weight to improve efficiency and boost speed, especially when it comes to high-tech professional racing sailboats. So it's no surprise that the Volvo Ocean Race team Emirates New Zealand opted for the latest, greatest, and lightest in marine batteries when they installed Mastervolt MLI 24/160 lithiumions (commonly called Li-ion) in their boat, Camper. That produced a battery weight reduction of about 70 percent, though at a retail cost of tens of thousands of dollars. As the technology matures and costs drop, however, the batteries we see on high-tech boats like Camper today will trickle down to recreational boats like ours, tomorrow. Unfortunately, a lack of knowledge about these batteries could also cause a trickle-down of new dangers.
When Li-ions first appeared on boats, they presented a significant risk. "We had one in Playstation [the Maxi-cat that set a trans-Atlantic speed record in 2001] and it caused a serious fire," said Tom Weaver, owner of Eastport Yachts and managing partner of Weaver-Price Design & Construction. "The weight advantage was huge, but when charging, the lithium-ions were super-volatile."
And while this technology has certainly become better in recent years, some danger remains. According to Ed Sherman, the author of Advanced Marine Electrics and Electronics Troubleshooting, "It's still the Wild West out there when it comes to lithium-ion systems. Thank goodness we have these cutting-edge sailboat racers who can act as early adopters, and help work the bugs out. But the technology is still so new and it's moving so fast, that even in some well-engineered systems, there have been unexpected issues."
Batteries, like these conversional wet-cells, have always had the potential to start fires due to their high energy content. These caught fire when an errant wrench contacted both terminals (Claim #0205712). Newer technology batteries with higher capacities and less forgiving charging characteristics will require even more caution along with sophisticated monitoring.
All Juiced Up
Of course, battery fires have always been a hazard on boats. But as the nature of batteries evolves, the nature of the threat evolves as well. The key to keeping this hazard in check? Understanding these changes.
In the past few years, numerous examples of computer and cell phone battery fires resulting in mass recalls have shared one thing in common: Whether it's a wafer-thin half-ounce power cell or a 400-pound behemoth of a car battery, Lithium-ion has been the culprit. But Li-ions have a long list of significant advantages over traditional batteries—they're lighter; they hold their charge better; can handle more charge/discharge cycles; and don't have charge-memory problems. These advantages are significant, especially when you compare hard numbers. A Li-ion has the ability to store up to between 125 and 180 watt-hours per kg of battery, while an average NiMH (nickel-metal hydride) battery can store closer to 100 watt-hours per kg and a common lead-acid battery stores less than half that amount. Unfortunately, since Li-ion batteries represent the latest technology has to offer, we haven't necessarily figured out the best and safest ways to store the punch that they pack.
The basic way these batteries work is the same as traditional batteries: Electrons move across an electrolyte, between an anode and a cathode, to create a flow of electricity. Since lithium is a highly-reactive alkali metal, it's possible to cram more energy into a smaller space. All that power, however, tends to cause overheating in certain circumstances. Insulating membranes and built-in circuits can prevent it, but subtle manufacturing defects or battery damage can be problematic.
"We really need to start thinking about Li-ions as systems," Sherman explained, "not just as batteries we use and then recharge with a charger. They need to be controlled and managed precisely, because failure is always a possibility with any series of circuits. And in this case, there's a lot of power to deal with."
The American Boat and Yacht Council's vice president and technical director, John Adey, agrees. "The amp rates can be enormous, and the cells in Li-ions need to be equally charged and monitored for temperature and equalization. So you really need a high-end monitoring system," he said.
If Li-ions are dangerous, why haven't we heard more about high-tech battery fires on boats in specific? For the most part, because so few are currently in marine use. In fact, Weaver is one of the few boatbuilder/ designers around with extensive Li-ion experience going back over more than a decade. And in his opinion, even today, Li-ions are still too dangerous for recreational boating use. "For a professional racing sailboat saving 10 pounds is like the holy grail, much less saving 100," he said. "But I've seen boats on fire because of them and I wouldn't even consider putting one on a recreational boat just yet. Even when we use them for dayracing, we actually keep the batteries on a separate boat, and run them out just before the beginning of the race."
As the expense drops and technology advances, however, the popularity of Li-ions is sure to grow in the recreational marine marketplace. And that means boaters need to get ahead of the curve. Fortunately, organizations like ABYC are already on the job. "We're laying the groundwork for new battery system standards now," Adey said. "We'll have them done by July, and they should be out by the following July."
As both Sherman and Adey point out, using the latest and most advanced monitoring systems is a big part of reducing the danger of Li-ions. These systems include microprocessors which can "talk" with the battery to vary the charge characteristics from start to finish, as well as providing over-current protection. Merely hook up your Li-ion to a standard marine battery charger which blindly pumps out juice, and you'd be asking for trouble.
Unfortunately, this isn't where battery charger problems end as they relate to onboard fires. We want our power and we want it fast, and regardless of battery type, that translates into higher amperage demands. Simple single-stage bulk chargers are available these days all the way up to 50 or more amps. That's a lot of power, and trying to cram it quickly into a battery of any sort doesn't work very well because batteries don't charge in a linear fashion. When they're fully or mostly discharged they can accept a charge quickly, but as they become closer and closer to fully charged, they accept less and less juice. That's why "smart" multi-stage chargers, which sense the battery's state and reduce charge accordingly, are far less likely to cause problems.
Just what exactly happens inside a battery, if a not-so-smart and all-too-potent charger is used to jam power into it? It can overheat and explode, or it can cause venting. Since the gas that escapes from a lead-acid battery is hydrogen (a small amount of which is created when charging most batteries, hence the constant need for good ventilation), this can create a major hazard. Hydrogen gas is extremely explosive, and can be set aflame by electrical accessories other than the battery and charger if it gathers in an area that's not 100-percent spark-protected.
Worse yet, in the case of a Li-ion battery, venting can occur in the form of open flames. Li-ions become more unstable when overcharged because the lithium forms a metal plating on the anode, while the cathode becomes an oxidizing agent and produces carbon dioxide, increasing pressures inside the battery cells. If the charging continues, eventually the battery will release that pressure—period.
The likelihood of encountering these types of problems on boats grows as we grow our own desire for power. In the past five to 10 years, larger electric outboard and inboard propulsion systems, the use of more inverter-driven onboard accessories, and generally increased electrical demands has expanded our use of larger and more potent battery banks. Couple these needs with the newer and less thoroughly vetted technologies, and it's easy to see why fire concerns are growing, rather than shrinking. Today those concerns may be focused on
tricked-out competition sailboats like Camper and Playstation. But tomorrow, there's a good chance they'll apply to the object of your own obsession,
To comment on this article, please contact Seaworthy@BoatUS.com.
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Few Li-ion batteries are designed specifically for the marine world, but Mastervolt has entered the market with the MLI 12/320 and 24/160 (www.mastervolt.com). These offer space and weight reductions of 70 percent, triple the lifespan of a lead-acid battery, and faster charging. Introduced in 2010 the MLI garnered significant attention in the industry, winning the Pittman innovation award presented by Sail Magazine as well as an IBEX Innovation Award. Most experts agree that, when combined with Mastervolt's management systems with MasterBus CANBus battery/charger communications, it represents the best technology available on the market today. Unfortunately, this new technology does not come cheap—a single battery and management system can retail for well over $6,000.
Another manufacturer of cutting-edge batteries designed for marine use is an Australian company called Aquawatt (www.aquawatt.at/en). This company introduced a lithium battery this year, along with what may be the world's biggest electric outboard, a 30-hp powerplant. Aquawatt says their lithium yttrium phosphate design is safer than standard Li-ions, but we haven't seen these particular batteries in action just yet. Aquawatt doesn't have an American distributor at the time of this printing but they hope to have one by the end of 2012, so you should look for this technology to hit our shores in the very near future.