Larger new cruising yachts, especially those at the quality end of the market, have been routinely fitted with lithium boat batteries for the past few years. Arcona, for instance, says up to 90% of their larger yachts now leave the factory equipped with them. Equally, the technology is increasingly embraced in the racing world, whether at the top end on IMOCA 60s and Fast 40s, or smaller IRC yachts competing in RORC’s offshore races. Benefits include a huge reduction in physical size and weight, along with a radically increased number of charge-discharge cycles. Typically the best lithium boat batteries will withstand four or five times the number of cycles compared to most deep cycling lead acid batteries. This is a significant factor in reducing their long-term costs, although it has to be remembered savings will often not be realised until five years after installation, when conventional boat batteries may be nearing the end of their lifespan. As prices of lithium ion relative to capacity continue to fall, total life cycle costs are likely to drop below those of lead acid batteries. However, a lithium boat battery is not a straightforward drop-in replacement for lead-acid batteries. Instead, a comprehensive and unified upgrade of boat battery management systems and regulation for all charging sources is needed to eliminate the possibility of thermal runaway creating a self-sustaining fire.  Despite the improving economic case for lithium boat batteries, this is rarely the prime driving force behind owners’ motivation. Quite simply they are better suited to today’s increasingly complex and power-hungry yachts. Lithium boat batteries can even make it possible to run air conditioning through the night without resorting to the disruption of a generator. Equally, a lithium-based system may be able to store enough power to make it feasible to change from gas to electric induction cooking, and from a petrol tender to an electrically powered one.  Article continues below… Each of these changes have safety benefits in that they get rid of other sources of potential fire or explosion. However, there is so much power concentrated in a lithium boat battery that its chemistry is more lively than that of conventional batteries, with a potential thermal runaway situation able to create a self-sustaining fire that’s impossible to control.  Granted, this is an extraordinarily unlikely event, but boats have been lost as a result and multiple safeguards are essential. Safe systems A properly designed installation will have three comprehensive lines of defence against thermal runaway. At the heart of the system the individual cells of each battery have electronics to keep the state of charge balanced across adjacent cells and to trigger isolation of the cell in the event of an over-temperature situation.  At the next level up each battery module also has a more sophisticated embedded battery management system that can also shut the unit down. Both the cell level and battery level monitoring are, in theory, backstop solutions that should never need to be called upon.  Each battery module also communicates with … Continue reading Lithium boat batteries: Why now is the right time to upgrade your electrics