Lithium-ion batteries are often the best, albeit most expensive, solution for boating applications, such as powering trolling motors. They’re also often the best power source for the ever-growing number of electric propulsion systems.
As an example, Boston Whaler recently launched its 360 Outrage with the Fathom e-Power System, which uses a bank of lithium-ion batteries to eliminate the need for a noisy gas or diesel generator onboard. Sweet dreams.
Here’s a look at why that builder and others are moving toward greater use of lithium-ion batteries.
Pros and Cons
Conventional lead-acid, deep-cycle batteries age relatively rapidly if they’re routinely depleted past the 50 percent threshold. Lithium-iron-phosphate (LiFePO4 or LFP) batteries can be depleted 100 percent without seriously affecting battery lifespan. They also don’t suffer consequences from being routinely charged to 100 percent instead of the recommended 90 percent for lithium-cobalt-nickel batteries.
Most major manufacturers of portable marine batteries have settled on cathodes made of lithium-iron-phosphate for several reasons. Unlike other types of lithium batteries, these have a much lower risk of thermal runaway — a chain reaction that happens when a lithium battery gets too hot. These batteries also don’t use cobalt and nickel, ingredients that are expensive, difficult to source and less environmentally friendly than iron-phosphate.
Still, a few quirks need handling, particularly with charging and cell management. New generations of “smart” LFP batteries have battery management systems with integrated computer chips designed to get the most life out of the battery. Some models can transmit battery data via Bluetooth to portable devices or multifunction displays.
Although some battery manufacturers, such as Dakota Lithium, offer dual-purpose LFP batteries that can be used for starting, some engine manufacturers, such as Yamaha Marine, don’t allow them as primary starting batteries on gas-powered outboards because of “safety concerns and inconsistencies of lithium battery products.” In addition, Yamaha’s battery management system is only set up for lead-acid batteries, so even LFP house batteries aren’t sanctioned.
Lightweight, Intelligent Power
The newest member of the Mastervolt battery family is the MLI Ultra 1250, a lithium-ion, 12-volt, 100-amp-hour battery that weighs only 33 pounds. It has a battery management system that performs several duties designed to extend longevity and deliver maximum power. (Mastervolt is part of Brunswick’s Advanced Systems Group.)
The Mastervolt battery management system optimizes the use of each of its cells. Its self-learning, balancing algorithm can predict the behavior of each battery cell and balance each cell proactively, resulting in a faster, more efficient charge cycle that can be completed in 60 minutes.
The MLI Ultra 1250 also has a physical on/off switch and an integrated battery safety switch that automatically disconnects the cells in case of an emergency. And although few people go boating in arctic conditions, the unit comes with an integrated thermal heat-pad and low-temperature control to ensure maximum charging performance at freezing temperatures.
To take the guesswork out of setting up the charger, there’s an integrated battery switch and plug-and-play capability. The installer wires the MLI Ultra 1250 to any supported Mastervolt charger, then connects the communication cable. The battery will automatically configure the charger.
Although it is possible to use a conventional charger with LFP batteries, using one as part of an installation runs the risk of cell-killing overcharges. Considering the expense of LFP batteries, it makes sense to use a lithium-ion-ready charger such as NOCO’s Genius GenPro10X4, which is an on-board, four-bank, 10-amp-per-battery charger with selectable modes that can handle lithium-ion and all types of lead-acid batteries at the same time.
The NOCO Genius is compact, can be submerged for hours, and has a host of features that make its use nearly foolproof, thanks to warning lights that let the user know if he has hooked up the battery incorrectly, or has selected an incorrect charging mode. This product will alert the user if a battery is damaged, and will shift into standby mode if the battery voltage is too low to detect. A thermal sensor optimizes the charge to match the ambient temperature.
Forget everything you learned about storing lead-acid batteries for the winter, such as making sure there’s a full charge that should be periodically trickle-charged. None of that applies to LFP batteries.
Ideally, LFP marine batteries should be stored with around a 50 percent state of charge because the internal electrodes of a fully charged battery age faster. They’re more chemically active, which is why most LFP batteries are shipped with as little as a 20 percent state of charge. A disconnected LFP battery loses only about 1 percent to 2 percent of its charge a month, so it can go for quite a while before being fully depleted.
According to manufacturers such as Dakota Lithium, the best practice when recharging for the new season is to charge each battery separately, to match the voltage of each before connecting them into a series. If you charge them all at once, when one battery gets to 100 percent, the charging stops — even though the other batteries might only be charged to 80 percent. For users who boat year-round, this procedure, known as balancing the batteries, should be done at least once a year.
Though they’re quite expensive today, lithium-ion batteries are being installed by OEMs at ever-increasing rates. These batteries are reliabile, durabile and efficient. They have become so good, in fact, that we can now envision a generator-free future in the boating space.
This article was originally published in the May 2022 issue.