Batteries aboard today’s saltwater fishing boats prove more critical than ever, relied upon to power an ever-growing number of onboard systems, as well as starting the main engines.
While marine batteries have morphed into a wide range of types, sizes and applications, most still rely on the same lead-acid chemistry invented more than 160 years ago. Today, however, advanced lithium-iron-phosphate (LiFePO4) battery chemistry provides boating anglers with greater electrical power, and your next new boat may well be equipped with this revolutionary new technology.
Marine lithium batteries offer amazing advantages, but they also require new thinking when it comes to cost, installation, applications and charging. Let’s look at how these jibe with saltwater fishing boats.
Deep-Cycle vs. Starting
Most marine lithium batteries are designed to serve in deep-cycle applications, not as starting batteries. Marine starting batteries are purpose-built to crank engines, for the most part, using lead-acid technology, which is good for short bursts of high energy. Most lithium batteries are not designed to produce these kinds of high-energy electrical bursts, but rather lower levels of energy over long periods. So, with a few exceptions, lithiums are relegated to the role of deep-cycle-house and trolling-motor batteries.
Lithium batteries also might damage marine engines if employed in starting applications. And engine alternators can’t produce the special charging profiles that lithium batteries require (more on this later), which means that it is a good idea to completely isolate these new-age batteries from the engine starting circuit.
Run Times
Unlike deep-cycle lead-acid batteries that taper off in power delivery and go dead at about 50 percent capacity, a lithium battery delivers full power for nearly its entire discharge cycle. If you’re running an electric trolling motor with lead-acid batteries, the power will gradually fade after a few hours and the motor will lose its initial oomph. With a comparable lithium battery, however, the motor will pull strong for nearly its entire discharge cycle.
Weight Comparison
The most obvious difference between lead-acid and LiFePO4 batteries is weight. For example, a 31-series lead-acid deep-cycle battery that offers 105 amp-hours weighs around 60 pounds, while an X2Power SLIL31-125DC-BT 12-volt deep-cycle battery that provides 125 amp-hours weighs just 33.6 pounds. This can make an even bigger difference if, for example, you’re assembling a bank of three 12-volt batteries for a 36-volt saltwater trolling motor—that’s 180 pounds for the three lead-acid batteries versus 101 pounds for the three lithiums.
Weight savings can become even more remarkable because many companies offer single lithium batteries in 24, 36 and even 48 volts, as well as 12 volts. A case in point is the Dakota Lithium 36-volt 100-amp-hour battery that weighs just 32 pounds, saving 148 pounds when it replaces three lead-acid 12-volt batteries.
Life Expectancy
Lithium batteries offer as much as 10 times more battery life than lead-acid systems, some providing up to 4,000 cycles versus 400 cycles for a comparable AGM (absorbed glass mat) lead-acid battery. On the other hand, lithium batteries are more expensive. The X2Power SLIL31-125DC-BT, for example, currently retails for $599.99. Compare that to a Duracell Ultra 31-series 12-volt, 105-amp-hour lead-acid AGM battery, which retails for about $319.99. Yet, with the greater longevity of lithiums, they pencil out as better long-term buys.
Charge Times
Don’t try using a conventional charger on a lithium battery; LiFePO4 chemistry requires a special charging profile to bring it back to full capacity safely and without damaging the battery. Many lithium brands offer compatible chargers as accessories, and buying a new charger can run up the cost of switching to lithium. That said, a LiFePO4 battery charges four times faster than a comparable AGM lead-acid model.
Monitoring Methods
Because lithium batteries provide full power throughout the discharge curve and stop cold once out of juice, boating anglers need a reliable method for monitoring the state of charge. Many LiFePO4 models resolve this with a built-in Bluetooth monitor that connects to an app on your mobile device to keep you informed about available power. There are also aftermarket monitoring systems that connect to the battery and display the state of charge and other parameters.
With lithium batteries of the past, there were concerns about flammability. However, those have largely dissipated with the advent of reliable LiFePO4 cobalt-free technology. Marine lithiums provide many benefits to boating anglers in proper applications. At the same time, lead-acid batteries—particularly today’s AGM models—still have a place aboard today’s saltwater fishing boats, especially when used for starting engines.
