Aboard a sailboat, electricity is the most important resource other than wind. Deep-cycle lead-acid batteries have been the gold standard for boats for ages. Recently though, a new type of battery has become increasingly attractive to voyagers: the lithium-ion battery.
Lead-acid batteries, of course, have been around for over 100 years. Different iterations of lead-acid chemistry have been developed, such as wet cell (flooded), gel cell and absorbed glass mat (AGM).
The wet cell comes in both serviceable and maintenance-free formats. Both are filled with liquid electrolyte and are basically the same, except maintenance-free units are designed for a specific life span, after which they should be replaced. These are more typically used as starting batteries in cars and boats. Serviceable flooded cells are typically used as “deep-cycle” batteries that are built with more robust internal plates that can withstand the physical stresses of being heavily discharged and then recharged. The gel-cell and the AGM batteries are specialty batteries that typically cost twice as much as a premium wet cell. However, they store very well and do not tend to sulfate or degrade as easily as wet-cell units. There is little chance of a hydrogen gas explosion or corrosion when using these batteries; they are the safest lead-acid batteries you can use. Gel cell and some AGM batteries may require a special charging rate.
Recently, a new type of battery that uses a different battery chemistry, the lithium-ion battery, has evolved and found its way to the marine marketplace.
Bruce Schwab, a former global ocean racer and a distributor for Lithionics batteries, commented on the rise of the lithium-ion battery: “Over the last decade or so, the advent of powerful yet safe lithium energy storage systems has greatly changed the cruising lifestyle. Faster recharging times, more voltage stability under high load, and no need for long absorption charge cycles are all major advantages over lead-acid batteries. The top lithium brands (not all!) have worked out batteries that can be safely integrated with powerful charging and load systems. The greatly reduced engine or generator running time saves fuel, extends engine/generator lifespan and allows more quiet time when away from the dock.”
Most everything on a sailboat runs off the battery bank, not only while anchored out but also while sailing with the engines off. Having a sufficient battery bank to supply those power needs is important. Having all the fancy electronics in the world on your boat won’t matter if you are not able to power them. “Previously, it was unheard of to be able to run HVAC for an entire night off battery power and recharge in an hour or so the next morning,” Schwab said. “Now, you can.”
Lithium batteries are expensive when compared to lead-acid. But in demanding applications (like on a boat), it is reported the high initial cost will be more than compensated for by longer service life, superior reliability and excellent efficiency.
Lithium is less than half the weight of lead acid and takes up a lot less space per useable amp-hour (Ah). This means more battery in less space and the reduction in weight can result in increased speed. Another strong draw is that lithium requires no maintenance.
Making the switch to lithium-ion is a good time to re-evaluate your entire battery/electrical system setup, a process that — depending on your technical knowledge — may require consultation with marine professionals. “Note that the change to a comprehensive and safe lithium system often necessitates a fair bit of use analysis, system design/layout time and other associated hardware upgrades,” Schwab said. “However, most boats preparing for cruising would need to do many of the upgrades anyhow, even if sticking with lead acid. Either way, it is important to work with an experienced marine electrician or facility when implementing powerful charging and energy storage systems.”
A lithium-ion battery installation behind a boat’s settee.
Courtesy Bruce Schwab/Lithionics
One last thing to consider when looking into batteries is international support. You do not want to end up with an issue somewhere across the globe and not be able to get service or warranty. If you are planning on serious cruising, support availability needs to be a factor when choosing battery type.
Your needs for electricity will determine the size, sophistication and cost of the batteries and battery management system you purchase. Here is a look at some of the major providers of lithium-ion marine batteries and the scope of their offerings:
RELiON provides a complete line of 12-, 24- and 48-volt batteries for marine use. From the RB50 (12V, 50 Ah, 14.8 pounds) that reportedly maintains consistent power and comes equipped with a built-in battery management system (BMS) and M8 terminal type, to the far more sophisticated RB48V300 (51.2V, 300 Ah, 388 pounds). According to the company, this model also maintains consistent power and has built-in overcharge protection.
Mastervolt is a brand sailors are likely aware of. The power systems company offers a comprehensive line of lithium-ion batteries. Its most basic marine offering is the MLI-E (12V, 90 Ah, 27.6 pounds) with M8 terminals and integrated monitoring. The MLI Ultra 24/5000 (26.4V, 180 Ah, 128 pounds) is its largest and top performance battery. It boasts integrated BMS (including monitoring for amp-hours consumed and state of charge), as well as a series connection capability of up to 10 batteries.
Victron Energy offers lithium-ion units with integrated cell balancing. Batteries can be both paralleled and series connected. The cell balancing/monitoring cables can be daisy-chained and must be connected to a BMS. A Bluetooth app is available to monitor cell voltage and temperature.
Lithionics Battery’s NeverDie BMS with OptoLoop technology makes it possible for one external BMS to monitor multiple batteries, either in series or parallel connection. This creates a flexible system design that gives you the option to expand battery capacity in the future with the company’s parallel combiner box. The Lithionics Plug & Play system lets you start with just one battery module and plug in additional battery modules as needed. The NeverDie BMS is equipped with protective safety features, as well as battery status and state-of-charge monitoring, and comes standard on all Lithionics Battery systems. According to its website, Lithionics uses “heavy-duty contactors for BMS on/off switching controlled by a custom microprocessor.” The company also offers an optional Bluetooth transmitter on its NeverDie BMS, so you can monitor battery voltage, state of charge, temperature, current and status code remotely from your mobile device.
No matter the manufacturer you choose, you need to do your research to determine what capacities you will need for your specific situation. Building an electrical system for your vessel is a good place to reach out for professional assistance to assure that you have ample power in a safe manner when at sea or ashore.
Charlie Humphries is an ON staff member and an experienced sailor with more than 40,000 offshore miles.