MARINE ELECTRICAL INVERTERS &
LITHIUM BATTERIES

MARINE ELECTRICAL INVERTERS &

LITHIUM BATTERIES INSTALLATION

Lithium Batteries and Inverters for Boats

Lithium battery technology has transformed marine electrical systems. Advances in battery technology, originally driven in part by the electric vehicle industry, have made marine lithium batteries and LiFePO4 battery systems increasingly practical for boats.

When paired with a properly sized marine inverter, lithium batteries can provide enough stored energy to operate air conditioning, appliances, electronics, and other AC equipment while at anchor. For some boats, this can significantly reduce generator use and make extended periods of off-grid boating possible.

LiFePO4 Marine Batteries

“Lithium battery” is a general term that describes several different lithium battery chemistries. The type most commonly used in modern marine applications is lithium iron phosphate, or LiFePO4.

LiFePO4 is different from the lithium-ion battery chemistry commonly associated with consumer electronics. LiFePO4 batteries are well suited to marine applications because they offer high usable capacity, long cycle life, and excellent thermal stability when properly designed and installed.

Another important part of a marine lithium battery is the Battery Management System (BMS). The BMS continuously monitors and manages the battery, including charging, discharging, cell voltage, temperature, and other operating conditions. Depending on the battery design, the BMS can disconnect the battery when it reaches a specified limit or when a fault condition such as over-temperature, over-voltage, or under-voltage occurs.

Many modern marine lithium batteries also include communication capabilities such as Bluetooth, Wi-Fi, CAN bus, or other digital interfaces. These systems can provide detailed information about the battery, including charging and discharge rates, state of charge, estimated time remaining, cell voltages, temperatures, and fault conditions. Some systems even allow the battery to be remotely enabled or disabled.

Higher-Voltage Lithium Batteries for Trolling Motors

Another advantage of lithium battery technology is the availability of higher-voltage battery configurations. While traditional marine batteries are commonly used in 12V systems, lithium batteries can be configured into 24V, 36V, and other higher-voltage systems.

This makes LiFePO4 batteries an excellent choice for high-voltage electric trolling motors. A 24V or 36V lithium battery system can provide the voltage required by modern trolling motors while delivering substantially more usable energy than a comparable lead-acid battery bank.

For example, a trolling motor designed for a 36V system may require three 12V lead-acid batteries connected in series. A properly designed 36V LiFePO4 trolling motor battery system can provide the required voltage while significantly reducing battery weight and often providing more usable capacity.

Higher-voltage lithium systems can also reduce the amount of current required for a given amount of power. This can be particularly beneficial with high-output trolling motors, where lower current can mean smaller conductors, lower voltage drop, and improved electrical efficiency when the system is properly designed.

When upgrading a trolling motor to lithium, the battery voltage, BMS capabilities, charger, wiring, overcurrent protection, and trolling motor manufacturer's requirements all need to be considered. Not every lithium battery is suitable for series connection, and some manufacturers specifically require batteries designed to operate together in higher-voltage configurations.

For fishing boats using 24V or 36V trolling motors, lithium battery technology can provide a significant improvement in weight, usable capacity, and overall performance compared with traditional lead-acid battery banks.

How Much More Usable Capacity Does Lithium Provide?

One of the biggest advantages of LiFePO4 batteries is their greater usable capacity compared with traditional lead-acid batteries.

For example, a 110Ah AGM battery is generally limited to approximately 50% depth of discharge if long service life is a priority. That provides roughly 55Ah of usable capacity.

A properly designed 110Ah LiFePO4 battery can typically provide substantially more of its rated capacity for normal use. This means a lithium battery with the same 110Ah rating can provide considerably more usable energy than a similarly rated AGM battery.

LiFePO4 batteries can also provide thousands of cycles when properly charged, discharged, and maintained. Actual service life depends on the battery manufacturer, installation, operating conditions, depth of discharge, temperature, and charging practices.

Marine Lithium Battery Installation Requires More Than Replacing the Batteries

Although LiFePO4 batteries can be an excellent upgrade, a marine lithium battery conversion is not simply a matter of removing the old batteries and installing new ones.

Lithium batteries have different charging requirements and operating characteristics than traditional lead-acid batteries. The entire charging system needs to be evaluated before making the conversion.

This may include:

Battery chargers
Alternators
Solar charge controllers
Inverter/chargers
Battery monitoring systems
Battery Management Systems (BMS)
DC distribution and overcurrent protection
Battery isolation and disconnects
Engine-starting requirements
Communication between charging and monitoring equipment

For example, an alternator connected directly to a large lithium battery bank can be subjected to substantially different operating conditions than when charging a lead-acid battery. Alternator protection and appropriate charging controls may therefore be required.

Solar charge controllers and battery chargers also need to be configured for the specific lithium battery manufacturer's charging requirements.

Marine lithium battery installations should also follow applicable ABYC standards, manufacturer requirements, and appropriate overcurrent and disconnect protection.

Marine Inverters

A marine inverter converts DC power stored in the boat's batteries into AC power, typically 120V and, on some boats, 240V split-phase power. This allows equipment such as air conditioning, refrigerators, microwave ovens, televisions, household appliances, and other AC loads to operate without shore power or a running generator.

Inverters are not new technology, but modern marine inverter/chargers are considerably more sophisticated than earlier systems. Today's equipment can combine several functions into one system, including:

DC-to-AC power conversion
Battery charging
Automatic transfer between shore power, generator, and inverter power
Battery monitoring
Programmable charging profiles
AC and DC voltage monitoring
Alarm and fault monitoring
Generator control
Remote monitoring and control

Many modern marine inverter/chargers can also communicate with other components of the boat's electrical system. Depending on the manufacturer and equipment, the system may be monitored through a dedicated display, multifunction display (MFD), Bluetooth, Wi-Fi, Ethernet, or a marine digital network.

Choosing the Right Inverter for a Boat

Every marine inverter installation is different. The correct inverter depends on several factors, including the boat's AC loads, battery-bank voltage and capacity, available installation space, electrical service configuration, and whether the boat uses 120V, 240V, or 120/240V split-phase power.

The inverter must also be properly matched to the battery bank and the boat's existing AC and DC electrical systems.

An inverter that is too small may not be able to start or operate larger loads such as air-conditioning compressors. An inverter that is unnecessarily large can add cost, installation complexity, and significant DC current requirements.

Lithium Battery Conversions for Boats

When we install LiFePO4 batteries, a marine inverter/charger, and the supporting charging and monitoring equipment, we often refer to the project as a lithium battery conversion.

Adding solar charging can make the system even more capable. A properly designed combination of LiFePO4 batteries, inverter/charger, solar charging, and energy monitoring can dramatically reduce generator run time and allow a boat to spend more time away from shore power.

For boat owners who frequently anchor out, cruise off-grid, or want to minimize generator use, a lithium conversion can be a major upgrade to the boat's electrical system.

Marine Lithium Battery and Inverter Installation

At Maritec Marine LLC, we specialize in marine electrical systems, lithium battery conversions, inverter installations, charging systems, and troubleshooting. We evaluate the boat's existing electrical system and design the installation around the vessel's actual power requirements rather than simply replacing individual components.

Our technicians have experience integrating LiFePO4 battery systems, marine inverter/chargers, alternator charging, solar systems, battery monitoring, and digital marine networks. We have also applied this experience to RV electrical systems.

If you're considering upgrading your boat to lithium batteries, adding an inverter, reducing generator use, or creating a more capable off-grid electrical system, Maritec Marine LLC can evaluate your existing system and help design the right solution for your boat.

MARINE ELECTRICAL INVERTERS & LITHIUM BATTERIES