Long reserved for a few high-end or professional installations (blue-water sailing yachts, yachts, commercial vessels), lithium batteries have been developing since the 2010s aboard pleasure boats. But what does lithium actually provide compared to traditional batteries and what precautions does its installation require? Here is an analysis through the study of the advantages and limitations related to the LiFePO4 technology used for service batteries.
Traditional Marine Battery vs. Lithium: What are the Differences?
Recreational boats have always been fitted with lead-acid batteries derived from the automotive sector, first in liquid electrolyte versions and then in “maintenance-free” versions, GEL or AGM. Lithium batteries, for their part, are based on a different chemistry and on the presence of an integrated electronic management system, the BMS (Battery Management System, or battery management system).
More recent in the nautical sector, the lithium battery responds in particular to the increase in onboard electrical requirements, linked to the growing number of equipment, electronics, and comfort appliances.
Benefits of a marine lithium LiFePO4 battery
Among the advantages of a marine lithium battery, several points stand out, ranging from stored energy to rapid recharging, as well as lightness:
- Use of stored energy: a much larger share of stored energy can be used. Whereas the discharge of a lead-acid battery must remain limited in order to preserve its service life (it is strongly recommended not to discharge a lead-acid battery below 40 to 50%), a lithium battery makes it possible to use its full capacity.
- Weight and volume: a lithium battery for boats is lighter and less bulky. At equivalent capacity, its weight represents approximately one-third that of an AGM battery and two-thirds of its volume. This difference simplifies installation and can contribute to the performance of a sailboat or help reduce fuel consumption on a motorboat.
- Charge-discharge cycles: a lithium battery proves capable of withstanding a very large number of charge-discharge cycles. While traditional marine batteries generally withstand between 300 and 800 cycles, most lithium batteries accept between 2,000 and 5,000.
- Charging speed: lithium batteries accept much higher charging currents than lead-acid batteries. A lithium battery can thus be recharged approximately 5 times faster than a lead-acid bank of the same capacity, provided that sufficient charging power is available (shore power, generator, high-output engine alternator, etc.).
- BMS: the battery management system ensures its supervision by monitoring each individual cell to guarantee their balancing and therefore their service life. However, it also ensures that operating parameters remain within admissible values (high and low voltage, charge and discharge currents, temperature, etc.). As such, the BMS is capable of disconnecting the battery from the onboard electrical system if these conditions are no longer met.
Disadvantages of a Lithium Battery for Boats
Among the drawbacks associated with installing LiFePO4 service batteries on board, several points stand out, ranging from the need to check the charging chain to the often mandatory replacement of cables and protections.
- Charging chain verification: the transition to lithium requires verifying the entire charging chain, well beyond optimizing the existing system. Indeed, the differences in characteristics are such that the system’s operation, or even its safety, is at stake, for example, with the alternator which generally does not support a direct connection to a lithium battery. Furthermore, potential charge distributors often no longer perform their function. Not to mention the shore charger or the MPPT solar regulator (Maximum Power Point Tracking) whose charging profiles must be adjusted. While it is rarely necessary to replace everything, the charging infrastructure and the links with the other battery banks on board must be verified and generally adapted.
- Risk of sudden power cut-off by the BMS: when a critical operating threshold is reached, notably in the event of excessive discharge, the BMS disconnects the battery in order to protect it. There is therefore not necessarily a gradual drop in performance that would make it possible to anticipate a battery running out, such as the voltage drop on a lead-acid battery. It is therefore vital to make specific provisions in case such a disconnection occurs: uninterrupted backup system via a second battery, imminent cut-off alert at the helm station…
- Modification of cables and protections: The exceptional characteristics of lithium batteries have consequences for the installation itself. Their high charge current often necessitates reviewing the corresponding cables and, consequently, their associated protections (fuses or circuit breakers). However, the most significant development concerns the protection of the battery or battery bank due to their very high short-circuit current. The use of suitable fuses (in practice, only Class-T fuses have sufficient interrupting ratings) is imperative to ensure safe operation.
- Price: for the same capacity, lithium batteries are more expensive upfront than traditional batteries, even if the possibility of using their full capacity and their much longer service life can offset part of this gap.
Marine lithium battery and fire risks
The fire risk is often presented as central for lithium batteries. This is entirely logical given the consequences of a fire on board a vessel.
Like all lithium batteries, LiFePO4 technology batteries present risks of fire and/or gas release (toxic, flammable, corrosive) resulting from thermal runaway.
However, this risk is considered low, even very low compared to other technologies. Indeed, the thermal runaway threshold is very high (≈270°C) while the rate of temperature rise remains low in the event of failure (≈1.5°C/min) and the volume of gas released in this case is limited (80% less volume than NMC batteries, for example).
As a lead-acid battery can also release flammable gases, we consider that the fire risk is not significantly higher after installing LiFePO4 lithium batteries on board.
What do the standards regarding lithium batteries say?
The ISO 23625:2025 standard (“Small craft — Lithium-ion batteries”) specifies the requirements and recommendations for the selection and installation of lithium-ion batteries for boats.
As for the ISO 13297:2020 standard (“Small craft — Electrical installations — Alternating and direct current installations”), it specifies the more general rules for electrical installations on board recreational craft and therefore, among other things, the installation of lithium batteries.
Lithium Battery: Performance Requiring Controlled Installation
High usable capacity, reduced weight, extended lifespan, and fast charging explain the growing success of onboard lithium. However, safely benefiting from these performances requires designing or adapting the electrical installation as a whole, well beyond a simple “battery replacement”.
Shipyards, naval architects, nautical professionals or leisure boaters: Koriolan supports you in the design, sizing and integration of your electrical installation, for new build as well as refit. Our teams operate throughout France (on the Atlantic coast, in the Mediterranean and in the English Channel) and across Europe (from the Baltic to the Black Sea).
By Séverine Korovic
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