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Lithium-Ion Batteries for Racing Yachts
Published Wed 17 Dec 2025
Lithium batteries can store a lot more energy with lower weight are becoming more practical and affordable. What are the benefits and problems boat owners need to consider?
Batteries provide a critical source of power on racing yachts for:
- Engine starting and house power.
- Electric motors and demountable motors on smaller yachts
- New technology in navigation and communications
- Portable devices from crew
Typically, AGM batteries are the most common type of battery technology currently used in racing yachts.
However, lithium-ion batteries (LiB) are increasingly common today as the provide the power to many devices that we use in our everyday lives. Laptops, mobile phones, watches, caravans, electric vehicles and now increasingly racing yachts and all use LiB in one form or another but there is large diversity in the range of LiB that are now available.
1. Types of LiB
a. Types of Li-based battery chemistries.
There are a number of different Li-based chemistries that are used in batteries, each with their individual properties with regard to electrical performance, cost, lifespan and safety. The diagram below shows the most common chemistries and their application. The further long a given dimension indicates superior performance.
b. Form Factors of LIB
LiB’s come in three main form factors; cylindrical, prismatic and pouch. The prismatic form factor makes it ideal for incorporation into replacement for traditional AGM yacht batteries and to provide the strong mechanical strength required in marine applications.
2. The Advantages of LiB
a.For given amount of stored energy, up to three times lower in weight.
b.Can be charged and discharged much faster than their AGM equivalents.
c.Can tolerate higher levels of discharge compared to AGM batteries.
d.Can accommodate a higher number of charging cycles.
e.Have a very low self-discharge rate.
3. The Disadvantages of LiB
a.Higher initial cost but given the more tolerant charging characteristics and higher number of possible charging cycles, lifetime cost may not be that different to AGM’s.
b.Can overheat (thermal runaway) and need to be controlled by an effective battery management system (BMS) to oversee all aspects of the battery operation.
c.Can be problematic to extinguish a fire from an overheated battery.
LIB For Racing Yachts
The overall combination of performance, durability, safety and cost make the lithium iron phosphate (LFP) chemistry the clear preference for marine applications (based on an assessment of all of the characteristics shown in the diagram above). Prismatic cells are usually arrayed in a form that makes them an easy replacement for the traditional lead acid AGM batteries.
This report focusses on the use of LFP batteries for house battery electrical supply for racing yachts. It should be acknowledged that there have been a number of battery fires linked to LiB powered devices, but these have been associated with charging of electric scooters, powered waveboards and other LiB powered devices. These devices typically involve less safe lithium chemistries, are not as well regulated (often not meeting the recognised standards) and should generally not be left charging unattended on racing yachts.
1. Key Requirements for LiB in Yachts
a.Compliance to Standards
It is key that all batteries used in racing yachts comply with the AS IEC 62619 standard. This is an international standard that has been adopted in Australia and ensures that the battery has undergone a thorough set of tests to assess the electrical and mechanical performance of the entire battery system. The standard covers the design and assembly on the battery units, tests to assess the normal electrical operation of the battery system, the battery management system and various scenarios of abuse to the battery.
There are some cheap, non-standard certified, batteries available but only those meeting this standard should be approved for use in racing yachts.
b.Installation of LiB
LiB should be installed according to the general wiring standard AS/NZS 3000 and more specifically AS/NZS 3004.2 which covers electrical installations for marinas and recreational boats. The batteries should be housed in a dry area that is not subject to temperature extremes. AS/NZS 3001.2 is a very new standard (2022) that covers battery installations in recreational vehicles. It is applicable where batteries are used to provide house power to things like caravans but reasonably includes yachts and does specifically cover LiB. In addition to covering the mounting and electrical connections (which must be 300mm, distant from any gas, diesel, water lines unless the battery is housed in its own box). This standard also requires that batteries must be located externally i.e. behind a wall, compartment or barrier that prevents any vented gases entering the habitable area of the recreational vehicle. The great majority of cases with racing yachts involve retrofitting old AGM batteries with LiB and while maybe this requirement may not apply, that it does exist for new installations and demonstrates a concern about the possibility of gases from the battery entering the living area (see below).
The CSIRO team we consulted recommended that only a single connection be made to the battery and other electrical connections be made through a bus bar arrangement. They also recommended locating the battery so that it could be more easily thrown overboard in an emergency (though still needing to be well secured!).
The take home message for installing LiB in a racing yacht is that this is not a job for the amateur electrician!
It should be mentioned that many small keel boats (J70’s etc.) use electric motors for their required propulsion. The batteries are charged on land and then stored in waterproof pouches in the cabin and are moved to the stern of the boat to power the small outboard as needed. Should there be a fire problem with these batteries, they are easily disconnected and dropped overboard as needed so are not considered a serious risk.
c.Operation of LiB
- Batteries should only be charged by the charger recommended/provided by the battery supplier and alternative chargers should not be used.
- The battery operation should be overseen by a battery management system (BMS). Early versions of LiB had the BMS external to the battery but more recently they have been incorporated into the battery package itself. The CSIRO team were clearly in favour integrating the BMS into the battery as it enables more effective monitoring of the battery operating parameters. The BMS:
- Monitors: Tracks the battery's voltage, temperature, state of charge (SOC), and state of health (SOH)
- Protects: Prevents damage from overcharging, over-discharging, short circuits, and thermal runaway
- Balances: Ensures each cell is fully charged before the entire battery is charged
- Optimizes: Continually improves the battery's performance
- Reports: Communicates the battery's status to other devices
It is imperative that a LiB be operated and controlled by the appropriate BMS recommended for the particular battery or incorporated into the battery itself.
d.Maintenance of LiB
Manufacturers generally recommend that the lifetime of LIB will be optimised by keeping them in the 20-80% charge state and avoiding charging or discharging extremes. Regular battery inspection to ensure that area is dry and there are no obvious signs of battery deformation should be undertaken.
e.LiB Fires
The biggest concern regarding LiB is the possibility of thermal runaway (a given cell overheating leading to heating of adjacent cells) that can lead to a fire in the worst case. Not only can the battery catch on fire, but it can emit toxic gases in the meltdown process and if inhaled can represents a serious health risk.
In land-based scenarios, often the advice is to leave the battery alone and call the fire brigade but that is not an option available to yachts at sea!
In large ship installations, the batteries are usually housed in a sealed compartment which may also have some form of extinguishing system (usually water based to take the heat out of the battery) and venting but that is not the case in a typical racing yacht. There are extinguishers available that claim to be effective against LiB fires (e.g. the F-500) but they tend to be large (4L), heavy (over 6kg) and expensive. LiB fire blankets are also available.
The CSIRO team recommended locating any LiB such that they could be readily disconnected and dumped overboard in a fire situation.
Clearly, the best strategy is to avoid a fire in the first place through proper product selection, professional installation and ongoing battery maintenance/inspection. Gas monitoring, to detect any battery off-gassing, is also an option to consider.
