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Maritimo 2023 S-Series LEADERBOARD

Powering Adventures: the growing market for lithium batteries

by Ryan Ellison/ Dakota Lithium 17 Aug 2023 11:41 PDT
Powering Adventures - Lithium Iron Phosphate batteries © Dakota Lithium

Lithium batteries have brought about a paradigm shift in energy storage, providing numerous advantages over traditional battery technologies. Their remarkable features, including high energy density, longer cycle life, and impressive power-to-weight ratios, have made them particularly appealing for use in sailing yachts and motor vessels.

As the demand for electric vehicles continues to soar, the lithium battery industry has experienced unprecedented growth. Notably, many sailors are now upgrading their systems to harness the benefits of lithium batteries. Compared to lead-acid batteries, lithium batteries weigh only half as much, offer double the capacity, and have a significantly smaller footprint. This not only allows for increased storage capacity but also enables power-hungry applications like autopilots to operate throughout the night without relying on engines or generators.

A recent report by Li-Bridge highlights the surge in demand for lithium-ion batteries, estimating a five-fold increase by 2030. The projected annual revenue is expected to reach a staggering US$33 billion, creating over 100,000 jobs in the US.

However, amid this rapid growth, concerns have been raised regarding alternator fires, incidents of boats sinking due to lithium battery fires, damage to entire electrical systems caused by dump loads, and the misconception that lithium batteries are a simple "drop-in" replacement for lead-acid batteries.

To address these concerns and dispel any misinformation or confusion, it is important to explore the various lithium battery chemistries, safe charging practices, fire risks, installation approaches and the implication on insurance coverage.

To provide expert insight on these matters, we turn to Ryan Ellison from Ryan and Sophie Sailing (our article about them can be found here), an ABYC Certified Electrical Technician. With extensive sailing experience, including 25,000 nautical miles and three ocean crossings, Ryan is a founding member of Dakota Lithium. His involvement in the lithium industry and comprehensive testing of Dakota Lithium batteries on their own yacht, Polar Seal, makes him well-equipped to debunk myths and provide essential considerations for installing lithium batteries on boats.

Watch this before installing lithium batteries on your sailboat

Lithium Chemistry

Opening up a lithium battery pack reveals cells inside, which can vary in shape and size. These cells, whether cylindrical, prismatic, or contained in a pouch, are wired and structured to achieve the desired voltage and capacity for the desired battery design.

Each cell consists of an anode material, a cathode material, and an electrolyte or medium through which electrons flow between the anode and cathode to release stored energy.

Lithium batteries can be made with different materials for the anodes and cathodes, resulting in various lithium chemistries.

The most common ones are Lithium Cobalt Oxide (LCO), Lithium Nickel Magnesium Cobalt Oxide (NMC), and Lithium Iron Phosphate (LiFePO4).

LCO batteries are most commonly found in phones, laptops, and cameras, offering high energy density but with a limited cycle life and an inability to be charged at high current rates.

NMC batteries, prevalent in power tools, e-bikes, and power systems, provide high capacity and power but with a moderate cycle life.

And finally, LiFePO4 batteries, which are most commonly recommended for boats, due to their high cycle life and low internal resistance, albeit with a lower energy density compared to other lithium chemistries.

Fire Risk and Thermal Runway

One key benefit of lithium batteries is their ability to handle high charge and discharge rates or to power ‘hungry’ applications that demand high current draw, such as water heaters. This increased capacity comes with the risk of generating heat within the battery cells. Similar to running high currents through a wire, prolonged high-capacity usage can cause overheating and damage to the cells, potentially leading to the risk of fire.

This is the most common concern from sailors looking to upgrade their batteries.

Damaged cells cause a chain reaction, rapidly increasing the temperature within the battery. This is called thermal runway and is usually the consequence of a variety of factors including: thermal failure, as a result of extreme temperatures (either too hot or too cold), mechanical failure (such as physical punctures or faulty connections within the battery pack), or internal / external shorts (direct contact between positive and negative ends). Additionally, abusing the battery or not following the manufacturer's recommendations can also trigger the phenomenon of thermal runaway.

The fire hazard associated with lithium batteries stems from the temperatures at which they enter thermal runaway. Lithium Cobalt Oxide (LCO) batteries experience thermal runaway at approximately 150°C, while Nickel Magnesium Cobalt (NMC) batteries reach thermal runaway around 210°C. Lithium Iron Phosphate (LiFePO4) batteries have a higher thermal runaway temperature of around 270°C, making lithium phosphate the preferred choice for yachts. Comparatively, lead-acid batteries reach thermal runaway at approximately 400°C.

To establish the safety of lithium batteries, The Federal Aviation Administration (FAA), conducted a comprehensive study on thermal runaway on lithium batteries in different cell configurations. Not only did lithium iron phosphate (LiFePO4) perform the best from a safety and thermal runaway perspective, they found that if one cell in a pack went into thermal runaway, it didn’t spread to other cells in the pack.

Internal and External BMS (Battery Management System)

All lithium batteries require a battery management system (BMS) for safe operation. Without a BMS, there is a risk of thermal runaway, which as we know, can lead to fires. The BMS serves as a small computer either integrated within a battery pack or externally connected to multiple packs. Its main purpose is to protect the cells and prevent thermal runaway incidents.

Different types of BMS’ are available for various battery chemistries. Most BMS’ monitor charge and discharge current, pack or system voltage, temperature, and cell balancing to ensure consistent charge levels. If any of these parameters are exceeded, the BMS will shut down current flow to safeguard the cells and the overall battery pack.

It's important to understand the specific parameters for each battery type - the BMS on Polar Seal, for example, limits the charging voltage to a maximum of 15 volts. If the battery receives more than 15 volts due to a failed MPPT (Maximum Power Point Tracking) device, the BMS will halt the charging process. The same applies if the temperature sensor detects excessive heat in the cells.

Some batteries come with a built-in BMS, such as Dakota Lithium and Battle Born, while others, like Mastervolt and some Victron batteries, require an external BMS, which is purchased and installed separately. The key distinction between internal and external BMSs is that an external BMS can interface with multiple battery packs, enhancing cell balancing and providing the option to replace the BMS in case of a failure.

While Dakota Lithium’s batteries have an internal BMS, they are backed by an 11 year warranty without a claim for a BMS failure.

Some BMS systems offer external communication capabilities through Bluetooth or CAN bus connections, providing added safety and efficiency benefits - this connection allows them to communicate with other components in the system, such as shore chargers or alternator regulators. This communication enables those components to shut down in the event of a battery shut-off, preventing potential issues like dump loads, which we discuss later on.

The Myth of Drop-In Replacements

It is crucial to dispel the notion of a "drop-in" replacement lithium batteries. Lithium batteries are a distinct technology and require appropriate treatment. Due to their ability to charge and discharge at faster rates, thicker cables will likely be necessary to prevent overheating.

Furthermore, charge controllers such as MPPTs, wind generators, shore chargers, and alternators may require adjustments in their settings to accommodate lithium batteries' unique characteristics, such as charge voltage.

Additionally, the alternator should be properly connected through a lead-acid starter battery and a battery-to-battery charger.

In relation to BMS, it is the distinction between internal and external BMS’ that has often led to batteries with an internal BMS’ being classified as ‘drop in’. This is a dangerous fallacy designed to sell more batteries.

Regardless as to your battery design, it is imperative that your system can withstand the charging and discharging capabilities of lithium to keep you and your boat safe.

Dump Loads

Dump loads are not exclusive to lithium batteries; they also pose a risk with regular lead-acid batteries.

Dump loads are a potential concern when using high-amperage charging devices like high-output alternators or shore chargers. If access to the battery is abruptly cut off or the BMS shuts off charging, a voltage surge occurs in the system. In a 12-volt system, this surge can reach anywhere between 40 volts and 120 volts and take up to 400 milliseconds to decay. Such voltage spikes can cause significant damage to voltage-sensitive electronics, alternators, and chargers, similar to the effect of a lightning strike.

Proper installation is crucial for mitigating the risk of a dump load and attention should be given to secure cable connections that can withstand heavy vibration or rough seas.

As Dakota Lithium, we haven’t found dump loads to be commonplace if the batteries are installed correctly.

Safe Charging

When it comes to charging lithium batteries, it's essential to adhere to safe charging practices.

Each battery has a specified charge current rating, typically around 0.5 times the battery capacity (C2) or higher. As an example, a 170 amp-hour battery can typically handle a charge rate of 85 amps or more. If multiple batteries are connected in parallel, the total charge capacity increases accordingly. However, even if one or two batteries fail, the remaining capacity should still align with the charging device's capability.

On Polar Seal, we have four 170 amp-hour batteries in parallel which allows us to use 85 times 4 or 340 amps. Should one or even two of these batteries fail, we still have 170 amp charging capacity. We have no charging device on board that could exceed this charging rate.

In theory, it would be very rare to see systems that contain for example one 200 amp hour battery and 180 amp high output alternator. If you do have a system that has a charger bigger than the charge capability of your lithium batteries, incorporating redundancy measures to protect the batteries becomes necessary.

Safe Charging and Alternators

When connecting lithium batteries to alternators, it's important to consider the difference between lithium batteries' high-current acceptance and the basic nature of most alternators.

Alternators are designed to provide power without considering the specific battery's characteristics. When the alternator runs at a high output for an extended period, it generates heat that is typically cooled by the engine-driven fan. In situations where the engine operates at low power or low RPM, the fan may not supply sufficient cooling air, leading to potential alternator damage or fire hazards.

To mitigate this risk, one option is to externally regulate the alternator. This is recommended for all battery types, not just lithium.

Another approach involves using the alternator to charge a lead-acid starter battery and employing a battery-to-battery charger to charge the lithium bank. This method provides a safe solution that reduces the risk of dump loads. However, it may limit the lithium batteries' charging rate to a level lower than their full capability, potentially diminishing the advantages of lithium technology.

Onboard Polar Seal, the alternator was connected to an external regulator, allowing direct charging of the lithium bank. The plan is to replace the AGM starter battery with a Dakota Lithium starter battery due to their expertise in lithium starter batteries.

Whichever route you take with charging, it is important that measures are taken to avoid costly and damaging alternator fires.

Lithium Batteries: What makes for a safe installation onboard?


Maintaining insurance coverage is one of the biggest concerns for cruisers looking to install lithium on their boat. For this point, we reached out to Mike Wimbridge at Pantaenius, who advised that ‘it is best practice for every cruiser to speak to their insurance company BEFORE they contemplate an install’.

‘Lithium batteries are not a new technology but in a time when we want to be mitigating risk, it is prudent to start by telling your insurance company of your intention to install batteries. Ensure you have a qualified marine electrician professionally install your batteries and that you understand all the upgrades needed to your system - bigger cables, fuses and busbars, for example and your system can handle the increased power draw. At the very least have your system inspected and signed off by a marine electrician to confirm that your boat complies with these best practices.

Some insurers have clauses in their policies to this effect, however, you are running a risk by not getting lithium professionally installed, not only to you but also to the boats around you’.

While some cruisers are opting to build their own battery banks, this does cause concern to many insurers with some not opting to insure - this is usually dealt with on a case-by-case basis, particularly where people are sourcing their batteries from Alibaba and the quality of the cells are not guaranteed - and with very little comeback should there be an issue.

There are many reputable places to buy lithium phosphate cells. You just need to be extra cautious in your installation approach should you decide to go this route. Check your insurer is happy with you building your own bank, select a reputable BMS with the correct settings that are correct for your system and, most importantly, get the installation signed off’.

In conclusion

To ensure a safe installation of lithium batteries onboard, I recommend the following:

• Purchase lithium-ion phosphate batteries
• Source batteries from reputable and well-known suppliers with good technical support.
• Ensure the installation is performed correctly by a skilled lithium installer, using cables with the appropriate rating for your application and high-quality components, fuses, and bus bars.
• Manage alternator charging either through an external regulator or by utilizing the starter battery method.
• Get your installation signed off by a qualified marine electrician

Installing lithium batteries involves various considerations, including the upfront costs of batteries and component upgrades, which can be a significant investment during the initial installation phase. However, the benefits of lithium batteries having a life-cycle ten times longer than lead-acid batteries, being half the weight, with a smaller footprint - you won’t go back to lead-acid!

Just remember, careful evaluation of risks, proper installation, and selecting suitable components are crucial for a safe and efficient lithium battery system.

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