Ask Andrew: Advantages and Disadvantages of Lithium Batteries

a deep cycle lithium marine battery

Jan 7, 2025

I’m not a frequent traveler so I’m still getting used to airports and the ins-and-out of airplane travel. I finally took a trip in November and during the safety spiel, I was surprised to hear a warning about cell phones. Essentially it said: if your cell-phone drops, don’t try to retrieve it. Instead, call a member of the flight crew for assistance, because it poses a fire hazard.

Naturally, this got me thinking. I did some light digging and found that the issue isn’t limited to cellphones. We carry around a lot of lithium battery powered devices, daily: phones, AirPods, laptops, tools, vapes. It turns out that compromised batteries can ‘undergo thermal runaway’ which involves ‘violent bursting’ and ‘intense, self-sustaining fire’. According to the FAA, this is a weekly occurrence on aircraft operating in the US.

Other recent stories, articles and news-worthy events also came to mind: Tesla’s electric cars catching spontaneously on fire. Certain underground private garages banning electric vehicles due to the fire hazards they pose, and townships implementing stricter rules and sorting techniques after garbage truck and dumpster fires have become more prevalent. Finally, 2025 has been a rough start for a Chinese tool manufacturer who does business in the US and Canada: A class action lawsuit has been filed due to the fire hazard that their lithium batteries present.

Lithium batteries were once (not so long ago) touted as the next best evolution of battery design, displacing lead-acid and AGM batteries as the preferred type. These warnings show that there are lots of questions and issues facing the full adoption of the lithium-ion technology on boats.

There is zero doubt that Lithium batteries have significant advantages over lead-acid and AGM: They are light – extremely light. They have larger capacity (they can power more stuff for longer), they are maintenance-free, they have a higher number of re-charge cycles (they can be discharged and re-charged more times in the battery’s lifespan than their lead-acid and AGM cousins). Finally, lithium batteries don’t lose charge over time so you can be assured that if you put your boat away at haul-out with 12V in the lithium batteries, they will still read 12V in the spring when they are reconnected.

The most important thing to recognize is that where lead-acid and AGM batteries are cousins to Lithium batteries (in that they provide current to power electronic devices) – they are more like distant 3rd cousins. I would use an even stronger analogy and say that they are more like a glass of water and a glass of alcohol: they look the same from a distance. They can be confused close-up – but one will quench and one will burn.

Let’s dive into some specifics:

1. Lithium battery construction is much different than conventional batteries. The total voltage is comprised of multiple cells. Controllers inside the battery monitor and maintain the usage of each cell.

• The boat’s total system is limited by the weakest battery, and the weakest battery is limited by its weakest cell.

• A lithium battery requires a battery management system (BMS) to monitor and maintain the system. They also require lithium-specific battery chargers.

• On a boat, batteries can be mixed and matched to some degree. Ie: Lithium batteries can be used to power the house system, and AGM batteries can be used as a starter battery to start the engine. That said, separate chargers would be needed to power each battery bank.

• Conventional chargers work differently than lithium batteries: Conventional chargers look for a reading from the battery before beginning to charge. A lithium charger is based on time of charge, not on the voltage reading from the battery.

In years of early adoption, it was common to see lithium batteries overcharged and catching fire. As the technology has been adopted, charger technology has been improved and this is a much more rare occurrence today.

• Lithium batteries can be tailored to voltage requirements more easily that conventional batteries. Ie. A 36 volt or 48-volt lithium battery can be bought off the shelf. A conventional battery would need to have multiple 12V batteries connected in series to achieve a 36- or 48-volt solution.

• Lithium battery dimensions are different standards than conventional. Many of us have become accustomed to 24, 27 and 31 series batteries. Boats and storage spaces have been designed around these dimensions. Lithium batteries disrupt these spaces when they don’t fit correctly.

• Lithium batteries are being used to power trolling motors, house systems, and complex voltage-sensitive equipment (like multi-function displays and autopilots)

• BMS systems, Engine alternators and the high current output needed for starting systems don’t mix well. Lithium batteries are being used in small power sports applications, but I don’t recommend that they be used as starting batteries in marine or auto applications. When lithium batteries are used in EV applications, the motor that is being powered doesn’t require the burst of output that an internal combustion engine requires.

If you’re using lithium batteries, or considering an upgrade, think of the following:

1. Will the items that the battery is powering damage the battery through their use? Ie using a lithium battery is a starting application
2. Will you have a mix of batteries on-board? Are the battery types completely independent? How are they being charged?
3. How are you using a battery management system? What are the safeguards in place to prevent overcharging or overheating?
4. Consider your marina and storage contracts – do they allow lithium batteries on board?
5. Consult with your insurance provider to ensure that they don’t have any specific requirements
6. Consult with a qualified marine tech to ensure that your boats systems are safe and seaworthy.

Andrew McDonald is the owner of Lakeside Marine Services – a boat repair/maintenance firm based in Toronto. Andrew has worked in the marine industry for 12 years and is a graduate of the Georgian College ‘Mechanical Techniques – Marine Engine Mechanic’ program. Questions or comments for Andrew? Email him directly via:   info@lakesidemarineservices.ca