Whilst the electric motor is the heart of the drive system, the marine battery is your ‘fuel tank’. We can offer the right marine battery to match your performance and range expectations.
Generally speaking, there are 2 marine battery options for electric boats:
Conventional lead-acid batteries are still a sensible choice in most displacement style electric boats. Whilst they are heavy & bulky, many displacement craft have plenty of space under floorboards and under seats to store batteries. We prefer lead-acid batteries of the AGM (Absorbed Glass Matt) type. They are maintenance free, do not vent when charging and can be installed lying on their side, giving you more flexibility with the installation lay-out. Also keep in mind that many displacement boats, such as sailboats need ballast below the waterline. Often existing ballast can be removed and replaced by batteries, so they serve an extra purpose, instead of being just ‘dead’ weight.
The main benefit of lead-acid battery is their price which is relatively cheap. The drawbacks are that they are bigger, heavier and can’t be charged or discharged as deeply and quickly as Lithium batteries.
For displacement style boats that require a running time of a few hours, traveling at 4 to 7 knots and when budget is limited we usually recommend lead-acid batteries
There are several chemistries within the lithium family, for boats the most common types are Lithium-Ion Phospate and Lithium-manganese. Lithium batteries have a higher energy-density so are much smaller and lighter than lead-acid batteries. However they also are considerably more expensive. Lithium batteries can be re-charged quicker and can be discharged deeper and quicker than lead-acid batteries. They can also be left sitting in a discharged state for longer periods of time without any ill effects.
Essentially Lithium batteries win on every aspect from lead-acids. However, good marine-grade Lithium batteries with integrated battery management system and safety features are priced easily three times higher than a lead-acid battery bank of similar capacity so for some boats (or owners) they are not financially viable.
There are many ‘cheap’ lithium cells available on the market. For boating applications it’s best to use professionally designed, marine grade lithium packs with an integrated BMS (Battery Management System). Simply wiring up cells bought off the internet is ill-advised and potentially dangerous. Without a proper understanding of how lithium cells work and why they need to be electronically balanced, will result in a short battery lifespan or worse, overheating or fire of components on-board.
Both lead-acid and lithium batteries will need to be replaced after a maximum of roughly 8 to 10 years, regardless of the number of charge & discharge cycles. Typically lead-acid batteries can perform up to 500 cycles at an average depth-of-discharge. A lithium battery can perform 1,500 cycles or more (3 times as many). For recreational boaters, that use their boat on average 20 times per year (or 200 times in 10 years) this is not a real benefit. For commercial operators however the use of Lithium batteries can work out considerably cheaper in the long run as they might be going through 5 sets of lead-acid batteries in 10 years where otherwise 1 set of lithium batteries would offer the same longevity.
Below you will find 2 examples of batteries that are suitable for use in boats. They are foolproof products that can be used by everyone without specific knowledge of electronics. These batteries meet specific design criteria for use in a marine environment, such as water-resistance, shock resistance and built-in safety features to prevent damage from overcharging, overheating and immersion in water.
There are too many marine battery sizes, capacities, shapes and details to list on this website. Therefore each electric boat project will require tailor-made advice in terms of what battery bank best matches the desired range, performance and budget.
Feel free to contact us to discuss your specific marine battery needs and requirements. We can provide advice on whether lead-acid or lithium batteries would be the best match and quote you on a battery bank that suits your electric drive system of choice and matches your speed and range expectations.
As an example, please see below for more info on two popular types of electric boat batteries supplied by Eco Boats Australia: