How to select a battery system for your ship

14 Apr

Written By Syb ten Cate Hoedemaker

With the increasing number of maritime battery systems available on the market, it can be difficult to keep an overview of the different types of systems and what is most interesting for your type of ship. The Maritime Battery Forum has gathered information from many of the different maritime battery manufacturers and created a quick overview to help you understand the differences between the currently available systems and how to find out what it is that you need.

You can find the document in PDF here: Maritime Battery Forum - Which battery for your ship?

Types of Lithium-ion batteries

Currently, Lithium-ion batteries are best suited for powering ships. However, there are many different types of Lithium-ion batteries, each of them optimized for a different type of application. In maritime battery systems we mainly use NMC, LFP and LTO.

Battery cells

The smallest building block of a battery system is the battery cell. Cells come in different shapes and sizes, resulting in a varying performance per type of cell.

Battery system design

Also battery systems come in different shapes and sizes, varying in flexibility in design and ease of integration. Some systems can be more easily fitted on smaller ships, others are more optimized for larger ships.

The exact type of battery cell being used has its impact on certain aspects of the battery system, but is mainly important for the battery manufacturer’s design choices. When selecting a battery system for a ship, what matters most is how the battery will be used regarding the required energy, (dis)charge power and the number of times the batteries will be charged and discharged, also known as the number of cycles. This will have impact on the ideal battery system design for your specific vessel when it comes to weight, volume, costs, performance, and lifetime.

Battery applications

Batteries can be used for all different kinds of applications on board of ships. Not all ships can be fully powered by batteries, but every ship can benefit from installing a battery, creating a hybrid or plug-in hybrid system. This can be for zero-emission sailing, increasing the energy efficiency, or enhancing the performance of the ship.

Operational profile

To make the right decision on which battery to select, you should start with defining the operational profile of the batteries. Some ships will have different operational profiles, depending on the conditions or operational activities. The more elaborate you define the operational profile, the better you can optimize the battery system design. The most important information for the battery manufacturer to receive is listed here on the right. It is not recommended to define a total installed capacity to a battery manufacturer, as this is very much depending on the type of battery in combination with the operational requirements.

Primary requirements to select a battery

• Minimum required usable energy in kWh

• Maximum discharge power in kW

• Maximum charge power in kW

• RMS value of (dis)charge power in kW (RMS = Root mean squared)

• Number of cycles per year

• Time per (dis)charge period

Battery sizing

The total installed capacity that is required depends on the type of battery and the operational profile. Typically the top and bottom SOC are not used to increase the expected lifetime of the batteries. Depending on the usage of the batteries, the capacity will decrease over time, this is called aging. This results in only a certain part of the capacity that can be considered as usable. The total required installed capacity for your ship can be calculated by the battery manufacturer as they know their batteries best. Different batteries require different sizing strategies.

Lifetime

Batteries decrease in capacity over time, called aging, which results in a certain lifetime for batteries. There are two types of aging: calendar aging and cycle aging.

Calendar aging is the decrease in capacity over time, without the battery being used, and is mainly depending on the temperature and SOC of the batteries. Batteries prefer temperatures around 20°C and a SOC around 50%.

Cycle aging is the capacity loss with every cycle that is made, and is mainly depending on the DOD and the C-rates. In general, a smaller DOD results in less capacity loss, although the effect varies per type of battery. In general, the higher the C-rates, the higher the loss of capacity.

Performance

The performance of a battery system depends on multiple factors. In general, maritime battery systems can be categorized as high energy, medium energy and high power batteries, based on the energy density and the maximum continuous discharge C-rates they can endure.

All batteries can be used for all types of ships, but some are more suitable than others depending on factors such as weight, volume and costs. These all need to be assessed to create a complete picture of the battery system design and to be able to compare different types of battery systems with each other.

Other requirements

There are many other things that can be considered when selecting the right battery system for your ship. Here is a list of the main aspects that should not be forgotten.

• Voltage

  what is the required voltage range for the batteries

• System costs

  system costs vary between 400 and 800 Euro/kWh

• Cycle costs

  also calculate the costs per cycle, depending on lifetime

• Safety

  cell or module level thermal runaway propagation insulation

• Firefighting

  water mist, foam, or inert-gas, depending on the IP-rating

• Ventilation

  closed or open ventilation system for emergencies

• Gas detection

  is gas detection integrated in the battery system or not

• Cooling

  liquid or air cooled, depending on the environment and usage of the batteries

Terms and abbreviations

SOC = State of ChargeSOH = State of HealthDOD = Depth of DischargeEOL = End of LifeC-rate = (dis)charge rate (kW/kWh)kW = kilowatt (power)kWh = kilowatt-hour (energy)

For more questions about maritime batteries, reach out to the Maritime Battery Forum via director@maritimebatteryforum.com

Syb ten Cate Hoedemaker

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