Standardizing the mechanical interfaces of swappable battery containers
On Friday December 9, the working group for the Battery Container Standardization JIP met online for a discussion on the mechanical interfaces between swappable battery container and ship. It was a good first step towards standardization of containerized battery systems by the members of the Maritime Battery Forum, but also new challenges came to light during the discussions.
About the Battery Container Standardization JIP
The concept of a swappable, containerized battery systems is being explored by many in the maritime battery industry. Battery containers can offer great operational flexibility and open up a large potential for new business models providing energy to ships and ports. The Battery Container Standardization JIP is a collaboration between members of the Maritime Battery Forum to identify the different requirements for swappable battery containers on board different types of maritime applications, and to create an overview of the different interfaces between container and ship, and their available standards. Standardized solutions for swappable battery containers will benefit everyone in the industry and increase the speed of adoption of this promising technology, but requires a significant effort in collaboration.
Mechanical interfaces
The work performed by the Current Direct project to identify the different interfaces and available standards is used as a basis for the discussion. The first group of interfaces that was discussed are the mechanical interfaces. The following topics were identified amongst the mechanical interfaces:
- General container dimensions (sizes and weight)
- Container locking
- Container lifting
- Container orientation
- Exhaust for thermal runaway
- HVAC
- Pressure relief / Purging
- Maintenance access
The general dimensions of shipping containers have a high level of standardization already, this is what makes the container interesting as vessel for swappable batteries in the maritime industry. Therefore, for the sizes and weight for swappable battery containers, the ISO 668-2020 standards are recommended as well. However, it should be noted that due to structural requirements for battery containers, it is not as simple as installing batteries in a standard 10, 20, 30 or 40 foot shipping container.
When discussing the locking of containers, the standard Twist lock seems applicable. However, there will be applications with requirements for a higher level of automatization, or requirements for a more secure fixation of the battery container on the ship’s deck. This resulted in a discussion on the definition of a ‘swappable’ battery container. So, when is a battery container considered to be swappable. Will this be depending on the interval at which the battery container is replaced by another one? A swappable battery container will also require a certain level of autonomy. The BMS and other monitoring systems should be able to continue working even when the battery container is not connect to a ship, or shore charging installation. The system might also be capable of controlling the temperature of the batteries up to a certain level, or in case of an emergency the safety systems inside should be functional. The definition on what is swappable, and what level of autonomy is required, will need a dedicated discussion on definitions in general.
When discussion the orientation of battery containers, a variation of different situations were considered. Due to the difference in available space on board different ship types, and the locations that swappable battery containers might be placed on board, it will be difficult to come up with a single standard for container orientation. This resulted in a consensus that the focus for this topic should be on standardizing the markings on containers, as well as on ships and charging stations. These markings should indicate how a particular container should be oriented, or where the specific points of interest are, such as power connections and exhausts.
Most swappable battery containers are likely to have an exhaust in case of a thermal runaway. The location of this exhaust, and the required EX-zone around this exhaust can de varying for different applications. What is important with respect to this, is that the possible locations of exhausts is taken into account in the design of the ship. So standardization of the mechanical interfaces of swappable containerized battery systems is not all up to the manufacturer of the containers only. Ship designers will play an important role in making their vessel ready for swappable battery containers and flexible in adapting different battery containers of different designs.
Next steps towards standardization
As the first discussion on mechanical interfaces raised a couple of challenges in the definitions and considerations for swappable battery containers, these topics must first be aligned with all the involved members. After that the discussion can continue with the remaining interfaces. Are you interested in becoming a part oof these discussions? Send a message to director@maritimebatteryforum.com, and join us for our next meeting in January!