Electrical cars and consumer electronics use since several years back Li-ion batteries as electrical energy storage. This means that the Li-ion battery technology is mature enough for these applications. However, in maritime applications there are some issues to be solved, especially related to safety. The battery will be in a confined space and in many cases be much larger.

In addition to having high energy density, Li-ion batteries contain combustible material and most of the chemistries do also release oxygen[1] [2] [3]. Flammable gases such as hydrogen, carbon monoxide, methane, ethane etc. are also released up on heating[4]. Heating of the battery can be caused by internal flaws, e.g. particles from the cell production[5] and poor battery management design as well as external incidents such as fire.

In order to ensure a safe electrical/hybrid electrical power vessel, all data from electrical and safety tests (on cell and battery level) should be considered as a database of information. This information is vital to ensure a proper design of the battery and the battery room for the vessel in question. Included in the battery room design are the physical dimensions of the room and systems for mitigating the consequences of a battery vent, battery fire and possible gas explosion.

There are many factors that affect the safety of lithium-ion cells, such as chemistry, size, geometry and cell environments. Aging and cycling could also affect the safety properties. We have studied the thermal response of batteries during controlled heating (calorimetric techniques). Amongst the techniques used in our study is controlled heating by the use of an Accelerating Rate Calorimeter (ARC). In this case the size, geometry and cell environment have been kept constant, while different battery chemistries are varied.

The results obtained from the ARC tests on new 18650 cells show that the highest heat rate does not necessarily correspond to the most severe physical result. The results from aged and cycled cells will also be discussed.