Thermal runaway is a catastrophic overheating of the battery, causing a fire that generates toxic gases and risk of explosion. The fire can propagate between batteries and adjacent materials/structures. In a marine environment, this obviously causes great danger to the crew, the ship and any passengers on board.
Causes
There are a number of different ways thermal runaway can occur, as shown in the diagram below.
Image courtesy of SHIFT Clean Energy
Prevention
Maintaining low cell temperature at high power cycling or in a fault scenario is the key to lithium-ion safety. Keeping the internal temperature of each cell below the thermal runaway threshold ensures prevention.
For specific causes, the prevention measures below will remove the risk of thermal runaway.
| Cause
|
Prevention
|
| Negligent Charging / Discharging | Include voltage upper and lower limits using BMS software and hardware sensing of each cell with direct trip line to DC breaker |
| High external temperatures | Encase cell in cooling liquid to prevent heat from reaching the cell.
Ensure cooling water is flowing at all times and prevent external fire from reaching batteries. |
| External Short Circuit / High Current | Encase cell in cooling liquid to prevent heat from reaching the cell. |
| Mechanical Damage | Crush proof cell casing passing UN38.3 transportation tests.
SPBES PlanB uses 19mm of aluminum armor protecting cell edges. |
| Dendrite Formation | Encase cell in cooling liquid to prevent heat from reaching the cell. If an internal short occurs from dendrite or manufacturing defect – the liquid cooling is able to remove more heat than a runaway cell is able to produce. Required coolant flow between 0.5GPM and 2GPM for RMS C rates between <0.1 and 3C. |
The Patented SPBES Thermal Management System is designed to prevent thermal runaway. Through thorough cooling of the cell, we facilitate the ability to use all of the available energy within the cell to its full potential- safely. By taking the heat away from the cell as it is created, we keep the cell temperature at ideal performance range (around 25 °C) and prevent the internal cell temperature from accelerating to the point where thermal runaway occurs.
– Information from SHIFT Clean Energy –