Meaning
Internal electrical fault where one cell in a parallel group fails and triggers a discharge from adjacent cells can cause a rapid, localized thermal event. In a parallel cell short circuit, the healthy cells in the group discharge their energy directly into the defective cell through the shared busbar. This unmanaged current flow can lead to high temperatures or thermal runaway if the energy is not dissipated.
Pack designers must incorporate safety features to isolate individual cells within a parallel block.
Isolation Feature
Fuses or wire bonds can be used to disconnect a failing cell from the parallel group automatically. When a parallel cell short circuit occurs, the high current flowing through the fuse causes it to melt and open the circuit. This action isolates the defective cell and protects the rest of the group from draining or overheating.
Sourcing the correct gauge of fuse wire is essential to ensure reliable activation under fault conditions.
Thermal Simulation
Thermal models help engineers predict the temperature rise of a multi-cell pack during an internal fault. These simulations show how heat spreads from the shorted cell to its neighbors and allow designers to optimize cell spacing. This planning prevents a single-cell failure from propagating into a full-pack thermal event.
Sourcing Consideration
Purchasing departments must evaluate the quality of the separator materials inside the cells they source. Separators with high thermal shutdown temperatures minimize the risk of an internal short circuit occurring in the first place.
