Cell protection from short circuits

A large number of systems have been developed for the protection of cells from short circuits. Titanium anodes are destroyed by short circuits and must be raised before any contact with the amalgam takes place. 

The chief problem with outdoor installation is the exposure to weather, especially in a cold climate. A building not only protects woikers fix>m exposure to the weather, it also shields equipment from sun, rain and snow (with their thermal shock), sand and dust storms, and corrosion. The protection offered by a building slows the natural process of deterioration of system components and helps to avoid foreign deposits that can allow short-circuiting of cell connections. 

In order to limit the dangers inherent to thermal runaway, these external safety devices are supplemented within the cell itself by internal protective mechanisms, such as shutdown separators (discussed in section 5.5.1), which are effective for temperature ranges from 135°C to 160°C beyond this temperature, they become ineffective, because they lose their mechanical integrity, leading to the two electrodes coming into direct contact and an internal short-circuit. This type of separator tends to be found generally in high-capacity elements. 

Current-limited intrinsically safe battery packs have build-in protection that ordinary battery packs do not have, and these current-limiting devices will provide protection from external short circuit. However, two elements that are not mitigated by intrinsically safe design are partial short circuit (where a failure internal to the battery pack causes short circuit of a subset of cells, e.g., one series or parallel string) or an internal short circuit. 

The cells can be operated with success at elevated temperatures. When operated at very high currents outside the recommended limits, the cells may produce heat and high internal gas pressures and these conditions should be avoided. The cells are, however, an excellent source for high pulse currents. Multi-cell batteries contain additional insulation as well as a fuse for protection from mishandling such as short-circuits. 

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