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ELECTRIC VEHICLE BATTERY PERFORMANCE pack, the electronic control module, the motor, the battery charging port, and other high-voltage components. Running parallel to these high-voltage cables is an additional pilot circuit that acts as a simple continuity loop. The pilot circuit is integral to the high-voltage charging cable such that it is not possible to disconnect. In the event that a break occurs in the charge cable it happens by doing the same to the pilot cable. If an accident occurs that results in the high-voltage and causes the pilot cable to disconnect, the pilot circuit records the loss of electrical continuity. It will automatically disconnect the high-voltage cabling from the battery pack. The location of this pilot circuit disconnect system is also vehicle-specific but is typically found in proximity to the vehicle battery pack. Many vehicle manufacturers employ a combination of the disconnect systems for both redundancy and safety purposes. Whether a ground monitor, inertia switch, or pilot circuit is used, it is important to know that these devices isolate the rest of the vehicle only from the traction battery pack voltage. However, lethal levels of electric current may still be present in the battery pack. It is of utmost importance that an EV battery pack be treated with the same caution and respect as a full gasoline fuel tank in an internal combustion vehicle. All current OEM EVs also have special manual disconnects that decouple the battery pack from the remainder of the vehicle wiring and systems. The locations of these disconnects are very vehicle-specific and are intended to be used mostly by vehicle service personnel during periodic maintenance procedures. Newer electric bus models now have a manual disconnect located on the driver’s control panel. This allows for additional safety in the event that the inertia switch, ground monitor, or pilot circuit fail to disconnect the battery pack from the vehicle wiring systems.
SAFETY IN BATTERY DESIGN Battery electrolyte decomposition can be hazardous to the EV operator. Overheating of the traction battery pack accelerates the electrochemical reaction that causes electrolyte decomposition. During the first charging cycle, the process of initial formation of the interfacial films leads to the electrolyte reduction. This reduction may continue in to the subsequent charging cycles with certain combinations of the negative electrode and the electrolyte materials. In addition, electrolyte decomposition leads to phase changes, which can also pose hazards to the EV operator. The organic liquids identified
