Thermal Cutoffs are non-resettable thermal protectors that provide overheat protection. Mounted in close contact with the battery, thermal cutoffs interrupt the electrical current when operating temperatures exceed the rated temperature of the cutoff. The time interval experienced between the temperature being reached and TCO action is directly related to the mounting method and location. Testing must be performed to determine the proper location and TCO rating.

Bi-metallic, creep action thermal protectors exhibit slow switching action with a narrow temperature differential between opening and closing. Selecting the correct thermostat depends on a complete understanding of the rate of temperature rise, location of the device, and charge and discharge rates of the battery, among other factors. Testing of the selected device in the application is essential.

Thermistors are a semiconductor device made of materials whose resistance varies as a function of temperature and can be used to compensate for temperature variation.

Negative temperature coefficient thermistors provide a change in electrical resistance with a change in temperature. They are an economical and accurate device used for charge control where the resistance change signals a charger to reduce or terminate charge current.