What’s the PTC of the li-polymer battery, and what’s the function? How does it work and protect the li-polymer battery?

The PTC (Positive Temperature Coefficient) thermistor is a critical safety component often found in Li-Polymer (Lithium Polymer) battery packs. It functions as a protective device that responds to temperature changes.

Function of the PTC in Li-Polymer Batteries:

  1. Overcurrent and Short Circuit Protection: The primary function of a PTC in Li-Polymer batteries is to protect against overcurrent and short circuit conditions. When a large current flows through the li-polymer battery, either due to a malfunction in the device it powers or a short circuit, the temperature of the li-polymer battery increases.
  2. Temperature Sensitivity: Unlike regular resistors, a PTC thermistor’s resistance increases as the temperature rises. This characteristic is leveraged to protect the li-polymer battery in abnormal conditions.

How the PTC Works:

  1. Regular Operation: Under normal operating conditions, the PTC has a low resistance, generally allowing the li-polymer battery to function without significant power loss.
  2. Response to Excessive Current: In the event of overcurrent or a short circuit, the current flowing through the li-polymer battery increases significantly. This leads to a rise in the temperature of the PTC thermistor.
  3. Resistance Increase: The PTC’s resistance increases rapidly as the temperature rises. This increase in resistance limits the current flowing through the li-polymer battery, reducing the risk of overheating, which can lead to li-polymer battery damage or even safety hazards like fires or explosions.
  4. Automatic Reset: Once the overcurrent condition ceases and the temperature drops, the PTC cools down, and its resistance decreases back to a low level, allowing regular li-polymer battery operation to resume. This automatic reset feature is a significant advantage of PTC thermistors.
  5. Complementary Protection: The PTC thermistor is usually used in conjunction with other protective components, such as a Protection Circuit Module (PCM) or a Li-Polymer Battery Management System (BMS), which provides overcharge, over-discharge, and short-circuit protection.

Protective Role of PTC:

Including a PTC in a Li-Polymer battery pack enhances overall safety by providing a responsive and self-resetting protective measure against excessive current and overheating. It’s an essential component for preventing thermal runaway – a dangerous condition where increasing temperature leads to further increases in temperature, potentially leading to li-polymer battery failure or combustion.

In summary, the PTC thermistor in a Li-Polymer battery acts as a temperature-dependent current limiter, ensuring safer li-polymer battery operation, especially under fault conditions like overcurrent and short circuits.

 

2S Li Polymer Battery Storage

2S Li Polymer Battery Storage

This instruction manual provides guidelines for safely storing 2S li polymer (LiPo) batteries manufactured by LIPOL BATTERY Co., Ltd. Please follow...

18650 26650 & 21700 Battery

18650 26650 & 21700 Battery

What's the difference between 18650, 26650 & 21700 batteries?Understanding the Differences Between 18650, 26650, and 21700 Lithium Batteries:...