NTC thermistor used in protecting LiPo battery pack

These small epoxy encapsulated bead Negative Temperature Coefficient (NTC) Thermistors are commonly found siliconed to an 18650 cell in laptop battery packs. This table shows some measurements of the (no-load) resistance compared to the reading from an adjacent DS18B20 sensor.

From the data it can be surmised that:

  • the thermistor has a negative temperature coefficient (resistance increases with decreasing temperature
  • the design resistance is probably 10kΩ at 25℃
Temperature/℃Resistance/kΩ
5.2521.81
18.0612.61
18.4412.43
18.4412.47
19.1212.57
20.2511.14
20.8111.03
Note the specified temperature accuracy for the DS18B20 is ±0.5℃ from -10℃ to +85℃
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