DCIR Testing

Direct Current Internal resistance(DCIR) is one of the important indexes to evaluate battery performance.The test of internal resistance includes AC internal resistance and DC internal resistance.For single-body cells, ac internal resistance is generally used to evaluate, which is often called ohmic internal resistance.However, for large battery pack applications, such as electric vehicle power system, due to the limitations of test equipment and other aspects, it is impossible or inconvenient to directly test the AC internal resistance. Generally, dc internal resistance is used to evaluate the battery pack characteristics.In practical applications, dc internal resistance is also used to evaluate battery health, make life prediction, and estimate system SOC, output/input capacity, etc.In production, it can be used to detect faulty batteries such as micro - short circuit.

The test principle of DC internal resistance is to apply a large current (charge or discharge) to the battery or battery pack for a short time. Under the condition that the battery has not reached complete polarization, the dc internal resistance of the battery is calculated according to the voltage change of the battery before and after applying the current and the applied current.Four parameters must be selected to test dc resistance: current (or adopted multiplier), pulse time, SOC, and ambient temperature.These parameters have great influence on dc internal resistance.

The formula for DCIR is: R= UT-U0 / I

R: dc resistance, Ω

Ut: Voltage at time t of charging or discharging, V

U0: The battery voltage, V, before charging or discharging

I: Current, positive charge, negative discharge, A

Neware battery testers are able to test battery DCIR, all data will be displayed on neware self-developed software. Should you have any intereste, please do feel free to contact me by email:[email protected] or Tel:+86 18126414787.