Battery internal resistance tester

The utility model relates to the technical field of battery testing, and discloses a battery internal resistance tester, which aims to solve the technical problem of low testing precision of the existing product, and comprises an MCU (Microprogrammed Control Unit) used for generating a digital sine wave signal with a predetermined frequency, and a DAC (Digital-to-Analog Converter) unit used for converting the digital sine wave signal into an analog sine wave signal, the DAC unit is connected with a constant current source unit, the constant current source unit is provided with a power amplifier used for high-precision current output, the constant current source unit outputs a predetermined-frequency alternating current power supply to a to-be-tested battery, the constant current source unit is provided with an ADC unit used for collecting alternating voltage at two ends of the to-be-tested battery, and the ADC unit converts analog voltage signals into digital voltage signals and feeds back the digital voltage