Description: Built in Four Wire Battery Measurement: The tester applies four wire to test battery voltage and internal resistance of 18650 lithium battery and AA/AAA alkaline battery with high precision. Wide Viewing Angle LCD: Extremely clear display for voltage+internal resistance+SOC with green backlight. High Accuracy with Cabin Structure: This is featured as high integration and small volume for convenient carrying,suitable well for mobile battery detection with high precision and simple operations by a pure button on the device without external accessory that is easy to operate. Backlight Adjustable: Short pressing the button to on/off on the backlight. Type C Charging Port: 3.7V/1000mAh backup lithium battery. Charged by 5V charger(such as mobile phone charger).If there is no button or test action within 30 seconds, the LCD screen and backlight will automatically turn off and enter the hibernation state. Specification: Charging time: 1.5 hours Backup battery working time: backlight off: 45 hours; backlight on: 25 hours Backup battery cycle charging times: ≥ 1000 times Material: ABS Plastic Size Chart: 156x63x36/22mm/6.14x2.48x1.42/0.87inch Package Includes: 1 Piece Battery Internal Resistance Voltage Tester 1 Piece USB Cable