Features FOR 18650 BATTERY --- This tester is specifically designed to measure the capacity of 18650 batteries. 1.77 inch display screen can simultaneously display information such as internal resistance, capacity, voltage, current, battery level. MULTI MODES --- The detector supports single channel capacity and internal resistance measurement; Supports separate charging and discharging, with a maximum of 9 charging and discharging cycles in automatic mode. HIGH ACCURACY --- Using DC 2 wire method to test the internal resistance of the battery, the numerical accuracy is high when the battery is fully charged. DIY METHOD --- Method 1: Install a 21700 battery holder; Method 2: Conduct testing by connecting an extension cable or crocodile clip to an external battery. DATA RESET --- When shutting down or switching modes, the capacity, energy, and time data will automatically reset. Specification: Item Type: Battery Internal Resistance Tester Material: PCB Battery: 2 x 18650 lithium batteries (not included) (power supply x 1, testing x 1) Model: XH M239 Display Accuracy: 0.1 Measurement Accuracy: 1mAH Standby Current: 5mA Discharge Current: About 500mA Load Power: 10W 8Ω Applicable Batteries: Suitable for batteries meeting stop discharge voltage of 2.5-3.5V, 2.8V start to 4.2V fully charged Package List:1 x Battery Internal Resistance Tester Note:1. When using an extension cable to test the battery externally, the line resistance affects the internal resistance measurement, and the internal resistance test results do not have reference value. After the DIY, only one battery can be tested at a time, and it does not support testing multiple batteries simultaneously. The charging and discharging components are compatible with software algorithms and do not support retrofitting with discharge resistors. 2. During the charging and discharging process, some components may generate local high temperatures. Please ensure that the use environment is open and uncovered, and it is best to increase fan heat dissipation. Package List 1 x Battery Internal Resistance Tester