Features: The 2 series lithium battery boost charging board is double link series lithium battery synchronous boost charging module High quality material with high integration and high reliability. The charging efficiency is 94% at the input voltage of 5V, bat voltage 8.4v and charging current of 1.2A. Charging integrates various protection functions: input overvoltage, input undervoltage, output overvoltage, output short circuit, chip over temperature, and maximum charging time of 24 hours. The no-load voltage of the module is 4.3V, which can only be increased to 8.4V after two lithium batteries are connected Specifications: Working Range of input voltage: 4.6v-5.5v 5V/2A input synchronous boost charging Input adaptive charging Support two 4.2V batteries Ed- displays the charging status, and supports the display of two color lights Self contained trickle / constant current / constant voltage charging mode 24 hour time- out protection for charging Output over current, over voltage and short circuit protection Input over voltage and undervoltage protection Input voltage withstand voltage 13V OTP- over temperature protection Length: approx 28mm/1.1in Package Includes: 1PC USB Charging Module note: Due to the different monitor and light effect, the actual color of the item might be slightly different from the color showed on the pictures. Thank you! Please allow 1-3mm measuring deviation due to manual measurement.