Features Battery Connection: The positive pole of the battery is connected to B+, and the negative pole of the battery is connected to B-. The mobile power module can be connected to one lithium battery or multiple lithium batteries in parallel. But the following conditions must be met: capacity≤20W mAh, 3-4.2V voltage. Output Load Indication: After the DIY USB mobile power module is connected to the load, long press the LED switch to start output. Then the screen will display the word "OUT" and the output voltage/current 5V/1A or 5V/2.1A. Protection Function: The mobile power charging protector integrates the protection circuit of the boosted lithium battery to prevent over-discharge, over-charge, overload, short-circuit protection, over-current protection, and over-temperature protection. Charging Indication: The LCD screen of the dual USB mobile power charging protection module displays the word "IN" when charging, which is easy to use. Specially designed for 186 50 battery DIY power bank. Intimate Service: We provide 7-day worry-free return and exchange service for all customers. If you have any questions about our mobile power modules, you are welcome to contact us and we will serve you wholeheartedly. Specification: Size: 58*27*15mm / 2.28*1.06*0.59in Weight: Approx. 13g   Package list: 1 x Dual USB Power Bank Module   Note: Please do not reverse the polarity connection of lithium battery, or the battery will burn out! Package List