... circuit, lightning protection, etc function. Easy to use:1, Charge the power bank 1-1, use USB cable & a USB adaptor or use laptop ... about it in advance)3-1, press down the switch to light the LED indicator, you will find the capacity shows 25%-75%-100 ... . (please refer to the picture below, select 1 ~ 6 connectors which you need) Attention:1, before using, please do charge the power bank over 9 ...