Universal Lithium single cell charger PCB. Connect 4 to 16V input, such as solar cell either through PV input solder pads, or plug in through K1 jack. USB jack for alternate charging (limited to 500ma). Note you can use K1 with USB charger for fast charging up to 2A. Connect battery to +BAT- terminals. USBOUT is default 5V 2A output, but you can change jumper for 12V output. Output can also be customized with resistor change R9. LEDs indicate when charging, CHG LED goes out after charge complete. See also 5V 2A power supply for fast charging.