G.T.Power Portable 5V 1000mA 2-6S Li-Po to USB Battery Charger - Black
Battery meter voltage precision: +0.01V~-0.01V; Test for 1-6S Li-Po/ Li-ion/ Li-Mn/ Li-Fe battery; The USB output will be cut off automatically if any battery's voltage is lower than 3.0V and at the same time the LED tube will display "SOP".