This is the Great Planes Pro Series Lithium Voltmeter LVM 2-6S.
Measures and displays individual cell voltages and overall pack voltage of 2-6S Lithium Polymer (LiPo), Lithium Iron Phosphate (LiFe) and Lithium Ion (Li-Ion) batteries on an LED display 6S in-line adapter for FlightPower and Thunder Power batteries Loop on end allows easy attachment to a wrist strap, neck strap or keychain
Great Planes Pro Series Lithium Voltmeter with 6S in-line adapter
Plugging in battery