Tenergy Compact Cell Meter - LiPo Alarm and Digital Battery Checker for LiPo LiFePO4 Li-ion NiMH NiCd Battery Packs Digital Battery Checker For 4S-12S NiMH/NiCd battery packs, Tenergy Compact Cell Meter can display total voltage. For 1S-6S LiPo/LiFePO4/Li-ion battery pack, it can display: total battery voltage, individual cell voltage and the difference between the highest and the lowest individual cell voltage Battery Alarm For lithium-based batteries, Tenergy Compact Cell Meter can be used as an over-charging / over-discharging alarm. It emits a loud beeping sound and its LED flashes brightly when the batterys voltage rises above 4.22V, or drops below an adjustable threshold between 3.0V and 4.0V. Flight Time Tracker With Tenergy Compact Cell Meters lightweight and compact design, you can mount the unit on your RC helicopter/plane, and during its flight the alarm can inform you when the battery is in need of charging. Easy To Use Tenergy Compact Cell Meter can read the status of your battery automatically as soon as they are connected. Its simple control makes it suitable for users at all levels. LCD screen Easy-to-read LCD screen lets you view your batterys status at a glance.