Fit for 1~6 cell battery pack. Monitor the voltage of each cell. If your charger is serial charge mode, you can use the checker to monitor the cell voltage. To make sure the status of any cells are no over-charge.
You can use the checker to test you battery.
Or you can use the checker to know is your battery pack fit for your power system or the healthy status of each cell.
Just connect your battery and the checker to your airplane/heli. If the voltage of any cell go down very fast even lower than 3.3v when the battery have loading, that's mean the battery loading to large or the pack maybe broken.