Functional but glitchy
Most features work for one battery, but another battery cannot be renamed, no cell voltages, no history. The app seems to hang often, and constantly pops up a dialog if we temporarily jump over to another app. Annoying.
Not enough ratings yet to assess Power.
Power-Sonic Lithium appears to be a legitimate app. AppsHunter Legitimacy Score for Power is 80/100.
Based on 80 of 100 points across 7 verification signals from App Store and developer data.