Adafruit MAX17048 LiPoly / LiIon Fuel Gauge and Battery Monitor - STEMMA JST PH & QT / QwiicLow cost Lithium Polymer batteries have revolutionized electronics they're thin, they're light, they can be regulated down to 3. 3V and they're easy to charge. On your phone, there's a little image of a battery cell that tells you the percentage of charge so you know when you absolutely need to plug it in and when you can stay untethered. The Adafruit MAX17048 LiPoly LiIon Fuel Gauge and Battery Monitor does the same thing. Connect it to your Lipoly