Hi
Not sure if there is an answer to this. My setup is a USB power bank as the main power supply and a LIPO battery to act as the UPS backstop when the power bank has fully discharged. The low voltage threshold is set to 3.2V but in my app code I say if the voltage reads 4V for more than 2 minutes to gracefully shutdown. If I then leave it 24 hours and connect a new fully charge USB Power bank I note that the Rpi draw goes significantly up by around 10mHa to recharge the LIPO battery. But, it has now been running for over 3 hours and still it says it is charging. Why does it take so long to recharge and at such high levels?
The recharge time mainly depends on the LiPo battery capacity and the actual charging current. Witty Pi 4 L3V7 can charge the LiPo battery with up to 1A current (controlled by the TP4056), but the current is not constant during the whole charging process. Near the end of charging, the charger enters the constant-voltage phase and the current gradually decreases, so the “charging” status may remain for quite a while even though the battery is already close to full.