[Solved / Archived] Witty Pi 4 L3V7 and solar panel

There is no limit of battery capacity, however the charging chip TP4056 can only charge with up to 1A current so it will take long time to charge a very big battery.

You can charge the battery with solar panel, but the charging voltage source will also feed to the DC/DC converter, which is MP3423 and it accepts only up to 5.5V. Even after considering the voltage drop on an SS54 diode, it is still not safe to feed the device with 6V.

Thanks a lot for answering.

Am I right to say that with a solar panel connected to the USB port there is no way to check the battery level? The only way is to disconnect the solar panel or wait until the current provided by the panel is not enough and the witty pi turns to the battery?

@marcot77 yes, it is not possible to measure the battery voltage when it is being charged.

Considering that my solar panel will never produce enough current to power my system, can I expect the solar to power the charging circuit when the pi is off and run always on battery when is on allowing me to monitor the battery voltage? In other words, if the current produced but the solar panel is not enough, will the witty pi turn to battery monde even if the input voltage from the panel is 5V?

@marcot77 the short answer is no. Witty Pi 4 L3V7 switches the power path base on the voltage on USB-C connector, it doesn't know if that power source is good enough to power a Pi.

You may consider implementing your own charging circuit and integrate it with Witty Pi 4 Mini instead. That way you may always monitor the voltage of battery (via the VIN pin).