Can you power a smartphone (no battery at all) by a power supply
$begingroup$ I modified an old smartphone (Oppo Find 5) to work directly from a USB power supply by connecting the battery contacts to 5 V directly or via a diode to lower the voltage slightly. That works for that model phone. There is no guarantee that this will work for other phones as well! In the end, you will just have to try what works. Some phones need a lot