we are trying to power a smartphone using the Otii Arc + the suggested external power supply. The smartphone is an old Nexus 5.
Following some documents and tutorials, we removed the battery and added 7 capacitors close to the battery circuit.
The 7 capacitors are 100uF each:
The Nexus 5 is known to work when using external power instead of a battery, as shown here:
The original battery is 3.8 V. We used the Otii Arc to provide 4.1 v to simulate a fully charged battery.
In this condition, the boot phase does not start.
We then tried to provide additional power also using the USB connector of the smartphone, using a common smartphone charger. In this case, the boot phase starts. We can see the boot phase proceeding for 5-6 seconds, then it stops abruptly.
Do you have any suggestions? Is there anything we can do to better understand what is the problem?
First is regarding the connection to the phone
In the tutorial you linked, they still use the battery-PCBA, and connect the power supply to the connection points on the PCBA where the battery cell is connected. Is your connection the same? I still believe that you need this PCBA in your connection.
My second comment is how does your measurement look like when the phone stops, is it a drop in voltage at the same time, then I believe you need more capacitance and/or thicker and shorter cable.
Last, you can get information from the phone by fetching the ADB logs. Look in a tutorial how you can access the ADB log file and read that for when the phone hangs, you probably have some good information there.