I need some help regarding my project. I have made a dog feeder with Arduino Uno, which is powered with a 3000mAh Li-Ion battery. I want the system to be charged with a solar panel (more solar panels can be wired in parallel to increase current output), so I am using THIS module. However, I need load-sharing based on this thread. My example circuit is the following

I need help choosing the P-Mosfet. I want the mosfet to be ON when the voltage from the solar panel drops below 4.4V, thus allowing the load to use the battery as a power source and the mosfet to be OFF when I have above 4.4V, so that it will charge the li-ion and power to load.

  1. Correct me if I am wrong, do I need VGSth to be minimum -0.6V to turn ON the mosfet, when the voltage at GATE drops to 4.4V (4.4V - 5V at SOURCE = -0.6V )? I am thinking of THIS if so.
  2. Can I use a silicone diode instead of a schottky like 1N4007, in order to drop the voltage at the load with -0.7V ensuring that I won't fry the Arduino and the other 5V peripherals such as 16x2 LCD Display, when the solar voltage is higher than 5V? The issue is then just before the solar voltage at the GATE to drop to 4.4V to turn ON the mosfet, the voltage at the load won't be enough to power the arduino ( lets say the Vsolar is 4.6V - 0.7V from the diode = 3.9V )
  3. The the other option I am thinking of that could be much easier to implement is to measure the Vsolar from the Arduino's analog pin and when it drops below 4.4V to turn ON a logic level P-Mosfet and possible another P-Mosfet (switched ON by the Arduino) to allow the Vsolar to go through MT3608 booster when the voltage is less than 5V in order to power the load. Can this work ? I have found that the same thing was asked for the same charge IC (CN3609) in this thread and the solution is to use a comparator, but if the Arduino voltage measure at the analog pin can be implemented wouldn't it be much easier overall?

I would really appreciate your suggestions on how I can achieve the load-sharing with the solar panel!


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