Hi everyone

So this is a circuit of a charge regulator for solar panels. the aim is to charge the battery with 14V then 13V after a moment before its totaly charged. To do so we will need the PWM of arduino to open the MOSFET when the voltae of solar pannel is higer then the battery's then when its opposite arduino shut down the mosfet. the zener diode is here to limit the voltage to 15V.

so what do you think ? is there something to correct ?

 

As I understand your circuit, you don’t need either diode. They waste a lot of power, so it’s good to get rid of them.

The MOSFET should probably be between the battery and ground to control the low side rather than the high side as you’ve shown. It will be easier to get the gate voltage right.

 

If you don't use a regulator on a 20W panel, you will either boil the battery or damage it.

 

Have a read up on this...https://create.arduino.cc/projecthub/abhi_verma/arduino-pv-mppt-solar-charger-371474

There are more, like....
http://www.instructables.com/id/ARDUINO-SOLAR-CHARGE-CONTROLLER-Version-30/
It may give you some help.
He does say this actual one does not work but there is info.
A Google search will find lots more.

 

If you don't use a regulator on a 20W panel, you will either boil the battery or damage it.

Adding to that point, the panel voltage is far less interesting than the current flowing into the battery. I'd consider using the Arduino to monitor that, or just use a dedicated charge controller IC.

 

Without Arduino it works. As an option.