I have a 12 V 7 Ah battery. In order to charge a battery, we need to supply the voltage greater than the voltage of battery. Now lets say I have a power supply which is giving 14 V and battery current status is 12 V. When I will plug in the power supply pins to the battery, the battery voltage will reach upto 14 V and battery will start charging.
Now I have a solar charge controller PCB where I am using solar panel to charge the battery. Below is its schematic:
In the above image,
X1 is the connector where will connect solar panel. A microcontroller is used to read the solar voltage through voltage divider circuit.
CHARGEPIN is the pin which is used to enable the charging of battery.
So lets we have a full sunlight and solar output is 18 V. Now the problem I am facing is as soon as I connect the solar panel and start the charging, the voltage of solar panel reduces to 13 V but in the above case where I was using a power supply, the voltage didn't drop. It was same (power supply voltage was still 14 V). Because of this scenario, the battery is taking too long to charge.
Is the schematic wrong? Am I missing something?