[SOLVED] Arduino Solar Charger Controller voltage problem

Hello all, I am trying to make solar charge controller using arduino. I am able to read exact volts of solar and battery voltage and I am also able to charge the battery. Problem occurs when I the battery is charged because the charging do not stop.
For ex solar volt is 13.5 and battery at present is 11v. As soon as I start charging the battery is connected to solar so now if I read the battery volts (during charging) it will be higher than 11v (around 12v). So lets say if threshold value for over charging is 13v so it will start charging and when it reaches 13v it will stop charging. Now in this condition (during no charging) it will read the actual battery voltage which will be around 12v, again less than 13v so it will again start charging.
This will keep on going. Because we can not read the actual battery voltage level during charging, as during charging it will show the solar voltage. So how to handle this situation.

For ex: (threshold voltage for over charge is 13.0v)

Solar Volt: 13.5 Battery Volt: 12.9 --> battery is at 12.9v
Solar Volt: 13.5 Battery Volt: 13.0 --> battery has charged to 13.0, charging will stop
Solar Volt: 13.5 Battery Volt: 12.2 --> During no charging. arduino reads the actual voltage, as it is low it will again start charging.
Solar Volt: 13.5 Battery Volt: 12.8 --> battery charging
Solar Volt: 13.5 Battery Volt: 12.9 --> battery charging
Solar Volt: 13.5 Battery Volt: 13.0 --> battery charged, stop charging, again it will read exact volts
Solar Volt: 13.5 Battery Volt: 12.2 --> battery starts charging.

I hope I have explained my query clearly. Please anyone help me here. I am attaching the schematic of the circuit I am using

The aim is to prevent the battery going over 14.4V, and to prevent 'gassing' (bubbling electrolyte). Battery voltage is elevated during a charge. Afterward it takes several hours to settle down to its resting voltage, 12.8 V.

A taper charge is optimum. Start to reduce charge rate when battery reads 13.5V. Reduce steadily until final voltage is 14.4V. Then charging ends.

As an easy substitute, I designed my homebrew charge controller to operate on hysteresis. An op amp controls a mosfet.
(a) Mosfet is turned full On.
(b) Charge battery until it reads 14.4V.
(c) Shut off mosfet.
(d) Battery voltage settles back to 13.4V or so.
(e) Turn on mosfet. Repeat above steps for remainder of charge session. On cycles get shorter, Off cycles get longer. This schedule allows the battery to charge until it is full.

Hi BradtheRad
Till now I was confused why everyone is using PWM to charge batteries. Now its clear. Thank You. I will follow the steps you mentioned, and will tell you about it.