Solar charge controller without microcontroller

What is solar charge controller?

Solar charge controller ( for example: RENOGY 40 AMP MPPT CHARGE CONTROLLER )

is an electronics device connected between battery and solar panels. It is used to regulate charges flow from solar panels towards battery. In other words solar charge controller is used to control flow of charges from solar panels to battery. It provide protection from overflow of charges from solar panels to battery and it is also used to protect batteries from under voltages. Its mean solar charge controllers provide protection against under and over voltages of batteries in charging and discharging of batteries.

How to design solar charge controller ?

Many methods have been developed for solar charge controllers. Many types of solar cvharge controllers are available in market. But mainly three type of solar charge controllers are used.
Simple solar charge controller: This type of solar charge controllers use analog electronics to control flow of charges.
PWM based solar charge controllers: This type of solar charge controllers used microcontrollers to charge batteries through pulse width modulation method.
MPPT solar charge controllers: MPPT stands for maximum power point tracking. This type of charge controller used MPPT techniques to charge battery from solar panels.

I have seen many people searching on different websites about solar charge controllers. But they don’t know about use of microcontrollers. All high rating solar charge controllers use microcontrollers. So I decided to post an articles on solar charge controller without microcontroller. In this article I am going to post a circuit diagram of 15 Ampere solar charge controller which do not use any microcontroller. This is very simple circuit diagram of charge controllers.
How to select solar charge controller ?

Before making or purchasing any charge controller for your solar panels, the question must come into your mind. What should be the rating of your charge controller? Let me give you one example, after this example you will get th answer of this question. For example you have 200 watt solar panels which have open-circuit voltage of 24volt and closed circuit voltage would be around 18 volt. By using simple power formula you can calculate rating of required charge controller for your solar panel. You know about power formula for DC power that is we know the values of power and voltage which is P = 200W and V = 18 V. By putting above values in power formula:

I = 200 / 18 = 11.11 Ampere

So calculated value of current is 11.11A. Lets suppose voltage of solar panels may reduce to lower value 15 volt. In that case current will increase. So you should select charge controller of little higher value than calculated. I hope you got the answer of question “How to select solar charge controller”.
Circuit diagram of 15A solar charge controller :

Circuit diagram of 15A solar charge controller is shown below. If you want to use this circuit for higher rating, you can use more than one solar charge controller in series to increase current rating of charge controller. Circuit diagram shown below is simplest circuit diagram of charge controller. Because It do not have any microcontroller. This circuit of charge controller used analog electronics instead of digital electronics.