15 Ampere Solar Charge Controller without Microcontroller

In the world of solar energy, a vital component in the charging process of batteries is the solar charge controller. This electronic device acts as a bridge between the solar panels and the battery, regulating the flow of charges and protecting against under and overvoltages. While many solar charge controllers utilize microcontrollers for efficient charging, there is a growing interest in simpler designs without the need for sophisticated programming. In this article, we will explore the fascinating world of a 15 Ampere solar charge controller that operates without a microcontroller. We will delve into the fundamental concepts, design considerations, selection process, and even provide a detailed circuit diagram for this elegant and straightforward solution. So, let’s embark on this enlightening journey and discover the wonders of a microcontroller-free solar charge controller.

15 Ampere solar charge controller without a microcontroller. In this article, you will learn the following things:

• What is a solar charge controller?
• How to design a solar charge controller?
• How to select a solar charge controller?
• Circuit diagram of 15A solar charge controller?
• Working of the solar charge controller.

What is a Solar Charge Controller?

Solar charge controller is an electronic device connected between the battery and solar panels. It is used to regulate the flow of charges from the solar panels to the battery. In other words, a solar charge controller is used to control the flow of charges from solar panels to the battery. It provides protection against an overflow of charges from the solar panels to the battery and is also used to protect batteries from under voltages. In essence, solar charge controllers provide protection against under and overvoltages of batteries during the charging and discharging process.

How to design a solar charge controller?

Many methods have been developed for solar charge controllers. There are various types of solar charge controllers available in the market, but mainly three types are commonly used.

1. Simple solar charge controller: This type of solar charge controller uses analog electronics to control the flow of charges.
2. PWM-based solar charge controllers: This type of solar charge controller uses microcontrollers to charge batteries through pulse width modulation methods.
3. MPPT solar charge controllers: MPPT stands for maximum power point tracking. This type of charge controller uses MPPT techniques to charge batteries from solar panels.

I have noticed that many people are searching on various websites about solar charge controllers, but they are not aware of the use of microcontrollers. It is important to note that high-rated solar charge controllers make use of microcontrollers. Therefore, I have decided to publish an article on a solar charge controller that does not require a microcontroller. In this article, I will be sharing the circuit diagram of a 15 Ampere solar charge controller that does not utilize any microcontroller. This circuit diagram is very straightforward and simple to understand.

How to Select a Solar Charge Controller?

Before making or purchasing any charge controller for your solar panels, a question may arise: what should be the rating of your charge controller? Let me provide you with an example to help answer this question. For instance, if you have 200-watt solar panels with an open-circuit voltage of 24 volts and a closed-circuit voltage of around 18 volts, you can calculate the rating of the required charge controller for your solar panel using a simple power formula. The power formula for DC power can be used to determine this.

P = V * I;

we know the values of power and voltage which is P = 200W and V = 18 V. By putting the above values in the power formula:

I = 200 / 18 = 11.11 Ampere

So, the calculated value of the current is 11.11A. Let’s suppose the voltage of the solar panels may decrease to a lower value, such as 15 volts. In that case, the current will increase. Therefore, it is recommended to select a charge controller that has a slightly higher value than the calculated one. I hope this clarifies your question on how to select a solar charge controller.

Circuit Diagram of 15A Solar Charge Controller

Circuit diagram of a 15A solar charge controller is shown below. If you want to use this circuit for a higher rating, you can use more than one solar charge controller in series to increase the current rating of the charge controller. The circuit diagram shown below is the simplest circuit diagram of a charge controller because it does not have any microcontroller. This circuit of the charge controller uses analog electronics instead of digital electronics.

Components list

Category,Reference,Value,Order Code
Resistors,"R1",4.7k,
Resistors,"R2",4.7k,
Resistors,"R3",10k,
Resistors,"R4",18k,
Resistors,"R5",100k,
Resistors,"R6",15k,
Resistors,"R7",12k,
Resistors,"R8",33k,
Resistors,"R9",22k,
Capacitors,"C1",2.2nF,
Capacitors,"C2",10uF,
Integrated Circuits,"U1",LM358,
Transistors,"Q1",RFP30P05,
Transistors,"Q2",BC337,
Diodes,"D1",LED,
Diodes,"D2",MBR1645,
Diodes,"D3",5.1V,
Miscellaneous,"J1",Solar panel,
Miscellaneous,"J2",BATTERY,
Miscellaneous,"RV1",5k,

Working of Solar Charge Controller

15-ampere charge controller circuit diagram uses analog electronic components to control the flow of charges from the solar panel to the battery. The RFP30P05 P-channel MOSFET is used to charge the battery. The RFP30P05 MOSFET has an approximate rating of 20A, meaning it can easily pass a current of up to 20 amperes. For more information, please refer to the datasheet of the RFP30P05.

The LM358 operational amplifier is utilized to turn the P-channel MOSFET on or off when the battery is charged up to 13.6 volts. When the battery reaches 13.6 volts, the LM358 turns off the MOSFET by providing a low signal to resistor R4. The LM358 is used as a comparator, comparing the battery voltage through voltage dividers connected to the inverting and non-inverting pins of the LM358 operational amplifier. Connect the solar panel to connector J1 and the battery terminals to connector J2. The LED D1 indicates the status of the charging process.

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