Solar System Pakistan

Solar Charge Controllers

It is a small electronic device which you need to connect between your Solar PV Panels and your battery. The DC voltage produced by the solar panels is not uniform throughout the day. It fluctuates continuously due to various reasons. For example, sun ray intensity, passing clouds, rains, shadow, birds or many other factors. Even varying temperature throughout the day and climatic seasons also largely affects the voltage production rate.

However, your battery needs a precise range of voltage and ampere to recharge the cells. Supplying over or under feeds to battery affects the battery life and performance. So it protects your batteries from overcharging. In fact you will not be able to use the electricity if you draw it directly from panels. Because your connected load will also continuously fluctuate to perform. If you connect a LED bulb, it will flicker. If you connect a fan, the speed will be varying. And also life of the loads will reduce.

Hence, a solar charge controller receives the current produced by the solar panels. It regulates the voltage to a constant specific voltage and current, forwards it to output for the battery charging. It also gives the regulated 12V DC/24V DC (as per the specification) and regulated ampere for the load output. The regulated voltage is given to Load output fully when the connected battery is fully charged. The inbuilt logic decides to pass very minimum current to a fully charged battery. It is just to maintain the float charge of the battery. Rest entire supply is given to the Load output. All such calculations happen automatically inside the charge controller through a logic board.

Types of Charge Controllers

Solar Charge Controllers are mainly of two types. The classification is based on the built technology of the controller.

(A) PWM Type
(B) MPPT Type

However both can be connected with any systems and fully interchangeable with each other. The difference between these are the working logics. PWM technology is little outdated now, while MPPT is the newer one and much more efficient. MPPT controllers can extract more electricity from your same solar panels than a PWM controller under same set of external conditions. MPPT controllers are about 2 to 2.5 times costlier than a PWM controller. However this initial little bit extra investment can help you to save more money on longer time through the additional electricity you will generate from your solar systems.

Selection Parameter of Charge Controller

Solar charge controllers are basically classified with two parameters – Voltage & Ampere. First you need to understand what is your solar system voltage. If it is a 12V system, then you have to buy a 12V controller. Similarly, for a 24V system, the controller has to be 24V too. Once the voltage is finalized, then comes the play of how much ampere you will need. Therefore, you will need to add the output currents (if the panels are connected in parallel) of all the solar panels which you will connect with this controller. Alternatively, if the panels are connected in series, then the Ampere will be for any one panel (the highest among the 3 panels you have). You will find a specification sticker behind every solar panel plates. Check out my article on solar panel for the details. After adding up all the Ampere values (for parallel), you will need to select the next higher standard Ampere of the controller.

For example, consider that you have 3 panels of 100 watts each. Now rated max output current (“Imp”) of these 3 panels are 9.81, 9.50 & 8.85 Amps. Then total of the current value is (9.81+9.50+8.85) = 28.16 Amp for a parallel connection. For a series connection the current will be 9.81 Amp (being the highest among the 3 panels). The standard ratings available in the market are 6 Amp, 10 Amp, 20 Amp, 30 Amp, 40 Amp… this. So in this example you will need to get a 30 Amp or 40 Amp charge controller if you are connecting your panels in parallel. The same would be 20 Amps in the case of Series connection. Keep it a note that there is no harm in taking higher Amps but you can not use a lower Amp rated controller. Also the price of the controller keeps on increasing as you go higher in Ampere rating. So you will need to balance it while purchasing a charge controller for your system.

Solar Charge Controller Connection Diagram

Solar charge controller connection is very easy. Basically there are 3 sections – (A) Input from Solar Panel, (B) Battery connection & (C) Output Load. You need to just fix both positive and negative wires in each section as per the (+) and (-) polarity. Please refer the below image for better understanding.