What size charge controller for 1200W solar panel?
The charge controller can take a range of voltages and amperages, and slam that variable power, cleanly back into the box. Batteries are designed to be charged in fairly tight voltage and amperage ranges to protect the materials inside, and the controller does this job. Apply too much power and you cook the inside of the battery. Apply too little power and the battery will not charge.
The charge controller takes the power from a solar panel installation, and pushes it into the battery bank at the right levels.
Therefore, you will usually want to make sure that you will get a charger controller that is large enough to handle the current and voltage produced by 1200W solar panel system.
The charge current rating for the controller that you need for your 1200W solar panel system, it can range between 30 and 100 amps, and maximum input voltage from 100 to 250 volts.
To determine the size of the charger controller for 1200W solar panel system, for a 24V system, divide the power output of the array (1200W) by the nominal system (Battery) voltage (24V), to give you 50 Amps. This means you will need a 50A charge controller for your system.
However, the rated charge current is not the only thing to consider, but also the configuration of your solar panels.
Keep in mind that this will be different for a 12V system or other system voltages and the voltage of the individual panels.
What size charge controller do I need for 1200 watts?
Determining the size of the charge controller that is appropriate for your solar array system depends on two factors: the system (battery bank) voltage and the configuration of solar panels, and not only on the wattage of your solar array.
Each charge controller has its own characteristics, and the most important thing to consider when buying one is the charging current and the maximum input voltage and current.
Maximum PV input voltage: is the maximum voltage coming from the solar arrays that the controller can tolerate and must not be exceeded
Maximum PV short circuit current: is the maximum current coming from the solar arrays that the controller can tolerate and must not be exceeded
Steps to calculate the size of the charge controller for 1200 watts?
1. Determining the system voltage
You should choose the battery bank voltage you want (12V or 24V). It would be better to work with a 24V system because in this case, you will need a smaller and cheaper charge controller. Also, the wire size from controller to batteries will be thinner than in a 12V system.
Getting a 24V battery bank is not difficult; if you already have 12V batteries, all you have to do is connect each pair of batteries in series. The problem in this case is that you will need an inverter that operates with a 24V battery bank system, which is more expensive than a 12V inverter.
Therefore, if you already have a 12V inverter, you will need a 12V battery bank.
So, indirectly the inverter voltage is what will determine the size of the controller you should use.
Once you have decided on the system voltage, here is how the rated charge current of the controller that you should choose with 1200W solar array will look like:
Charging current = Size of the solar array (wattage) / Nominal System (Battery) Voltage.
- For 12V system
For a 12V system, the rated charge current of the charge controller should be at least 100A
- For 24V system
For a 24V system, the rated charge current of the charge controller should be at least 50A.
2. Determining the configuration of you solar array
The next step is to determine the maximum PV input voltage that the controller you choose can handle (75 volts - 100 volts - 150 volts). What controls this choice are the characteristics of your solar panels and how you plan to wire these panels (in series, in parallel, or a mix of series-parallel connection).
- When connecting the panels in series, the total voltage adds up. Therefore, it is important to ensure that the total voltage of the solar system does not exceed the maximum solar input voltage of the charger controller.
- When connecting the panels in parallel, the total currant adds up. Therefore, it is important to ensure that the total PV short circuit current does not exceed the maximum solar input current that the charger controller can handle.
For example: If we consider using solar panels with specifications of 200 watt each, we would need six panels to provide 1,200 watts total, Considering the electrical characteristics of these panels at a solar panel temperature of 25°C:
- Voc = 24.5V, Isc = 10.6A
- Vmp = 20.2V, Imp = 9.91A
If we connect all six panels in series (6S configuration), the total open circuit voltage of the array at 25°C would be:
- Vmax array (25°C) = Voc * Number of panels in series
- Varray(25°C) = 24.5V * 6 panels = 147 V
In this case, when 6 x 200W solar panels (1200W) are wired in series we would need a 150V|100A charger controller for a 12V system, or a 150V|50A charger controller for a 24V system.
Cold days make solar panels and wires work "REALLY WELL" and can overload the system: When temperatures drop to low levels, the temperature of the panels can decrease to below 25°C. In this case, if there are connection problems, the voltage of the array may exceed 150 volts, which should be avoided. In such a case, it is best to wired these panels in 3S2P configuration (combine a pair of string in parallel, with each string consisting of three panels connected in series).
In this configuration, the maximum voltage of the array at 25°C would be:
- Vmax array(25°C) = Voc * 3
- Vmax array(25°C) = 73.5V
The maximum short circuit current of solar arrays would be:
- Imax array = Isc * Number of string in parallel
- Imax array = 10.6A * 2 strings = 21.2A
In this case, when 6 x 200W solar panels (1200W) are wired in 3S2P configuration we would need a 100V|100A charger controller for a 12V system, or a 100V|50A charger controller for a 24V system.
In terms of cost, a 100|100A charger controller would be cheaper than a 150|100A charger controller, and the same goes for the 50A charger controllers.
Can I use multiple controllers for 1200W solar array
Yes, if you already have a small charger controller, you can add another charger controller and divide 1200W of solar panels among multiple controllers. However, you must ensure that the output voltage of each charger controller is the same and compatible with the battery bank.
If you need further clarification on this topic, please refer to our article on connecting multiple charger controllers to one battery bank.
Can I add more controllers when I add too many panels?
Yes, If you've already reached the maximum amperage rating of your charge controller, adding another controller and connecting them in parallel can help manage the load from too many solar panels.
This can be a cost-effective solution compared to upgrading to a larger or more expensive controller. Just make sure to properly size and configure the new controller to work in parallel with your existing setup.
Conclusion
When it comes to charge controller sizing, you have to take into consideration whether you’re using a 12V system (12V battery bank + 12V Inverter ) or 24V system (24V battery bank + 24V Inverter).
However, when choosing a solar charge controller you should also consider the configuration of you solar panels. If the panels are connected in series, the total voltage of the array must be less than the maximum input voltage of the controller. If they are connected in parallel, the total current from the solar array must not exceed the maximum input current that the controller can handle.
Therefore, to calculating the size of controller you need for 1200w solar panels, divide this amount of power by your battery bank voltage.
A higher voltage battery bank will be better because the charging current reduces. A controller with a lower rate charge current is cheaper.
Mohamed Bellamine
I'm the blogger behind Goo SolarPower. As a solar engineer, and a strong supporter of renewable energy. I've always been interested in Solar devices. I loves to write articles, guides, and tutorials about solar PV technology. Through goosolarpower.com I want to help people build and understand how solar power systems work.