What is a solar charge controller used for? The charge controller or charge regulator is placed between your solar system and your battery storage. Its characteristics must therefore match your off grid solar system on one side and your battery storage on the other. This often makes the right choice a bit complicated. Here is our guide and helpful tips to help you make the right choice!
MPPT or PWM solar charge controller?
A PWM controller is much more limiting than the MPPT controller. While it has the advantage of being cheaper, it can only work with a single panel of 36 cells and 12V or a single panel of 72 cells and 24V (or 2 panels of 12V in series) with relatively low power. Also, you need a 12V panel for a 12V battery and a 24V panel for a 24V battery.
The MPPT controller is much easier to use. It can accommodate multiple solar panels in parallel or in series, depending on the cumulative clamping voltage (Voc) and short circuit current (Isc) of the solar panels. It optimally utilizes the capacities of your solar system thanks to advanced technology to offer you better yields. The MPPT thus allows you to recharge a battery with a solar system with a higher voltage.
Statement from Orangemarine :
We recommend that you choose a more efficient and tolerant MPPT charge controller. PWM controllers are less efficient and are only suitable for a specific installation.
What is a charge controller used for?
The charge controller allows you to make the connection between your power generation source (solar panel, wind turbine, solar generator) and your battery storage. Its role is to protect the battery from charging current that is too high or too low, and to protect your power generator from reverse flows. Depending on the model, the charge controller can also convert the generator voltage to a voltage suitable for the battery storage.
The charge controller stops charging when the batteries are fully charged and discharges the excess energy by converting it to heat. Depending on the model, it can also analyze the state of charge of your battery storage and, if necessary, cut off the charging current earlier, so that the battery is charged to 100% about once a week.
These charge controllers allow you to make better use of your generator and protect both the power station and your solar backup generator. For wind turbines and hydro generators, there is usually a recommended charge controller that is perfect for your model. For solar panels, the choice can sometimes be a bit more difficult.
How do you choose the right charge controller for your solar system?
In this case, you already have one or more solar panels or you already know which solar panel(s) you want to buy. Then you need to choose the charge controller that is best for you. If you already have a battery and want to connect your solar system to it, this guide to choosing the charge controller that best fits your solar panel battery storage is the one for you.
Installation with a single solar panel:
Choosing a charge controller for a single solar panel is quite simple. In fact, there are only two values to consider: The clamping voltage (Voc) and the short-circuit current (Isc). You can find this information in the product data sheet, in the product manual or directly on the solar panel. It is imperative that the clamping voltage (Voc) and short circuit current (Isc) are 10% below the maximum accepted by the charge controller.
For an installation with multiple solar panels:
If you have multiple monocrystalline solar panels, choosing the right charge controller is a bit more complex. Initially, the values to consider are always the same: The clamping voltage (Voc) and the short-circuit current (Isc), which you will always find on the product sheet, in the manual or directly on the solar panels. However, these values are adjusted accordingly depending on the connection type and number of solar panels.
In electrical engineering there are 3 types of circuits:
The parallel connection, that is, currents in amperes (A) are added.
The series connection, i.e. voltages in volts (V) are added.
The hybrid circuit with solar panels connected in series and parallel.
Here, the clamping voltage (Voc) is affected for a series connection and for a hybrid connection. The short circuit current (Isc) is affected by a parallel connection and a hybrid connection.
The open terminal voltage (Voc):
It is imperative that the open terminal voltage of your solar system is 10% lower than the maximum voltage accepted by the charge controller. For parallel connections, it is not affected by the number of panels and is accepted by the majority of MPPT charge controllers, you can learn more about the difference between series and parallel battery. On the other hand, for series connections, the clamp voltage (Voc) of each solar panel must be added and the sum of the clamp voltages must be accepted by the charge controller. If this is not the case, a charge controller must be selected that accepts a higher clamp voltage from the solar system. Example: 6 solar panels connected in series with 12V and a terminal voltage (Voc) of 19V:
The short circuit current (Isc):
The short circuit current of your solar panel must be 10% lower than the maximum value accepted by the charge controller. When connected in series, the short circuit current is not affected by the number of panels and is accepted by the majority of MPPT charge controllers. On the other hand, when connected in parallel, the short circuit current (Isc) of each solar panel must be added and it must be checked if the sum of the short circuit currents is accepted by the charge controller. If this is not the case, a charge controller must be selected that accepts a higher short-circuit current from the solar system. Example: 6 solar panels with 12V and a short circuit current (Isc) of 6A in parallel connection. Please note: To maximize the capacity of your solar system, you will need a battery large enough to store the power generated. Therefore, once you have decided on a solar panel and a charge controller, you should check that your battery is also suitable. To do this, the voltage of your battery must match the charge voltage of the charge controller. In addition, the charge current of the charge controller must be between 10% and 20% of the capacity in Ah of your battery, as with a charger. For 12 volt lithium battery, this can be up to 30% of the capacity.
Renogy’s Tip about choose solar charge controller:
The hybrid circuit with some panels in parallel and others in series is most important if you have many solar panels. This way you will find a balance between increasing the cumulative clamping voltage (Voc) and increasing the cumulative short circuit current (Isc). In this way, you can make the best use of your charge controller and opt for a lower-cost, lower-capacity model.
Example: You have 6 solar panels with a clamping voltage (Voc) of 19 V and a short-circuit current (Isc) of 6 A. You can connect your solar panels so that you have 5 in series and 1 in parallel, or 4 in series and 2 in parallel, and so on, up to 1 in series and 5 in parallel. To calculate the voltage and current of your system, you need to sum all the clamp voltages (Voc) of the panels connected in series to determine the cumulative clamp voltage and add the short circuit currents (Isc) of the panels connected in parallel to get the cumulative short circuit current of the solar system.
So, for a combination of 3 modules in series and 3 modules connected in parallel, the calculation is: 19 + 19 + 19 = 57 V on one side and 6 + 6 + 6 = 18 A on the other side. With such a circuit you ideally need a charge controller that accepts a cumulative clamping voltage of at least 65 V and a cumulative short circuit current of at least 21 A.
Here you will find our full range of rigid and flexible solar modules, as well as our guide and helpful tips for selecting a solar module. Find our guide and helpful tips for selecting a marine battery here. Realize your wiring work with our power cables, and thanks to our renogy’s guide and advice, choose the right type of cable you should choose for an electrical installation.