How to choose a solar charge controller

When choosing a charge controller, you must consider whether you will be using a PWM controller or an MPPT controller. An improper selection of a charge controller may cause the loss of solar power generation by up to 50%.

The choice of charge controller depends on the current of the solar cell array and the voltage of the solar system. Usually, you want to make sure that you have a charge controller large enough to handle the power and current generated by the panel. Generally, charge controllers have 12V, 24V, and 48 V. The rated current can be between 1 and 60 amperes, and the rated voltage can be between 6 and 60 volts. If you have not yet determined the size of the system or calculated your energy needs, we recommend you a solar panel calculator. It will help you determine the size of the solar panels and all other components in the system.

If your solar system has a voltage of 12 volts and your amperage is 13 amps, you need a solar charge controller with at least 13 amps. However, due to environmental factors, you need to consider an additional 25% so that the minimum amperage that the charger controller must have reached 16.25 amperes. Therefore, in this case, you need a 12V, 20A charge controller. Below are more details based on the type of charge controller installed in your system.

✈About PWM charge controller:

The PWM controller cannot limit its current output. They just use array current. Therefore, if the solar array can generate 50 amperes of current, and the charge controller you are using is only rated for 40 amperes, the controller may be damaged. It is important to ensure that your charge controller matches, is compatible with, and fits your panel in size.

When looking at the charging controller, you need to check its specifications or a series of contents in the label list. The PWM controller will have an ampere reading, such as a 30 ampere PWM controller. It indicates how many amps the controller can handle, which is 30 amps in the above case. Usually, you need to check the current intensity and rated voltage in the PWM controller.

(1) We want to check the nominal system voltage. It will tell us which battery pack voltage the controller is compatible with. For example, the nominal system voltage of the controller is compatible with 12V and 24V. In this case, you can use a 12V or 24V battery pack. Any higher value, such as a 48V battery pack, the controller will not work.

(2) Let's look at the rated current of the battery. Assume that in this example, you have a 30-amp rated charge controller. We recommend a safety factor of at least 1.25, which means you can multiply the current from the panel by 1.25 and compare it to 30 amps. For example, five 100-watt panels connected in parallel will be 5.5 x 5 = 27.5 amps. 27.5 amps x 1.25 = 34.375 amps, which is too much for the controller. It is because when the solar panel exposes to sunlight for more than 1000 Watts/㎡ or tilted, the panel may withstand a large current than the rated current.

  • We can check the maximum solar input. It will tell you what voltage can enter the controller. For example, you now have a controller in your hand, which cannot accept voltages exceeding 50 volts. Let us look at a panel with 2 x 100 watts in series, for a total of 21.6V (open circuit voltage) x 2 = 43.2 volts. In this case, the two panels can connect in series. Then we can use this controller.
  • Look at the battery type. It tells us which batteries are compatible with the charge controller. It is important to check this because you don't want the controller to be unable to charge the battery.

Our PWM controller is suitable for charging various lead-acid batteries (including unsealing, sealing, gel, etc.).

It can display charge/discharge parameters and effective battery charge management. And it also has a USB interface, which is more convenient to use.

✈ About the MPPT charge controller:

Since the MPPT controller limits its output, you can make an array as large as you need, and the controller will limit the output. However, if your panel is not used properly, it means that your system is not efficient. The MPPT controller will have an ampere reading, such as a 50-ampere MPPT controller. Even if your panel may generate a 90A current, in any case, the MPPT charge controller can only generate a 50A current.

The MPPT controller will have an ampere reading, such as a 50-ampere MPPT controller. They also have a voltage rating, but unlike PWM, the input voltage rating is much higher than the battery pack it will charge. It is because the MPPT controller has the special ability to reduce the voltage to the battery pack voltage and then increase the current to make up for the lost power. If you want to avoid series connections in small systems, you don't have to take advantage of high input voltage, but it is very beneficial in large systems.

We can check the maximum solar input voltage. For example, if the MPPT controller can accept a 100-volt input, then it will accept (up to) 100 volts and step down it to your 12V or 24V battery. Suppose you have 4 100 watt panels connected in series, and the open-circuit voltage of each panel is 21.6V. The 4 series connections will be 4 x 21.6 V = 86.4 V, and the controller can accept this voltage value.

✈ Can you use multiple charge controllers?

In the case that a single charge controller is not enough to handle the output of the solar panel array, you can use multiple charge controllers with one battery pack. In fact, for MPPT charge controllers, this may be the best way to connect to the system because the arrays have different maximum power points. Having two controllers can optimize the total power output.

However, if you use multiple controllers, we recommend using the same type of charging controller. So if you have an MPPT charge controller, all your charge controllers should be MPPT. In addition, you need to ensure that all controllers have the same battery setting input.

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