How to Choose the Right Solar Charge Controller

Posted on : 09-02-2014 | By : Max | In : DIY Solar

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GUIDE: How To Make a DIY Solar Power System At Home

Solar Charge Controller

A solar charge controller is used to regulate the energy flow for many home solar inverter systems as well as some PV hybrid systems. The solar charge controller is the most critical unit of this process, so selecting the right one is crucial in determining the efficiency of your system.

While the charger itself is roughly 5% of the total cost of the system, it controls the power management of the batteries which means it extends their life and reduces the associated costs with running the solar power system. When running an off grid solar power unit, having a solar charge controller is crucial in extending the life of the battery bank.

What a Solar Charge Controller Does

Basically, the solar charge controller has two functions:
- Prevents the batteries from deep discharging
- Protects the batteries from overcharging
Inside solar charge controllers are the “state of charge calculation (SOC) that monitors the status of the battery. The essence of what a solar charge controller does is to effectively manage the battery so you get the right amount of power needed at all times.

Good solar charge controllers are low consumption units, they are protected by tough, durable casing and feature large connection terminals. Also, they feature a user-friendly display that instantly indicates the status of the all the systems connected. So no matter your understanding of solar power, all the information displayed is easy to comprehend.

How to Choose a Solar Charge Controller

Amperage & Power: Basically, once you know the size of the battery, the size of the solar array connected to the battery and the load schedule, then you can determine the amperage of the solar charge controller that you need.

There are amperage options for MPPT charge controller that offer ranges from 20Adc up to 80Adc. They can be run from parallel systems that offer more than 80Adc as well.

Voltage of the System: This is not array voltage, but the voltage of the system itself which includes the battery and inverter interaction. System voltage options are generally between 12 to 60Vdc. Most default systems are set for 48V for the modern MPPT charge controllers.

Array Voltage: This is the open circuit voltage for the PV array taken at the lowest recorded temperature. Most of these are limited by 150Vdc, so you will want one that converts up to 12Vdc as well. The distance between the batteries and the array plays a large factor here as well, so you need to know the distance.

Important Considerations for your Solar Charge Controller

In addition to the information presented, there are also a number of different elements you will need to consider as well. This is so you could get the best controller while balancing out the needs of your system. What follows are the considerations you will have to make as to the specificity of your solar panel system.

Shunt Controllers: This is the most efficient and common topology used in solar charge controllers. This uses a pulse-width modulated short circuit applied to the module of the solar unit so that it can regulate the energy flow. Because of the high resistance found in solar modules, the use of shunts can be accomplished with no side effects. Having shunt controllers as part of your overall system can assist your solar charge controller as well in handling your power requirements.

DC to DC Converter: These are controllers with integrated DC-DC converters which apply different voltages to the controller input than to the outputs. You can track the module voltages independently from the battery voltage. This means greater flexibility becomes inherent in the range of the input voltage.

These types of controllers can charge a 12v battery from the different modules found in the solar cells. You can also apply MPPT algorithms to the controllers which drive the solar module to produce the maximum power available.

Serial Controllers: These controllers will disconnect the battery from the solar module to help regulate the system. Basically, if the circuit is open, the module is directed towards the open circuit mode and the current in the module is reduced to nothing. Inside the serial controllers are two anti-serial MofFets that will prevent the current from flowing in both directions.

Other Items to Consider

With shunt and serial controllers along with MPP trackers, each of them has its advantages in PV battery systems.

Shunt controllers are excellent for all solar power systems because they create the best charging efficiency which is the crucial issue for all PV battery systems. In addition, they provide excellent telecom applications because of their EMC performance as well. If the battery is charged from a fixed voltage source, then a serial controller is arguably your best selection.

However, in regions that have low temperature and irradiation, an MPP tracker can provide more energy to the batteries than other types of controllers. This is also true if the number of cells found within a solar module doesn’t fit the battery voltage or if thin-film modules are used, then an MPP tracker is the right choice.

Taking all of this information into account can seem enormous at first, but the more research you do, the easier it will be to have this knowledge at hand. In fact, everyone who has a solar power system in their home should learn what they can about how their system works, what the technical requirements are and how they can add to the system to improve the overall efficiency.

Armed with this knowledge, you can now find the right solar charge controller for your solar panel unit. Remember to seek out expert advice, take into account the size of the system and use all the details known to find the right type of controller.

For those who want to go off grid with their solar power systems, having a solar charge controller is the crucial part in getting the most out of your battery pack. So be sure to take in all the information possible so you can get the right solar charge controller.

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