Solar Charge Controller Basics: What Is a Solar Charge Controller?

80% of the energy used globally still comes from fossil fuels, which are the main driver of climate change. But by 2030, there are around 660 million people will still be without access to electricity, and nearly 2 billion people will still rely on polluting fuels and technologies for their daily lives. By combining more renewable energy projects with energy storage, we can increase investment and use of clean energy and gradually reduce the use of fossil fuels to reduce environmental pollution. Among existing renewable resources, investing in solar energy is a wise choice. Having a better MPPT solar charge controller to improve the efficiency of solar energy storage and use can maximize the benefits you expect from using solar energy resources.

Ⅰ. What is a solar charge controller?

Solar charge controllers are used to prevent overcharging of batteries by regulating the voltage and current from the solar panels to the battery. They can also protect devices connected to the battery in off-grid systems. Most of the time using a controller in an off-grid system can extend battery life.

Ⅱ. Types of solar controllers

There are two main types of solar charge controllers on the market:

PWM Controller: A PWM controller regulates the voltage from the solar panel to the battery at a fixed rate. They are ideal for smaller, simpler solar systems, low cost and low maintenance and are an older, less efficient type of solar charge controller.

MPPT Controller: MPPT controllers are efficient and versatile, making them more suitable for larger and more complex solar systems. They can track the maximum power point of a solar panel, deliver up to 30% more power than PWM controllers, and can be used with any type of solar panel configuration. It’s ideal for those who want to make the most of sunlight, want to save more energy, and those who want to protect their batteries from being exposed to too much sunlight for a long time. Also beneficial for domestic, industrial, and commercial purposes.

PWM VS MPPT Solar Charge Controller Details Comparison:

Off-Grid (12V) Grid-Tie (Variable Voltage) 
Variable 170W or larger
 Warm or Hot Any
$15-$125 $28-$324

Ⅲ. The Working principle of solar controller

The charge controller regulates the amperage and voltage that is delivered to the loads and any excess power is delivered to the battery system so the batteries maintain their state of charge without getting overcharged.

It is recommended that you connect and disconnect in the following order when installing a solar charge controller: 1. Connect the battery to the controller 2. Photovoltaic system connected to controller 3. The controller is connected to the electrical load

You can reverse the order when disconnecting, The battery provides power to the controller, so you will always make sure that the solar panel and electrical load are disconnected before connecting or disconnecting the battery from the controller. Connections between the battery, load, PV and controller should have disconnect switches to enhance safety and ease installation and troubleshooting.

Ⅳ. Five Factors that you have to consider when purchasing a solar controller

Battery Compatibility: Is the controller compatible with the type of battery you have? If it is not compatible with your battery type. The controller will not work, so be sure to pay attention to compatibility when purchasing. LiFePO4 Battery will be a good choice.

Solar panel type: Most off-grid solar panels are 36-cell panels designed for 12 volt battery charging current and rated for typically around 30 amps. These systems work well with PWM controllers and lithium batteries. 60-cell and 72-cell panels are typically used with grid-tied solar panel systems and are of higher voltage (24 volt systems or higher), thus requiring an MPPT solar controller.

System Capacity: Choose a solar controller that matches the specifications of your system. For example,  RV (Recreational Vehicle) solar charge controllers are essential components of solar power systems for RVs. The capacity of the off-grid system you are using needs to match the voltage of the home battery and you will be able to charge properly. MPPT is suitable for any system size and also improves the conversion efficiency of solar energy, so using MPPT saves you time charging, and usually the PWM doesn’t match up in large systems.

RV Solar Charge Controller Operating Ambient Temperature: the MPPT controller works better than the PWM controller when the weather gets cold, the MPPT controller can capture the excess voltage as the temperature drops and the voltage rises, In warm climates where temperatures are typically not very low, there is no additional voltage and no need for an MPPT controller. A temperature sensor is another additional feature that can be added.

Price: Paying extra just to get more power is an unwise decision and it has the potential to cost you a lot of money. Having the most suitable cheap MPPT charge controller is quite important for your solar power most of the time. There are recommendations listed below for you.

Ⅴ. Solar controller recommendation-Bateria Power 20A MPPT Solar Charger Controller With Bluetooth

You might have a proper selection after learning the information of the solar controller above. If you are still confused and can’t decide which solar controller is the best choice. Bateria Power 20A MPPT Solar Charger Controller with Bluetooth might be a good choice for most beginners or those who don’t have enough budget.

Here are some basic specifications of the Beteria power solar charger controller.

Noload Loss: 12V/20mA:24V/20mA

System Voltage: 12V/24V AUTO

Max Solar Input Voltage: 12V/30Voc;24V/60Voc

Rated Solar Charge Current: 20A

Max Solar Input Power: 300W/12V:600W/24V

Operating Temperature: -20°C~+45°C

IP Protection: IP45

Net Weight: 350g

Operating Altitude: ≤3000 meters

Controller Dimension(mm): 150*79.3*35

It can be seen from the parameters that it is suitable for 24V and 12V systems and can meet most daily needs. If you are an outdoor activity enthusiast, this kind of controller is easy to carry and can reduce the load when going out. It is also easy to install and can build an outdoor off-grid system anytime and anywhere.

The most important thing is that it can be controlled by Bluetooth and monitor your charging in real-time, which can reduce your exposure to the scorching sun. 100% Efficiently MPPT Charging efficiency is up to 30% more efficient than PWM charging. It not only maximizes the efficiency of solar energy conversion Efficiency also saves you time.

If you are on the fence about purchasing a solar controller, the Bateria Power MPPT solar charge controller might be a choice. The 20 amp solar charge controller is enough for off-grid homes and small homes with modest power needs. Here you can check more details:

Ⅵ. Solar Charge Controllers Frequently Asked Questions 

Q: Do solar panel systems require a charge controller?

A: Not all solar panel systems require a charge controller, but they are a must for any off-grid solar plus storage system. They provide the basic function of preventing the battery from overcharging and discharging when the panel is not in use. If your solar system is connected to the grid, a charge controller is not required as any excess power is diverted from the battery system and directed back to the grid.

Q: How big of a solar charge controller do I need?

A: Multiply the number of panels and the wattage per panel to get the total wattage (more likely kilowatts) of the solar array. Then, divide that number by the voltage of the battery pack to get the amperage. Finally, if you live in a cold climate, add 25%. For example, if you have a 500W solar array, the next thing you need to consider is the battery voltage, such as 24V. You can divide the wattage of the solar array by the battery voltage to get 20.83 amps. But you still need to increase the current increment by about 25% so that you get 26.03 amps. We can then round this up to make it easier to choose the correct MPPT. Therefore, you need a 24V, 26MPPT charge controller. Calculate the voltage and current you need and you will get the correct MPPT that will best fit the solar setup you already have.

Q: How to maintain and clean it?

1. Do not allow the MPPT controller to be immersed in water for a long time.

2. Improper use and installation will reduce the service life of the product.

3. Regularly remove dust from the MPPT charge controller. 

Q: Where should solar panels be placed in relation to batteries?

A: It is required to use thick wires If your solar panel is far away from the battery, otherwise the power loss and voltage drop will be reduced. Sometimes it is stressful that there is no budget and space to use thick wires. So choosing a good MPPT controller can help us maximize charging efficiency.

Q: What is a load or “low voltage disconnect” output?

A: Some controllers also have a “LOAD” or LVD output that can be used with smaller loads, such as small appliances and lights. The advantage is that the load terminals have a low voltage disconnect, so it will shut down any device connected to the load terminals and prevent excessive drain on the battery. Load outputs are typically used for small non-critical loads such as lights. There are some, like the Schneider Electric C12, that can also be used as lighting controllers to turn on the lights when it’s dark, but the Morningstar SLC lighting controller is usually a better choice. Do not use the load output to run any inverter except very small inverters. The inverter can have a very high inrush current and can burn out the controller.

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