Will A Solar Controller Function In The Absence Of Batteries?

As solar power becomes more popular, people are starting to ask questions about the various components of a solar power system. One of the most common questions is will a solar controller function in the absence of batteries?

In this article, we will explore this question and provide a detailed explanation of how solar controllers work and whether they need batteries to function.

What Is A Solar Controller?

A solar controller, also known as a charge controller or regulator, is a device that regulates the amount of power that flows between a solar panel and a battery. The purpose of a solar controller is to prevent the battery from being overcharged or undercharged, which can damage the battery and reduce its lifespan.

Solar controllers are essential components of a solar power system and are necessary for maximizing the efficiency and lifespan of the system.

How Does A Solar Controller Work?

A solar controller works by monitoring the voltage of the battery and the voltage of the solar panel. When the voltage of the battery drops below a certain level, the solar controller will allow the solar panel to charge the battery.

When the battery is fully charged, the solar controller will stop the charging process to prevent overcharging.

Solar controllers use a process called pulse width modulation (PWM) to control the flow of power between the solar panel and the battery. PWM is a technique that involves rapidly turning the power on and off to regulate the voltage and current flow.

This allows the solar controller to maintain a steady flow of power to the battery without overcharging or undercharging it.


Do Solar Controllers Need Batteries To Function?

The short answer is no, solar controllers do not need batteries to function. Solar controllers can be used to regulate the flow of power between a solar panel and any load, not just a battery. For example, a solar controller can be used to regulate the flow of power between a solar panel and an inverter that is connected to the grid.

However, in most solar power systems, batteries are used to store excess energy generated by the solar panel. This stored energy can be used when the solar panel is not generating enough power, such as at night or during cloudy weather.

In these systems, a solar controller is essential for preventing the battery from being overcharged or undercharged.

If a solar power system is designed without batteries, a solar controller can still be used to regulate the flow of power between the solar panel and the load. However, in this case, the solar controller would not be necessary for preventing overcharging or undercharging of a battery since there is no battery present.

Types Of Solar Controller

Charge controllers are a critical component in solar energy systems, ensuring that batteries receive the right amount of energy to stay charged while avoiding overcharging. The two primary categories of charge controllers are : pulse-width modulation (PWM) and maximum power point tracking (MPPT).

Pulse-Width Modulation (PWM)

PWM is the simplest and most cost-effective method of controlling power flow between solar panels and batteries. PWM charge controllers can be found on the market for around $17 to $40. A PWM charge controller prevents the battery from overcharging by switching power flow on and off several hundred times per second, which reduces the average voltage coming from the solar panels. This process produces “pulses” of power, and the width of the pulses reduces the average output voltage.

A charge controller, for instance, might change the pulses so they are on 82% of the time and off 18% of the time if it is receiving 18 volts from a solar panel. This would reduce the average voltage by 18%, down to about 14.8 volts, which can be used to charge a partially depleted AGM battery.

As the battery gets closer to full charge, a PWM charge controller shortens the pulses even further, down to around 77% of the time, or 13.8 volts, to prevent overcharging.

The downside of PWM is that excess energy generated by the solar panels is wasted to reduce the output voltage. This means that the output voltage of the solar panels must not be significantly higher than the voltage of the battery bank with a PWM charge controller, to minimize the energy wasted.

The PWM charge controller will reduce a solar array’s output voltage if it is far higher than the battery can handle, squandering the excess.

For small off-grid applications, like a few solar panels connected to a couple of batteries, an 80% efficiency rating is sufficient, especially considering the low cost of a PWM charge controller. However, for larger systems with higher output, it is generally preferable to use MPPT charge controllers.

Maximum Power Point Tracking (MPPT)

MPPT charge controllers operate by converting incoming power from solar panels to match the theoretical highest-efficiency output at the correct input voltage for the battery.

The solar panel output is converted to the maximum current that can flow at a voltage that the battery can take by the charge controller.

The main advantages of MPPT charge controllers are greater efficiency and compatibility with higher voltage solar arrays. This means that a 12V battery bank can be charged with a larger solar array wired in series, as long as it remains within the controller’s amperage rating. This limit can be calculated by dividing the total wattage of the solar array by the voltage of the battery bank to obtain the maximum possible output in amps.

Using the same example as before, if a solar panel is putting out 100 watts, or around 5.5 amps into 18 volts, an MPPT charge controller would convert the output to 14.8 volts but lose about 5% of the power in the process. So the MPPT controller’s output current would be around 6.4 amps, times 14.8 volts, or 95 watts.

Advantages Of Using A Solar Controller

Using a solar controller in a solar power system offers several advantages. These include:

Protection Of Batteries:

Solar controllers are essential for preventing the overcharging and undercharging of batteries. This protection ensures that the batteries last longer and perform better, which can save money in the long run.

Improved Efficiency:

Solar controllers use PWM to regulate the flow of power between the solar panel and the battery. This technique maximizes the efficiency of the system and ensures that the battery is charged quickly and efficiently.


Solar controllers can be used to regulate the flow of power between a solar panel and any load, not just a battery. This makes them highly flexible and adaptable to a wide range of solar power applications.

Common Charge Controller Features And Settings

Charge controllers come with a variety of features and settings, depending on their complexity. Even the most basic PWM charge controller typically allows for the selection of battery type and voltage for the battery bank. Additionally, the controller may have indicator lights to show the current charging phase, including bulk, absorption, and float.

More advanced PWM and MPPT models come equipped with a small LCD display for programming and data display, as well as a heat sensor port to monitor battery temperature. These controllers may also have a communications port to connect to an external display or computer, allowing for further data analysis.

For those seeking even more advanced features, some charge controllers offer Bluetooth connectivity and an app for customizing settings. With these additional options, users can monitor and control their solar power systems from their mobile devices, making it easier than ever to manage their energy production and consumption.

Looking for a charge controller for your solar setup? There are several options on the market for you. Whether you visit a solar supply store or browse an online marketplace like Amazon, you’re likely to find a wide range of choices.

Few Suggested Products

If you’re looking for an affordable option, you can get a PWM charge controller for as little as $15. While they may lack some features, these controllers are still quite reliable for their price point. For better quality PWM charge controllers, you can expect to pay under $50. Meanwhile, full-featured MPPT charge controllers range in price from $100 to $500.

To help you navigate the many options available, we’ve put together a list of recommended charge controllers for a medium-sized off-grid setup. These options vary in price, so you can choose the one that best fits your needs and budget.


The Victron Energy SmartSolar MPPT 100V 50 amp 12/24-Volt Solar Charge Controller is a top-quality controller that maximizes energy output through MPPT technology. Its Bluetooth connectivity allows easy monitoring and configuration via smartphone or tablet. It is built to last with high-quality materials and built-in protection features. A great investment for off-grid solar systems.

Renogy Wanderer Li 30A 12V

The Renogy Wanderer Li 30A 12V PWM Negative Ground Solar Charge Controller is a versatile and reliable option for off-grid solar systems. Its temperature sensor function helps regulate charging to extend battery lifespan. The negative ground design and built-in overcharge protection make it easy to install and protect your battery. A great choice for those looking for an affordable yet effective charge controller.

EPEVER Tracer BN 30A 12V/24V MPPT



The EPEVER 30A MPPT Solar Charge Controller Tracer BN Series is a high-performance option for off-grid solar systems. Its MPPT technology maximizes energy output and it can identify system voltage automatically. With a negative ground design and built-in protection features, it is easy to install and keeps your system safe. A great investment for anyone looking to get the most out of their solar panels.

In conclusion, solar controllers are essential components of a solar power system that regulate the flow of power between the solar panel and the battery. While solar controllers do not need batteries to function, they are necessary for preventing the overcharging and undercharging of batteries in most solar power systems.

Solar controllers offer several advantages, including protection of batteries, improved efficiency, and flexibility. If you are planning to install a solar power system, be sure to include a solar controller in your design to ensure maximum efficiency and longevity of your system.

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