In most cases, a solar charge controller cannot be used without a battery. This is because the charge controller’s primary function is to regulate the voltage and current from the solar panels to protect the batteries from overcharging or over-discharging. Without a battery, the charge controller has no way to dissipate the energy generated by the solar panels, which can damage the controller itself or the solar panels.
However, there are a few special cases where a solar charge controller can be used without a battery. These include:
- Using a dump load: A dump load is a resistor that is connected to the charge controller to dissipate excess energy. This is typically used in systems where the solar panels are producing more energy than the load can use.
- Using a DC-DC converter: A DC-DC converter can be used to step down the voltage from the solar panels to a lower voltage that can be used by a DC load. This is typically used for small loads, such as USB devices.
- Using a grid-tied inverter: A grid-tied inverter can be used to convert the DC output of the solar panels to AC electricity that can be fed into the utility grid. This is typically used in systems where the solar panels are generating more energy than the load can use.
In general, it is not recommended to use a solar charge controller without a battery unless you are familiar with the risks and have a specific application that requires it.
To find out the main reason why your solar PV system must have a charge controller, keep reading this guide.
What is the operation of a solar charge controller?
Solar batteries or what is termed as deep cycle batteries have usually operate by constantly discharging and recharging. Sometimes the solar panel sends high current to a solar battery. If this charge exceeds the rated voltage, the battery might get damaged.
To prevent that from happening, a charge controller should be installed into your solar PV system.
A charge controller also known as regulator main purpose is to regulate the amount of current being passed to the battery. Since a solar battery has many discharge and recharge cycle, if the large amount of current reach the same battery in a long time, the battery loses its efficiency.
These devices detect the amount of voltage needed by a battery to fully charge, and allows the same amount to be passed. When the solar battery is almost fully charged, the regulator stops anymore current from reaching the battery. The battery then charges to capacity using a technique known as float charging.
Sometimes like during the winter, solar energy is unreliable. If the voltage output in a home is higher than the current input, the solar battery might get over discharged. A solar battery attached to a charge controller will retain some amount of charge for a long period.
Therefore if you want to use the solar battery efficiently, pair it with a high-quality charge controller.
Eng. Matthew Joseph Nandirio is the Founder of walkingsolar.
After graduating from the University of Houston in 2002, matt started working as a Solar Electrical Engineer for several multi-national solar energy companies.
He has a wide range of experiences including solar system requirement analysis, planning, maintaining, debugging and even solar device development through research.
He now shares his 20 years of expertise through his articles on the walkingsolar website.
Further, he is also the author of two books on Solar Technology, “Solar Power for Villages” and “DIY Solar System for Dummies”.