The load output is a feature available in new charge controllers, mostly MPPT that allows you to regulate, monitor, and maximize the current reaching certain appliances either manually or automatically using algorithms.
Most charge controller manufacturers assume there is no need to monitor the charging process of smaller PV systems. For example, you will rarely find features in controllers that check the voltage output of led bulbs or when charging phones.
This is wrong as this system use power and can be affected by excess current. To curb these issues, some MPPT charge controllers have included a feature known as load output. This feature allows loads to be switched off and on depending on the charge available in the solar battery.
There are two common methods that you can use to switch the load output on and off.
- Use of relays
When choosing relays for your load output, consider the size of the load.
Standard relays that can operate with a substantial load need a coil that keeps the contact closed against the tension of the spring. They also prevent contact arcing. With these relays, you need some electrical energy to close and keep the contact closed.
You can also use latching relays that use the energy of the coil to keep the contact closed. Latching relays are however expensive and a bit larger.
- Using a transistor
Metal Oxide Semiconductor Field Effect Transistor (MOSFETs) are very small devices that can switch the load output very fast. They do not suffer from arcing problems and also a use very less amount of energy to close and keep the contact closed for long.
Switching the load output very fast can cause some disadvantages to the whole system and the device itself.
Is the Output of the Controller AC or DC?
Charge controllers receive current directly from the solar panel. This means they operate in DC form. However, to power most appliances at home, the current needs to be converted into AC form. An inverter is used in that case.
Modern charge controllers for the smaller system have a feature known as DC load output. This device is ideal for ensuring DC appliances such as street lighting are charged efficiently and protected from surges.
Charge controllers for larger systems on the other hand do not have the DC-coupled loud output. They use the common features provided directly.
Do charge controllers Load Output Terminals Always Have Power?
Provided the charge controller is connected to a solar battery and both devices are in the right condition, then the load output terminal has power.
On an occasion where the solar battery’s voltage is lower than that of the charge controller, the load controller automatically disconnects the load.
Some charge controllers come with a manual switch. If the switch is turned off then the charge controller load output terminals will not have any power.
Why Solar Charge Controller Load Output Terminals May Have No Power?
There are three occasions where your solar charge controller load out terminals may have no power;
- If the solar battery and the charge controller are defective.
- The solar battery voltage is below the voltage of the charge controller.
- Check the manual switch available is switched off.
So if your solar charge controller load terminals are not registering any power, check the three perspectives.
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”.
