As a solar PV system owner, it would be advisable to install a charge controller. A charge controller ensures solar energy is fully maximized. Among the best charge controllers available for solar is the MPPT.
MPPT, which is Maximum Power Point Tracking, is a powerful device that can significantly change your solar energy usage experience. This device is connected to the solar battery, the inverter, and the solar panel. But can you connect MPPT to the inverter without a solar battery?
It is possible to connect the MPPT charge controller to the solar system without a solar battery. However, for efficiency, ensure you have a solar battery that can accommodate the charge controller.
Using a charge controller without an as-lar battery can also damage the charge controller because a solar battery acts as a medium for connecting the inverter to the charge controller. In case the charge controller gets damaged, you might lose your warranty.
What does an MPPT controller do?
An MPPT charge controller balances the voltage and the current between the solar battery and the solar panel. It does so by detecting the voltage on the solar battery and sending an array of current from the solar panel to replace any used charge.
For example, suppose the sun is hot, and the solar panel harvests maximum sunlight energy. In that case, the charge controller will detect the surplus, maximize the charging and stop any more current from reaching the solar battery when the battery is full.
Again if there is no sunlight energy being harvested by the solar panel, MPPT will reduce the amount of charge leaving the solar battery. This ensures the solar battery is not over drained or overcharged.
One advantage of using an MPPT charge controller over PWM is that MPPT allows the solar panel to send more energy to the battery when it is drained. On the other hand, PWM ensures the voltage and the currents are balanced.
Can I use MPPT without a battery?
You can use an MPPT charge controller without a solar battery if the load being powered is not that big. However, this is a bad idea and does not work all the time.
If you are using solar energy to power appliances like refrigerators, washers, and light bulbs, you will need a steady energy supply. This might not be possible if you use a charge controller without a solar battery.
A charge controller cannot hold power backup when need arise. It acts as a device that maximizes the solar battery charging process.
Using a charge controller without a solar battery cannot work at night. The charge controller sends the power to an inverter directly from the solar panel. The solar panel only detects sunlight energy during the day.
A charge controller can also get damaged if it is overpowered and the excess charge has nowhere to be stored. You might end up getting denied your warranty if the manufacturers know.
You should invest in a powerful solar battery to prevent this from happening.
What MPPT controller do I need?
For you to enjoy the advantages of MPPT controllers, you need to size the charge controller properly.
MPPT charge controllers are rates into three different categories.
The first rating is according to the amount of voltage a solar battery will work with. This means MPPT should accommodate whatever amount of voltage a solar battery needs.
The second rating considers a voltage window provided to ensure the charge controller does not get damaged and works efficiently. For example, if a solar 12V solar battery a voltage window of between 18V and 150V is provided.
If the voltage sent from the solar panel exceeds the voltage window maximum, the charge controller can be permanently damaged. On the other hand, if the voltage sent is below 18V, the charge controller will not detect any voltage.
When rating the MPPT charge controller according to voltage input, weather conditions like cold are considered. Standard solar panels, made of silicon, have a voltage rating of 25°C. This rating is in Standard Test Conditions (STC).
The third rating of the MPPT charge controller is in the form of output current. This is done by dividing the wattage of the solar array by the voltage of the solar battery. The answer you get will be the output current of MPPT.
When sizing the charge controller with the output current, you should consider the peak amount. In a way, a surplus of the solar array will not damage the charge controller.
If the rating you find is lower than your solar panel can produce, you need to add another charge controller. Otherwise, the charge controller will be damaged permanently.
Ensure you use the correct number of solar panels and charge controllers to prevent disruptions.
Are MPPT controllers worth it?
If you have a solar PV system at home, it would be advisable to connect a charge controller to your solar panel.
An MPPT charge controller, in particular, ensures your solar battery is efficiently charged while preventing over-draining.
It reduces the chances of the solar battery getting defective faster while ensuring you enjoy the free solar energy for long, even during the day. Therefore MPPT charge controllers are worth it.
Although you can use an MPPT charge controller without a solar battery, it is advisable to have a battery just in case.
A charge controller cannot hold backup power for when the need arises. It, therefore, may not be helpful at night if there is no solar battery backup.
MPPT charge controller ensures the solar battery is charged efficiently, and any surplus of solar energy is prevented from reaching the solar battery if the sun is hot. It also contains the excess energy from being drawn out of the battery when there is no sunlight.
Although connecting this device is very easy, sizing affects how well the charge controller works. You should consider;
- The voltage required to power a solar battery.
- Cold weather and input voltage.
- Warm weather and voltage output.
Ensure you match the size of your solar battery with that charge controller. If the voltage being sent from the solar panel is higher than the voltage window provided during the MPPT rating, you should add another charge controller. Otherwise, the controller can be permanently damaged.
Eng. Matthew Joseph Nandirio is the Founder of walkingsolar.
After graduating from the University of Houston in 2002, matt started working as an electrical and electronic 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”.