You’ve probably heard over and over that, a typical off-grid solar system has a solar panel, charge controller, battery, and an optional inverter.
You might be wondering then if the battery is a must-have and if depending on your application, you could wire your appliances directly across the charge controller (without a battery connected).
This post explains whether you can use a solar system consisting of a solar panel and charge controller without a battery, whether it will likely work or not, and the options available to you if you choose not to use a battery.
Is a Battery Necessary?
Unfortunately, the battery is usually required. It supplies the charge controller with the necessary power for its internal electronics.
In some applications, you could do away with the charge controller (and battery) and connect the appliance directly to the solar panel.
You’ll need to double-check though that the solar panel and appliance DC voltages match and the appliance can handle the output current from the solar panel.
Do not for example connected a solar panel with an output voltage of 18V to an LED bulb that requires 12V or the bulb will burn out.
Additionally, some sensitive appliances like laptops require stable output power and do not tolerate fluctuations in power supply.
What Are the Limitations of Connecting an Appliance Directly to a Solar Panel?
While connecting an appliance directly to a solar panel may be viable in some applications, there are some associated dangers:
#1. There is a danger that the current output can exceed what the appliance can handle and damage it.
#2. The appliance’s performance will not be consistent and will depend on sunlight falling on the solar panels. In the case of the fan, its speed depends on how much sunlight and correspondingly the solar panel generates.
#3. The appliance can only work when the sun is available. When the sun goes down at dusk, there’ll be no power (no battery storage available) and the appliance will stop working.
Examples of Appliances that you may be able to Connect Directly to a Solar Panel
Fan, Heater, LEDs, and Cameras, water pumps are some examples.
Make sure that the current and voltage output of the solar panel does not exceed what the appliance can handle.
Can you use an MPPT controller without a battery?
Probably not, most charge controllers need to be connected to a battery with a minimum voltage to activate their internal electronics and start work as designed.
You’ll likely need a battery with a minimum voltage for the charge controller to work. Most charge controllers are designed this way.
In some situations, you may be able to connect the appliance directly to the solar panel.
Make sure that the output voltage matches what the appliance requires and that it can handle the solar panel’s output current.