What Is The Short Circuit Current Of A Solar Panel? What Happens!

Solar panels come with certain specifications that influence the design of the solar system. One of them is the short circuit current. Short circuit current is a measure of how much current a solar panel produces without a load on it.

But how do you work out the short circuit current and why is it even important? Today we will look at what some of the specifications on a solar panel mean and why you should pay special attention to them.

Knowing how to read the values on the spec sheet of a solar panel is critical to designing a more efficient solar system. It can also help prevent unnecessary and expensive damage to your equipment. If you want to take one step closer to designing better solar systems then keep reading.

What Is Short Circuit Current And Open Circuit Voltage In Solar Cell?

A short circuit current is the maximum current of a solar panel without a load connected. The open circuit voltage is the maximum voltage of a solar panel without a load connected to it. They are measures of the maximum current and voltage a solar panel can produce.

A solar panel produces both current and voltage. To get a better picture of why these specifications are important let’s dig a little deeper into what they are.

Short circuit current

All solar panels come with a short circuit current rating. This is when the current in the solar panel is at its maximum and there is no voltage. In this case, there is no power coming from the solar panel because there is no voltage. To get power from a solar cell you need both current and voltage.

Current (Amps) x Voltage (Volts) = Power (Watts)

Short circuit current is important because it’s used to calculate the size of the conductors or wires you will use in your system. The short circuit current is also used to determine the size of the other components in the solar system such as the breakers for example.

The short circuit current is always given by the manufacturer on the back of the panel as the Isc and is expressed in amps (A).

Open circuit voltage

Open circuit voltage is a measure of the voltage when there is no current. It is the maximum voltage the solar panel can produce. The open circuit voltage is important because it is what you will use to calculate the maximum voltage you can use with the other components in your solar system like your charge controller or inverter.

The open circuit voltage ranges from 21 to 42V depending on the nominal voltage of the solar panel. Open circuit voltage is also given by the solar panel manufacturer as the Voc and is expressed in volts (V). Source

The solar panel Voc is measured using a multimeter.  Here is how you find it:

1. Set the multimeter to read volts.
2. Angle the solar panel towards the sun.
3. Connect the positive lead of the solar panel to the negative lead.
4. Clamp the multimeter around the wires to get the reading.

In most cases, the reading will not exactly match the one given by the manufacturer. It should however be within 10% of the rating supplied on the datasheet.

Now you know what the short circuit current and the open voltage in a solar panel are. But how do you find the short circuit current?

On a side note, check out our post on “Which Solar Panel Connector Is Positive? (Types Listed) “

How Do You Find The Short Circuit Current Of A Solar Cell?

Short circuit current is given as the value Isc on the datasheet of a solar panel. Short circuit current can also be measured using a multimeter.

To find the short circuit current of your solar panel here are the simple steps you need to follow:

1. Connect the positive lead or terminal of the solar panel to its negative lead. This is called shorting.
2. Set the solar panel out in the sun.
3. Switch the multimeter to measure amps.
4. Clamp the multimeter around the connection created between the positive and negative terminals.
5. The value given by the multimeter is the short circuit current.

Shorting and testing of the Voc of a solar panel is typically done before installation. The values you obtain will differ slightly from the values printed on the datasheet of the solar panel. This is normal and why you test in the first place. To give you the real data you will use to design your system.

The data given by the manufacturer are values under standard test conditions in a lab. They do not reflect the real-world conditions the solar panel is exposed to so they are not reliable enough to base a solar system design on. The short circuit current should be within 20% of the value given by the manufacturer.

What Happens If You Short Circuit A Solar Panel?

A short circuit in a solar panel can occur by accident or deliberately. The deliberate shorting of a solar panel is to determine the short circuit current of a solar panel or simply if it is working. This is a standard procedure of solar system design and it does not affect the solar panel.

Also, check out “How Long Before Solar Panels Start Working? (How to Check if It’s Working!)“

Generally, when a short happens by accident it is caused by shading or equipment failure. The latter can be the result of a worn-out cable or using the wrong size cable for example. When a short circuit occurs, a path is created that detours the current from its correct path.

If part of a solar panel falls into shade this will cause the solar cells in the panel to heat up. The power output of the solar panel will drop as a result. If the temperature continues to rise this can damage the solar panel. In more extreme cases the increased heat can lead to a fire.

Source

For more on this, we highly recommend that you check out our post Can You Short Out A Solar Panel? What Happens If You Do & How To Deal With It !

What Is Short Circuit Current In Inverter?

Inverters have a maximum current input they will accept from an array of solar panels. They also have a current output which is the current they produce that gets distributed to an appliance. The short circuit current is a value taken from the short circuit of the solar panels as they produce current.