How to reduce solar panel VOC (Important!)

The VOC is the Open Circuit Voltage – is your solar panel or a solar array is producing too many volts? If so, there is a simple way to reduce the number of volts that a solar panel sends down the circuit.

But, first, let’s discuss why a solar array may produce too many volts. 

It is the job of the array to produce as much energy as possible. However, there are situations where the array will produce too many volts.

Primarily that is a situation when you have too many solar panels connected to a low voltage controller or other devices. 

In this blog, we discuss:

  • What VOC is to solar energy
  • What Solar Controllers Do
  • The information you need to collect to use a VOC calculater
  • Options for reducing solar output

Solar controllers are rated by the maximum number of volts they can handle. The danger of sending too much voltage to a controller is an electrical fire and damage to other solar components, especially solar batteries. 

Voltage Meter Checking Ac Volts White Background
Voltage Meter Checking Ac Volts White Background

What is VOC in a solar cell?

What is VOC? VOC is the maximum voltage of an open circuit produced by a solar panel. Open Circuit Voltage (VOC) and is a product of the forward biases of the solar cell. 

You cannot go by the volts rating on the solar panel box because a 12v solar panel will produce as much as 18v-22v. However, you can use a voltmeter to test the actual voltage.

How many volts the solar panel gives off reflects how many cells the solar panel has and the rating for voltage per cell. 

How can you reduce the voltage of a solar panel?

The first thing to do is double-check your calculations before you buy solar panels and your solar regulator. Your goal is to keep the voltage from the panels at 2/3s of the average maxim voltage of the controller.

For example, if the controller is rated at 150 volts, you want to keep the average solar output to the controller around 100 volts.

Doing so takes into account the varying amount of energy a solar panel produces throughout a day. For example, in the morning, the energy will be lower than it is at noon. 

Keep The String Short

The second part is fully controllable. Most of the trouble from overloading a solar controller occurs when you string too many solar panels together.

For example, if your solar controller has a maximum voltage of 150 volts, and each of your solar panels produces 36 volts, and you string five panels into a string, you get 180 volts.

The answer is to string fewer panels; in this example, strings of three panels are ideal. If you need to string five 36volt panels together, you need a controller with a maximum voltage rating in the 270-volt range. 

The answer is to adjust the number of panels or to increase the capacity of the solar controller. There are other possible answers, such as creating circuits that reduce energy is just wasting potential energy.

You’ve paid for the panels; use as much of the energy as possible. Doing so raises the ROI of the investment you’ve made in the panels. 

Other Options

If you are grid-tied, other options would be to allow the excess energy to flow to the utility grid. That is not a bad solution if your local utility provides you with solar credits. If they don’t, you are giving away energy for free.

There is the small benefit of providing clean energy where other consumers might still use dirty energy. 

What happens if you are off-grid? If your solar array is producing too much energy, you have two choices. Reduce the number of panels or find a way to use more energy.

Off-grid systems have battery backup, and if there is too much energy passing through the control, those batteries will die prematurely.

You can install fuses and breakers before the solar controller, but you must constantly monitor the array. 

What is VOC in solar charge controllers?

A VOC solar charge controller is a device that limits the amount of energy that passes through it. We often see these in solar array systems where a solar battery storage system is in place.

They are sometimes called step-down controllers or Bucks Controllers. Other types of solar controllers include PWM and MPPT.

All of these work to regulate the amount of voltage coming from the array. Each is available in different ratings for maximum voltage. 

The other solar panels’ other job is to stop the battery storage system from reverse feeding energy back into the panel.

So when the sun goes down, and the chemical reaction within the panels stops, the energy from the batteries or the grid, if you are grid-tied, can flow backward into the solar array. The solar controller prevents that from happening. 

Solar Controller Sizing 

Solar controllers come in a range of sizes, and you match them to the output of your solar array. As described above, a good rule of thumb is to choose a solar controller that can handle more energy than your array can produce.

That tip helps compensate for the fact that the amount of energy a solar panel creates is not static; It is dynamic and will ebb and wane throughout the day. 

How do you calculate the Voc of a solar panel?

Calculating the VOC of solar panels is complicated. Thankfully, there is a VOC Calculator

What you will need to know is:

  1. The Solar Panel Open Circuit Voltage (VOC)
  2. Solar Panel Maximum Power Point Voltage (Vmp)
  3. Solar Panel Temperature Coefficient of Pmpp
  4. Solar Panel Temperature Coefficient of VOC. 

If your eyes are rolling back in your head, you can relax. All of this information is on the solar panel data sheet that is attached to your solar panel. Chances are you can also find all of this information online at the manufacture’s website.

Additional Data Needed 

5. is the maximum temperature for the site, in Celsius. 

6. What is the minimum temperature for the site in Celsius. 

7. How many Solar Panels are in a string. 

Once you plug in all of this data, the calculator will do the rest for you. 


General Solar Panel FAQ

What Problems Do Solar Panels Solve?

In environmental terms, solar panels can potentially solve a handful of problems, including;
1. Air pollution
2. Water pollution
3. Greenhouse gases
4. Reduction in fossil fuel use

For individuals, solar energy allows you to become completely self-sufficient when it comes to your electricity needs and can save you a lot of money in the long run.

What Are 3 Important Uses Of Solar Panels?

The three most important uses of solar panels are;
1. Solar electricity. This can be used to power almost any appliance in your home, including TVs, computers, and fridges.
2. Lighting. In addition to the use of low-power, LED lightbulbs, solar panels can provide an efficient, low-cost, and environmentally friendly way to provide lighting to homes. 
3. Portable solar. In our modern, always-connected lives, our phones, tablets, and computers are almost always with us, and all run on batteries. Portable PV chargers can help keep our batteries topped up no matter where we are, as long as there is some sun to charge them.

Do solar panels give you free electricity?

Once the cost of the array is paid in full, the energy it produces is free. There are ongoing maintenance costs, too, such as annual panel cleaning, etc. 

How much will my electric bill be with solar panels?

Suppose your solar array includes a solar battery backup system, and it is large enough to fully cover your energy usage per day. In that case, your monthly electric bill will be next to zero dollars, even with a grid-tied system. 

If your solar array does not include a solar battery backup system, then at night, your house or business will use grid electricity. That cost will vary but expect to pay from 1/3-2/3 of your average electric bill, and that cost will fluctuate seasonally. 

Do you save money with solar panels?

The simple answer is, Yes, you save money with solar panels. There is an initial upfront cost, but since solar panels are warrantied for 25 years, you will save money over time. You will also begin to see monthly savings in energy bills, but there are other ways that solar panels pay you back. Those include:
1. Adding value to your home or commercial building 
2. Monthly decreases in energy costs
3. The ability to add more energy appliances without increased monthly costs
4. The potential for tax credits for going solar

Can solar panels power a house 24-7?

Most definitely! Solar panels can certainly power a house 24-7, with the addition of a high-quality inverter and a suitable battery bank, of course. To power, a house under normal usage will require a massive solar array, though, and there will be a very expensive initial financial outlay.

Do I need to tell my energy supplier I have solar panels?

This depends on where you live, but in most cases, it’s not necessary to inform your energy supplier that you have solar panels. That said, you may be producing excess power with your solar system, in which case you may be able to sell that excess power back to energy companies.

In this case, you’ll naturally need to be in contact with them. 

What Are Solar Cells Known as and Why?

Solar cells are also called photovoltaic (PV) cells. They are called so because the term ‘photovoltaic’ literally means light i.e. photo and electricity i.e. voltaic.

These cells generate electricity through the photovoltaic effect. This effect basically causes the generation of free electrons from the semiconducting silicon material of the solar panel when sunlight hits its surface.

What Type of Solar Panels Are Most Efficient and Why?

There are currently three types of solar panels available in the market that are:
1. Monocrystalline
2. Polycrystalline
3. Thin-filmed

Among these, monocrystalline solar panels are known to be the most efficient among all others.

Does heat enter your home through the roof?

Absolutely. Heat enters your home through your roof, and on a hot day your attic can get up to 150 degrees Fahrenheit or more. Through conduction, heat from the sun warms your roof which then warms your attic and the rest of your home.

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