Where Does Solar Power Go When Batteries Are Full?

Solar panels can generate enough renewable energy to keep your entire home powered. But there can be times when it generates more power than needed. So where does solar power go when the batteries get full?

The short answer is that the charge controller diverts extra power. Where this power goes depends on your solar setup. If you have an off-grid application, then the inverter receives any extra electricity. The inverter converts the DC power to AC power. This can then be used by any load connected to the circuit. However, the solar panels will only generate enough energy to match all available loads connected to it.

In a grid-tied solar system, the inverter would send the AC power to the home first. If the home does not have enough load to utilize all of the electricity coming from the inverter, it can begin to push the remaining electricity back to the grid.

The amount of power pushed to the battery varies depending on what stage of charging it is in. The battery will continue to trickle charge when it is fully charged. We’ve detailed all of the nuances that direct how the electricity routing takes place in the rest of the article below.

What Happens To Excess Solar Power Generated

You probably have a solar system. And you are worried that your batteries can be damaged with too much power from your solar panels. So what happens to the excess solar energy when the rechargeable batteries are at capacity?

Check out the best 20 rechargeable batteries for solar systems.

Thankfully, the charge controller and inverter act as a quarterback for the whole system. The battery can overheat and have a shorter lifespan if it were to overcharge. The solar charge controller helps regulate the energy routing from the solar panels to the battery.

It cuts off current flow from the batteries to the solar panels when sunlight isn’t available. Similarly, the charge controller limits current flow to the battery when it is fully charged. It will let some electricity continue to flow so the battery can trickle charge to keep a 100% charge.

The charge controller directs the extra electricity around the battery to the actual loads when the solar panel produces excess energy. Of course, it will go through the inverter first. The inverter convert the direct current to alternating current. The solar panels will never generate more electricity than needed by the connected loads. This prevents any overcharging or short circuiting downstream.

Generating renewable energy is the easy part. Directing it where to go at the right time is the hard part. That is why the charge controller is so important. But there are other components to a grid-tied or off-grid solar system that make everything work like clockwork.

Where Does Solar Power Go When Batteries Are Full?

Before diving into where solar power goes when batteries are full, we should look at the two main types of solar energy solutions. The first type of solar system connects to the grid. On the other hand, the second system does not connect to the grid at all. Each of these systems behave a bit differently, as detailed below.

How A Grid-Tied Solar Energy System Works

There are a number of components that help a grid-tied solar energy solution power a residential home. Here’s a quick snapshot of what each of those components do:

  • Solar panels – generate the electricity
  • Array DC disconnect – disconnects the solar panels from the charge controller for maintenance
  • Charge controller – also known as the charge regulator, responsible for maintaining the proper amount of electricity charge of the batteries
  • Inverter – converts the direct current to alternating current
  • Battery pack – storages energy generated by the solar panels for later use
  • Utility meter – measures how much electricity (kWh) the house uses and generated by the solar panels
  • Breaker panel – controls the flow of electricity between the house and the grid
  • Transfer switch – controls whether the house is getting electricity from the batteries, solar panel, or grid

The solar panels convert sunlight into electricity and send that energy to the charge controller. The charger controller is responsible for continuously charging the batteries. The batteries will trickle charge from the charge controller when they are completely full. The inverter receives all of the excess energy.

The inverter converts the direct current into alternating current. Appliances and other loads in a house need this kind of electricity. Any electricity produced in excess of what the batteries and house can use will be sent back to the grid through the utility meter. Depending on the tariff structure, the utility may even pay you for the additional electricity put back on the grid through something called net metering.

Where Does Solar Power Go When Batteries Are Full In An Off Grid Solar Energy System?

The off grid solar storage system has a lot of the same components as the grid-tied solution. The only addition is a off-grid generator that continues to provide power when the solar panels and batteries cannot.

The solar panel is connected to the DC disconnect switch, which allows the solar panels to disconnect for maintenance. The charge controller feeds the right amount of electricity to the battery bank at the right time. It can also bypass the battery and send some electricity straight to the meter. The batteries can also be powered by a backup generator when the sun isn’t shining.

The meter measures acts as a toll road for the electricity coming from the battery bank or the charge controller. It measures how much comes through before hitting the main load disconnect switch. This switch can stop electricity from entering the inverter.

So where does solar power go when batteries are full?

The inverter is the last step the electricity has to take before entering the breaker panel. It’s this piece of equipment’s job to convert the electricity from AC to DC so that household appliances can use it. This inverter feeds the breaker panel, which splits the electricity up into different loads that are spread throughout the house. These loads will end in either a plug or an outlet. Either of which provide the necessary energy to power the equipment and loads throughout your house.

How Do I Know When my Solar Batteries Are Fully Charged

The charge controller takes care of regulating how much electricity your batteries get so that you don’t have to. It will automatically adjust the amount of energy supplied to the batteries based on where they are in their charge cycle. When the solar panels have fully charged the batteries, the charge controller will reroute most of the electricity directly into the inverter instead of the batteries.

A solar monitoring system could be installed to record and monitor every detail of your energy generation. It will report on a variety of things, such as electricity generated and the status of your batteries. Many smart inverters come with a solar monitoring solution already installed. But those solutions typically only report on things happening to and around the inverter. So, it can miss what is going on with the battery packs.

However, there are smart batteries available on the market today that come connected to the web. They often have their own app that reports on the battery status, charge status, and current operational status. These advanced solutions can let you know exactly how much of the battery has been charged and where it is in the charging process.

What Happens To Solar Panels With No Load

The inverter will always sense a load when it is connected to the solar panels. However, it will not have a load if the DC disconnect switch is disconnected. In this case, the solar panel will treat it as an open circuit. Since it is an open circuit, the solar panels will stop transferring electrons. The current will go to zero, which means the power will go to zero. Power is the voltage multiplied by the current.

In short, the solar panels will stop generating electricity when the load is disconnected. There is no need to cover the solar panels to protect them against the sunlight. They will simply stop working.

If your solar panels do not have a load because of a broken wire, it’s easy to fix a broken wire on your own.

Can I Leave Solar Panels Unplugged?

If you would like to disconnect your solar panels from the load or battery, you can use the DC disconnect switch to do so. This will safely “unplug” the solar panels. You can leave them in the unplugged state for as long as you would like. It will not damage them or cause them to overheat. As long as the load is disconnected, the solar panels will not generate electricity.

There is nothing wrong with keeping the solar panels unplugged. However, you should consider covering them to protect them against the weather if they are not in use. Strong wind can bring branches and other debris into the solar panels causing cracks or damage. In some geographies, hail can damage the solar panels as well.

Should I Cover Solar Panels When Not In Use?

You do not need to cover your solar panels while they are not in use. This will not prolong the life of the panels. The sun will not cause a chemical reaction if they are not being used by the battery or another load. However, severe weather can cause damage to your solar panels whether they are in use or not. Since they are not in use, you should consider a solid cover to protect against inclement weather.

You may decide not to cover your solar panels. After all, they are manufactured to be durable in the strongest weather. Remember that most solar panels are warrantied against harsh weather events for up to 25 years. So, if you don’t cover your solar panels when they are not in use, you could still be covered by the warranty.

Have a pond or pool that uses a pump? You can easily convert that pump to a solar pond pump.


I'm trying to make the world a bit greener every day, whether that's through my day job or helping others make green choices for their homes.

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