Do I Need A Battery For My Solar?

Learn More About Energy Storage And Find Out If It’s Right For You.

Picture of page author Alex Kelleher.

by Alex Kelleher
5 min read - Published on 05/10/2022

One of the motivating factors for homeowners who switch to solar is the empowerment that comes from making power personal. When your home provides its own clean energy, it is less taxing on the grid and gives you energy independence. However, in order to be completely independent from your utility company, you’ll need to include a battery backup to your solar system.

While a battery backup is not required to go solar, it can be a beneficial addition for many homeowners. Batteries store excess energy from your system that can be used during times when your panels aren’t producing enough electricity. This includes nights, cloudy days, or during peak energy usage hours. Batteries are especially critical for those who can’t afford a lapse in electricity in things like medical equipment, appliances and more.

A battery can add a good chunk to your loan, but the security it provides can be well worth the cost to many people. Find out more about batteries and if they’re right for you in this article.

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How Do Solar Batteries Work?

Your panels are constantly converting as much sunlight into electricity as possible. The photovoltaic cells in the panels convert heat from the sun into direct current (DC). The DC electricity then goes through your inverter to convert to alternating current (AC) which is the most common type of electricity used in your home. The AC electricity runs from the inverter directly into your home to power your appliances, lights, electronics and more.

When all your power needs have been met but there is extra power being generated by your solar system, the energy needs to go somewhere. That’s where a battery comes in. The energy flows either straight from the panels to your battery (if it is DC coupled storage), or waits to be stored in your battery after going through the inverter (if it is AC coupled storage). The energy is stored there until your home needs more energy than it is producing and will pull from the power from the battery.

Most solar batteries are lithium-ion, like the battery in your smartphone and other handheld electronics, but there are also lithium-iron phosphate, lead acid, nickel cadmium and flow batteries.

Types of Batteries

Lithium-ion Batteries

Lithium-ion batteries store chemical energy before converting it into electrical energy. This conversion happens during a chemical reaction where lithium ions release electrons that flow from the negatively charged anode to the positively charged cathode. The lithium-salt electrolyte found in the battery is a liquid that balances the reaction and provides the required positive ions to encourage this flow of electrons, which is what creates electricity.

The lithium ions flow across the electrolyte back to the positive electrode when you’re ready to pull electricity from the battery. The outer circuit also allows electrons to move from the negative anode into the positive cathode, powering the device.

Lithium ion solar storage batteries for your home use this to initiate the process of creating an electrical current by combining multiple of the ion battery cells with technology that regulates the performance of the battery.

Lithium Iron Phosphate Batteries

These batteries are similar to lithium ion batteries but use lithium iron phosphate as the positively charged cathode and typically graphite as the negatively charged anode. The chemical stability helps these batteries have increased life spans, efficiency and safety.

Most lithium iron phosphate batteries have four battery cells with 3.2 volts each. These cells are wired in series and, when connected, create a 12-volt battery.

Lead Acid Batteries

A lead acid battery uses technology that is almost 200 years old and is still popular due to their cheap and reliable nature. This battery uses a chemical reaction between lead, water, and sulfuric acid to store the electrical energy.

While this is a reliable option, newer technology can be more cost-effective and compact for your home.

Nickel Cadmium Batteries

In nickel cadmium batteries, nickel oxide hydroxide is used to make a positively charged cathode, while metallic cadmium is used to make a negatively charged anode.

These batteries can be more costly due to the higher cost of manufacturing associated with the toxic chemicals. They also suffer from “memory effect” where they fully charge after a series of full discharges.

Flow Batteries

Flow batteries pump fluids containing active materials through the cell to promote reduction/oxidation of both sides of the ion-exchange membrane to result in electric potential. The electro-active material in a battery that does not have bulk flow of electrolyte is stored within the electrodes. For flow batteries, however, the energy component of the battery is dispersed in the electrolyte. The electrolyte is kept in external tanks with one tank usually corresponding to the negative anode and another to the positive cathode.

There are two different processes your energy can go through when a battery is included in your system. The electricity flows either straight from the panels to your battery and passes through an inverter when being pulled out, or goes through the inverter before being stored in your battery.

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DC Coupled Storage

A DC coupled storage system takes the DC electricity produced from your panels directly to the battery where it's stored. When you’re needing to use the battery-stored electricity, the DC electricity in your battery will go through the inverter to change it to AC to be used in your home. This process creates more efficiency as the energy from your panels will only be inverted once (from DC to AC).

AC Coupled Storage

Alternatively, an AC coupled storage system holds stored AC electricity. This means that the DC power from your panels uses the inverter to change to AC electricity to be used in your house. Once your house reaches the needed energy, the excess AC goes through another inverter to convert back to DC electricity before being stored. When the battery is needed, the DC will change again to AC to be used in your home. This process means electricity that is stored in the battery will be inverted three times before being used—not super efficient.

Benefits of a Battery

  • Protects you against any lapse in power
  • Maintains your ownership of excess power before sending it back to the grid
  • Makes you less reliant on the grid
  • Makes your utility bill even smaller
  • Makes you less likely to pay higher fees from utility company during peak usage hours
  • Provides security for your home and family

Alternative to a Battery

While adding a battery to your solar system can be advantageous for many reasons, it can be an additional cost that some would rather forgo. If this is the case, the excess power being generated by your solar panels—but not needed by your home—gets sent back to the grid and helps provide clean energy to your neighbors. Your utility company will “pay you” for the energy by providing you with credits that can be used to buy energy from them when your panels aren’t producing enough electricity.

Why Would I Need A Battery Backup?

Batteries are a great addition to your solar energy system if you can’t afford to have a lapse in power. Backup batteries make it possible to protect your home from outages for as long as you can stretch the stored power to maintain heat or air conditioning in your home, make sure all your devices are charged (to keep in touch with worried loved ones), keep life-saving medical devices powered, or charge any electric vehicles you may have.

Adding a battery can help homeowners feel secure during a time of uncertainty surrounding the power grid. Having a battery provides peace of mind that your power won’t stop just because your neighbor’s did.

Learn More

Battery backup systems can be an added comfort for homeowners who want the safety of not relying on the power grid in the event of an emergency. While they’re not for everyone, they are worth having a conversation about to see if they are right for you. Talk to one of Lumio’s solar experts today to see if a battery backup is a good addition to your solar project.