Find the Best Battery for Your Solar Power System Part 2

In part 1 of evaluating solar power batteries, we discussed how to compare your solar-powered system storage options based on the capacity and power, the depth of discharge (DoD), round-trip efficiency of solar energy, the lifetime of a solar power battery and the warranty. In part 2 we are going to be discussing the other factors that will need to be evaluated when it comes to solar-powered systems storage options.

How Long Will Solar Batteries Last?

There are two ways to answer the question of how long the batteries for solar-powered systems will be able to provide solar power to your home. In most cases, a fully charged solar power battery is going to be able to run your home overnight when your solar panels aren’t producing enough solar energy. To make a more precise calculation, you are going to need a few more variables, including how much energy your household consumes in a given day, which the capacity and power rating is for your solar power battery and whether or not you are connected to the electric gird.

For the sake of a simple example, we are going to need to determine the size of the battery that is needed to provide an adequate solar plus storage solution with national average data from the U.S. Energy Information Administration. The U.S. household will use roughly 30 kilowatt-hours (kWh) of solar energy per day and a typical solar power battery can deliver some 10 kWh of solar energy capacity. A simple answer would be, if you purchased three solar power batteries, you could run your home for an entire day with nothing but battery support.

But the reality is, the answer is going to be more complicated than that. You are also be generating solar electricity with your solar-powered system during the day which will offer strong solar power for around 6-7 hours of the day during peak sunlight hours. On the other end, most solar power batteries cannot run at maximum capacity and generally peak at a 90 % DoD. As a result, the 10 kWh solar power battery is going to likely have a useful capacity of 9 kWh.

Ultimately, if you pair your solar-powered system with a solar power battery, one or two batteries can provide a sufficient amount of solar power during night time, when your solar panels aren’t producing. Buy, without sources of renewable energy solution, you might need around 3 batteries or more to power your whole house for 24 hours. Additionally, if you are installing a solar system with batteries for home use to go off-the-grid, you should install a few day's worth of backup solar power to account for days where you might have cloudy weather.

Solar Battery Lifespan

The general range for solar power battery’s useful lifespan between 5 and 15 years. If you get a solar power battery installation today, you will quite possibly need to replace it at least once to match the 25 to 30-year lifespan of your solar-powered system. However, like the lifespan of solar panels has significantly increased in the past decade, solar energy batteries are expected to follow suit as solar power batteries grow in popularity.

By maintaining your solar energy batteries properly, it will have a significant effect on your solar battery’s lifespan. Solar power batteries are vastly impacted by temperature, so protecting your battery from freezing and torrid temperatures can also increase its useful life. When a solar power battery drops below 30° F, it is going to require more voltage for the solar power battery to reach its maximum charge; when the same batter rises above 90° F, it is going to overhear and will the require a reduction in charge. To solve this issue, many leading solar power battery manufacturers are going to provide temperature moderation as a feature. But, if the battery that you end up purchasing doesn’t provide the feature, you are going to need to consider other features such as earth-sheltered enclosures. Quality maintenance efforts can impact how long your solar energy battery is going to last.

What are the Best Batteries for Solar-Powered Systems?

The solar energy batteries that are used in home energy storage is typically going to be made with one of three chemical compositions: lead-acid, lithium-ion, and saltwater. In most cases, lithium-ion batteries are the best option for a solar-powered system, though other solar power battery types can be affordable.  

Lead Acid

Lead-acid batteries are going to be a tested technology that has been used in off-grid energy systems for decades. While they have a relatively short life and lower DoD than other battery types, they are also one of the least expensive options currently on the market in the home solar energy storage sector. For homeowners who are looking to go off the grid and need to install a lot of storage for solar electricity, lead-acid can be a good option.

Lithium-Ion 

Most of the new home energy storage technologies, such as the use of some form of lithium-ion chemical composition. Lithium-ion batteries are lighter and more compact than lead-acid batteries. They also have a high DoD and longer lifespan when comparing them to lead-acid batteries. But,lithium-ion solar power batteries are more costly than their lead-acid counterparts.

Saltwater

A newcomer in the home solar energy storage industry is the saltwater battery. Different than other home energy storage options, saltwater batteries don’t have heavy metals, relying instead on saltwater electrolytes. While batteries that use heavy metals, including lead-acid and lithium-ion batteries, need to be disposed of with special processes, a saltwater battery can be easily recycled. But, as a new technology, saltwater batteries are going to be relatively untested, and the one company that makes solar power batteries for home use (Aquion) filed for bankruptcy back in 2017.