solar battery backup system

Many solar panel users look to store the excess energy for their home. This is great as a backup in case of a power outage, or as an option to power the home overnight when the panels do not receive any sunlight. 

They also help reduce electricity rates from the grid!

Although solar battery storage can be expensive, many solar panel system owners choose this option. This is especially true for those whose homes are off grid.

But the question is: how long do solar batteries last?

In general, you can expect solar batteries to have a lifespan ranging from 5 to 20 years.

The exact lifespan will depend on factors such as the expected life of the battery, the warranty, and how often the battery is used.

So there are many options! We've done the research for you, so read on to find out more about solar batteries.

What are the best batteries for solar?

There are 3 types commonly used in energy storage. These include Lead-acid batteries, lithium-ion batteries, and saltwater batteries.

Lead-Acid battery

Lead Acid Batteries

Lead-acid batteries used for solar energy storage are also known as "deep cycle batteries". They exist in two forms: flooded lead-acid and sealed lead-acid batteries, which cost more.

They are largely used in solar systems, especially off-grid systems. Lead-acid batteries have a stellar track record for solar power storage.

The advantage of lead-acid batteries is that they are quite safe and highly reliable. However, compared to lithium-ion batteries, they have a shorter lifespan and require regular maintenance.

AGM battery

AGM is a variant of a sealed lead-acid battery, having a more advanced design.

These versatile batteries can't leak, operate better across temperature extremes and have enhanced discharge and recharge efficiency. They are popular for solar systems.

Lithium-Ion batteries

Parts of a lithium-ion battery

These batteries are extremely popular, mainly because of their high storage capacity. This is aided by their high energy density and efficiency.

Lithium-ion batteries are lighter and more compact compared to lead-acid batteries. They also have a higher Depth of discharge (DoD) and a longer lifespan.

However, these batteries generally are more expensive than their lead-acid counterparts. 

In terms of maintenance, lithium-ion compares favorably to other battery units. 

Advances in the storage capacity of lithium-ion batteries had led to them becoming the 'go to' battery for many everyday devices.

Saltwater Battery

how a salt water battery works

Saltwater batteries are a fairly new battery technology with a promising future. Homeowners have been deploying them for residential solar panel systems for energy storage.

Saltwater batteries rely on saltwater electrolytes. The saltwater solution captures, stores, and discharges the solar energy.

The advantages of saltwater batteries include ease of recharging, safety, and a long lifespan.

They also have relatively high Depth of discharge rates, similar to lithium-ion batteries. This is advantageous because saltwater can also be recycled with no special processes needed.

Saltwater batteries are definitely one to watch as development continues!

What are the factors that affect the solar battery lifespan?

When homeowners decide to invest in solar systems, a major concern is energy storage. A critical component of any solar power system is the capability to store energy. Depending on the energy needs of a home, when a PV system is installed solar batteries are vital to ensure proper supply of electricity to the home.

Some factors that affect the life of a solar battery include:

The solar battery type

We know that there are different solar battery storage options on the market, with different chemical compositions. As discussed above, these include lead-acid, lithium-ion, and saltwater batteries.

Lithium-ion batteries or a saltwater battery will both last longer than a lead-acid battery.

Depth of Discharge (DoD)

DoD specification is important because it affects the battery usage and therefore how long it will last.

DoD refers to what degree a battery is discharged relative to the total storage capacity. It is usually represented as a percentage. A battery at 100% DoD means that it is fully discharged. 

  • If a battery has a capacity of 10 kWh and discharges to 3kWh , the DoD is 70%. 

As batteries get charged and discharged, they gradually degrade.  Deeply discharging or discharging to 100% can shorten the lifespan of some batteries. Over time, their efficiency at storing solar energy reduces.

The depth of discharge of batteries varies from one type of battery manufacturer to another.

Prospective buyers of a solar system with battery add-ons, should check the manufacturer's specification for the recommended DoD.

Round-trip efficiency

Round-trip efficiency is the difference between the amount of energy used to charge a battery and the available amount of energy.

A battery with high round-trip efficiency will mean that you get more economic value from your battery.

Use cycle of the solar battery

The longevity of a solar battery is determined by its usage cycles. For example, a lead-acid option may offer between 300-700 cycles while lithium ion batteries are capable of several thousand cycles.

Warranty

A battery's performance degrades with time. A good warranty ensures that the cycle maintains its storage capacity levels throughout the warranty period, and the manufacturer should replace it if performance drops.

Battery temperature

Environmental temperatures, either hot or cold, can have an impact on the solar battery and your solar power systems in general.

Your solar batteries should be protected from sweltering temperatures or freezing conditions so they will last longer.

If temperatures drop below 30 degrees, many batteries will require a lot of voltage to perform to their fullest.

On the other hand, when temperatures rise above 90 degrees, batteries can overheat. Therefore, maintaining the optimal room temperature is essential if you want your solar battery to have a long lifespan.

Solar battery maintenance

WORKER MAINTAINING A SOLAR BATTERY

The primary goal of battery systems maintenance is to increase the performance of the battery and increase its lifespan.

Safety precautions should be practiced when cleaning the battery and replacing the solar battery.

Some of the basic ways to maintain your  solar battery system include:

Programming the solar battery system

When your solar system battery pack comes online, you can configure the voltage set points and charging voltage. The charging voltage is key for proper charge cycles.

Cleaning the batteries

CLEANING BATTERIES

Battery terminals require regular cleaning using a mixture of distilled water and baking soda. Use the special terminal cleaning brushes for this job.

Tuning the solar battery

You can increase the life expectancy of a solar battery by reducing the number of batteries being used at a bank. This helps to reduce the resistance and number of connections, and should lead to more even charging.

Enhance equalization on solar batteries. This process ensures charging of the solar battery is regulated and avoids uneven charging which leads to plate sulfation.

Always ensure that the solar battery does not spend long periods of time uncharged. If the battery is hooked-up to a solar panel, this should not be an issue as there would be a continuous flow of solar energy.

Replacing the solar battery

Ensure that you follow the manufacturer's safety measures and instructions when replacing the solar battery at the end of its life.

Avoid mixing old and new batteries to prevent the new batteries degrading to the level of the old batteries. This will reduce the performance of your solar energy system.

How to choose the best solar battery

Using the correct type of solar battery will help ensure it is fit for purpose and lasts as long as the manufacturer intended.

Ignoring the budget for a moment, the best way to select a good solar battery is to take the following into consideration.

Capacity and power

Capacity is the total amount of electricity that a solar battery can store.

In solar batteries, a power rating is the amount of electricity that a battery can deliver at one time.

Therefore, batteries with a high capacity and a low power rating would deliver a low amount of electricity for a long time.

A battery with low capacity and a high power rating could run your entire home, but only for a short time. 

Manufacturer

Eco Worthy Battery

Companies such as Eco-Worthy and Renogy manufacture different battery products which are suitable for use with solar panels.

Some states are also encouraging the uptake of solar energy systems and offering deals with manufacturers. You may get tax credit if you install solar panels together with certain battery types! Check local information to see what is available in your state.

Battery manufacturers produce battery types to be used in various solar energy systems. Ensure you choose the one that is suitable for your needs, either home or industrial.

Battery life and warranty

It is always wise to consider how long the battery will last. Solar batteries will have a warranty that guarantees a certain number of cycles and/or years of useful life.

Battery performances naturally degrade over time but most manufacturers will guarantee a battery's capacity over the course of the warranty.

Wrap up

As you have seen above, there are many options when considering what batteries to use with your solar panel system at home.

The solar battery storage you choose will depend on factors such as your storage needs, your budget, and the power output of your solar panels.

Many solar panel manufacturers also offer batteries as part of a complete kit. This gives you reassurance that the energy storage will be suitable for the power generated.