How Long Do Solar Batteries Last?

The lifespan of a modern solar battery is, on average, 10-15 years. Some battery types have shorter life cycles but are considered old battery technology. Ultimately your solar battery will be affected by factors such as type, quality, and usage conditions.

🔑 Key takeaways

1️⃣ While Lead acid batteries and related technologies represent the cheapest upfront cost, over twenty years, they will have to be replaced +- 4 times, which makes them the highest cost option in the long term.

2️⃣ Lithium-ion is the most commonly used technology, and while it is more expensive at the installation stage, the batteries will last +15 years, making it the most affordable option.

3️⃣ Other technologies offer potential; however, they have been overshadowed by the benefits of Lithium-ion.

Most solar systems have four primary components – the solar panels, the inverter, the charge controller, and the batteries used to store the energy. The batteries represent the highest cost of the four components and have the shortest lifespan.

This means the system’s budget should be based on the estimated 20-year cost rather than the immediate upfront installation charges.

⏳ How Long A Solar Battery Lasts Depends On The Battery Type

There are several types of batteries available for use in a solar system. Two factors largely determine the suitability of different battery technologies used for solar power.

Depth Of Discharge

The depth of discharge (DOD) that the battery will tolerate.

If the battery is regularly discharged below the depth of discharge, then damage will occur, and the battery life will be severely shortened.

If the DOD is 60%, you can only use 60% of the battery’s rated capacity.

This means that if the battery has a DOD of 60% and the battery is rated at 500 amp-hour capacity battery, there is only an effective 300 amp-hours available.

Durability

Solar battery durability can have a significant impact on its lifespan. Factors that can affect the durability of a solar battery include:

Quality of materials: The quality of the materials used to construct a solar battery can affect its durability. Batteries made with high-quality materials are less likely to suffer from wear and tear and will have a longer lifespan.

Temperature: The operating temperature of a solar battery can affect its lifespan. Batteries exposed to extreme hot or cold temperatures are more likely to degrade quickly and have a shorter lifespan.

Exposure to the environment: Solar batteries exposed to harsh environments, such as high humidity or salt water, are more likely to degrade quickly and have a shorter lifespan.

🔋 The Types Of Batteries Available

The different available battery technologies are listed below.

Lead-Acid Batteries.
Absorbent Glass Matt (AGM).
Gel Cell Batteries Hydrogen batteries
Lithium-Ion Battery
Nickel-Cadmium (NICAD)
Red-ox flow batteries
Sodium Batteries (Saltwater )

Lead Acid Battery

A lead acid battery consists of lead and oxide sheets placed in sequence in the battery.

The battery is filled with an electrolytic solution of sulfuric acid and water (called an acid pool).

The current flows from the lead sheet (called an anode) to the oxide sheet (called a cathode).

The acid causes the lead sheet to give up electrons (units of electrical current) which is accepted by the lead oxide sheets.

Each lead and lead oxide sheet combination produce 2 volts, and 6 pairs laid together will produce 12 volts.

It discharges when the battery is connected to a current consumer (light bulb, etc.).

When discharge occurs, the lead sulfate is formed and cakes each sheet. If the battery is discharged a few times beyond its depth of discharge rating (50%), the layer of lead sulfate becomes thicker and ultimately won’t accept a recharge.

The expected lifespan of a lead acid battery is 3-5 years.

Lead Acid Battery batteries are solid and can be used in mobile applications.

Absorbent Glass Matt (AGM)

Absorbent Glass Matt (AGM) batteries use a similar technology to conventional lead acid batteries; however, the AGM batteries have an absorbent glass matt (hence the name) placed between the two plates (positive and negative.)

The glass matt is an absorbent material containing the electrolyte, stopping it from sloshing between the cells. This prevents spills and reduces acid loss during use.

This enables the manufacturers to call an AGM battery “maintenance-free.”

The chemistry using lead, sulfuric acid, and water to produce current is replicated in an AGM battery.

The difference between an AGM battery and a conventional one is the thin sheets of glass matt installed between the battery’s plates.

The recommended depth of discharge for a lead acid battery should not be more than 50%.

The expected lifespan of a lead acid battery is 5 years.

Absorbent Glass Matt batteries are durable and can be used in mobile applications.

Gel Cell Batteries

Sometimes called valve-regulated lead acid batteries (VRLA). Gel Cell batteries use the same chemical process as lead acid batteries.

The technology is different from Lead Acid batteries in two respects.

They use silica (sand) to convert the sulphuric acid (the electrolyte) into a thick gel-like liquid, preventing battery acid spills.
The internal structure is different, and gasses are not vented out of the battery and are instead recombined within the battery. This increases battery efficiency while also making them more eco-friendly.

The depth of discharge of a gel battery is 50%.

The expected lifespan of a gel cell battery is 6 years.

Gel Cell batteries are very durable and can be used in mobile applications.

Lithium-Ion Battery

The following describes the basic working of a Lithium-ion battery.

Lithium-Ion Batteries include the following components:

An anode.
A cathode.
A separator.
An electrolyte.
Positive and negative collectors.

The cathode and anode store the electrical current. When an electrical current is drawn from the battery, the electrolyte transports the positively charged ions from the anode, across the separator, to the cathode.

As the ions move, electrons are generated at the positive collector, which powers the electrical consumer.

The process is reversed when the battery is recharged.

Lithium-ion batteries weigh less, last longer can be discharged to 15% without any degradation in capacity.

They must be kept in a stable, protected area because they are easily damaged.

Nickel Cadmium (NICAD) Battery

NICAD batteries use nickel oxide at the cathode (positive) and cadmium at the negative electrode.

The technology uses potassium hydroxide solution as its electrolyte.

When the battery is discharged, the chemical composition of the cathode is transformed from nickel oxyhydroxide [NiOOH] to nickel hydroxide. In the anode, the cadmium is transformed into cadmium hydroxide.

When the battery is recharged, the process is reversed.

The result of the chemical reaction is the release of electrons which are used to power a circuit.

NICAD batteries are very durable and can be used in mobile applications.

Red-Ox Flow Batteries

Red-Ox batteries use a naturally occurring reaction involving the transfer of electrons during an oxidation-reduction reaction.

The substance which loses the electrons (anode) is said to have Oxidized, and the substance which receives the electrons (cathode) is reduced.

The cathode and anode are immersed in two different solutions (electrolytes). A salt bridge and a conductive wire connect the solutions.

Redox batteries are expected to last for at least 16 years. They can also be fully discharged and recharged (DOD – 0%) with no adverse effects.

Sodium (Saltwater) Batteries

Sodium batteries use a concentrated saline solution (6 parts salt to 1 part water) as the electrolyte.

Saltwater batteries work similarly to other ion batteries; the main difference is they use salt water as the electrolyte. As a result, power output per cell is relatively low.

As with all batteries, the electrolyte captures, stores, and eventually discharges the electronic energy (electrons).

Saltwater batteries can be discharged at 100%

Saltwater batteries can be expected to last for ten years and will generally manage 5,000 charge/discharge cycles.

Saltwater batteries are very durable and can be used in mobile applications.

📝 Summary Of Each Battery Technology Expected Lifespan

The following lists the summary of each battery’s expected lifespan, as well as the current (2023) cost of replacement

Battery Type	Depth Of Discharge	Expected Lifespan	Number Of Charge/ Discharge Cycles	Unit Cost
Lead Acid	50%	3 years	400	$150 (0.2kw)
Absorbent Glass Matt (AGM).	50%	5 years	2,000	$350 (0.2kw)
Gel Cell	50%	6 years	1,000	$350 (0.2kw)
Lithium-Ion	85%	15 years	10,000	$ 2,690 (3.8kw)
Nickel-Cadmium (NICAD)	85%	15 years	10,000	TBA
Red-ox flow batteries	100%	16 years	6,000	$5,700 (3.8kw)
Sodium (Saltwater)	100%	10 years	5,000	$2,200 (2.5kw)

🙋‍♂️ FAQs

How Do Batteries Work?

All battery cells have one thing in common – they all require three components:

A Positive electrode (Cathode)
A Negative electrode (Anode)
Electrolyte

Each technology uses an electrolyte to use a chemical reaction to release electrons at the positive electrode, which the negative electrode accepts.

A battery may consist of several cells linked together, or it may be a single cell.

The differences are in the materials/substances used for each component.

How Much Does It Cost To Replace Solar Batteries?

The cost of replacing solar batteries will depend on the battery technology you use for your solar system.

Lead acid, AGM, and Gel Cell batteries may be cheaper; however, when factoring in the power capability and the fact that they don’t last as long as other types, they are not as efficient as may be seen.

In 2023 the cost of batteries that can produce 5kw is as follows.

Battery Type	Number of batteries to produce 5 kW	The total cost of batteries	Cost per kW	Number of batteries in 20 years	Cost over 20 years (2023 prices)	kW cost over 20 years
Lead Acid	25	$3,750	$0.75	166	$24,900	$4.98
Absorbent Glass Matt (AGM).	25	$8,750	$1.75	100	$35,000	$7.00
Gel Cell	25	$8,750	$1.75	84	$29,750	$5.95
Lithium-Ion	2	$5,380	$1.07	3	$8,070	$1.61
Nickel-Cadmium (NICAD)	1	TBA	TBA	1	TBA	TBA
Red-ox flow batteries	2	$11,400	$2.28	3	$17,100	$3,42
Sodium (Saltwater)	2	$4,400	$0.88	4	$8,800	$1.76

How Do You Prolong The Life Of A Solar Battery?

You can do several things to improve the life of the batteries and not have to depend on a backup system.

Never overcharge or discharge the batteries: Set the system inverter to cut the power supply once the depth of discharge value has reached.

Similarly, ensure that the inverter or charge controller stops charging once the battery is 100% charged.

Limit the number of batteries: This would generally not apply to Lithium-ion, Nickel-Cadmium (NICAD), Red-ox flow batteries, and Sodium batteries because there are fewer needed in a system.

The more connections there are, the greater the current loss through resistance. With the other battery types, ensure that there are no more than 16 batteries in each bank.

Rotate the batteries: If you use Lead Acid, Absorbent Glass Matt (AGM), and Gel Cell batteries, change the positions of the units in the circuit regularly.

This will help balance the load and ensure no battery carries an unequal value.

How Often Do Solar Batteries Need To Be Replaced?

Batteries need to be replaced when they cease to be able to receive a full charge and become discharged in an unacceptably short time.

🔑 Key Takeaways

The life expectancy of a home solar battery depends on the battery technology you install into our solar system.

The conservative estimate of a solar battery’s life expectancy ranges between 3 to 15 years.

1️⃣ Lithium-ion is the most commonly used technology, and while it is more expensive at the installation stage, the batteries will last +15 years, making it the most affordable option.

2️⃣ Ensure your battery warranty is long enough for the expected life cycle of the battery type.