Battery Comparison

#1 Battery Life

The life span of your solar battery is dependent on two things: Life cycle and age.

  1. Life Cycle: When you discharge a battery by using it’s power, and then charge it back up again, that is referred to as one charge cycle. The number of charge cycles your battery can handle before it begins to degrade is dependent on the type and quality of battery, as well as depth of discharge (see #2 Depth of Discharge).
  2. Age of Battery: Your battery will degrade over time even if you’re not using it.

(More information on battery life and capacity loss can be found here).

#2 Depth of Discharge (DoD)

Depth of discharge refers to how much overall capacity is used before recharging the battery. For example, if you use half your battery’s capacity, the DoD would be 50%.

Every battery has a life cycle dependent on the depth of discharge. For example, a true deep cycle AGM battery will have a life cycle of 350 cycles at 100% DoD OR a life cycle of 3,500 cycles at 10% DoD. This means you can cycle the battery at 10% DoD every day for 9 1/2  years OR cycle it 100% for one year before affecting the life of the battery.

(More about Depth of Discharge can be found here).

#3 Efficiency

Simply put, efficiency of your solar system is how much of your solar power is actually being stored and used.

As an example, FLA batteries are only 80-85% efficient depending on the type and condition. That means, if you have 1,000 watt hours of solar coming into the batteries, only 800-850 watt hours are available after charging and discharging.

Lithium and AGM batteries are more than 95% efficient. Using the same example, you’d have over 950 watt hours of power available, as compared with the Flooded Lead Acid batteries.

Depending on the configuration of your system, higher efficiency could mean getting the same amount of energy use and storage in a smaller system, thus saving you more money in the long run.

#4 Cost

There are two costs you need to consider when doing an off grid system: Upfront cost and long term cost. Many people are so focused on the upfront costs that they don’t think about any long term costs that can affect their decision of battery storage.

Upfront cost is what you initially pay for your battery bank. Long term cost is what you end up paying for batteries throughout the life of your system.

Lead-Acid vs Lithium-Ion Batteries

Lead-Acid Batteries

Lead-acid batteries have been used to provide backup power for solar homes since the 1970s. While they’re similar to conventional car batteries, the batteries used for home energy storage are called deep-cycle batteries since they can be discharged and recharged to greater levels than the batteries in most cars and trucks.

Lead-acid batteries are significantly cheaper upfront than lithium-ion. They are robust, resilient and reliable. Lead-acid batteries can be discharged up to 80 percent of total capacity without any repercussions.

One major downfall of the lead-acid solar battery is that its power capacity drops significantly in colder temperatures. Additionally, they are big, bulky and difficult to maintain.

Lead-acid solar batteries are recycled much more frequently than lithium-ion batteries – usually into new batteries, boosting their case for environmental friendliness. However, they require a lot more materials to produce than lithium-ion batteries do, meaning more mining, and a bigger environmental impact.

Lithium-Ion Batteries

Lithium-ion batteries are built on much newer technology and are low maintenance. Their biggest advantage is their significantly improved lifespan, with faster charge and discharge times across their capacities.

They have an improved depth of discharge * and lose less capacity to irregular discharging. They are light, compact, easy to install and easier to dispose of.

They perform well both in colder and hotter temperatures. But they cost much more upfront than lead-acid. The longer lifecycle of this battery means that despite a higher initial investment, the battery may well cost less over its lifecycle.

Lithium-ion batteries can also charge much faster at higher voltages. While it can take lead-acid batteries up to 16 hours to fully charge, even the slowest charging lithium-ion batteries can fully charge within about four hours.

* A battery’s depth of discharge (DoD) indicates the percentage of the battery that has been discharged relative to the overall capacity of the battery.

We market the full range of Specialized Solar Solution (SSS) ES battery storage as well as the following Battery Storage products:

Victron Gel (whole series)

The GEL model range offers best deep cycle durability and overall longer life. The use of high purity materials and lead calcium grids ensure that for both AGM and GEL products have particularly low self-discharge so that they will not go flat during long periods without charge.

Freedom Won (whole series)

Freedom Won provides competitive prices made possible by bulk imports as well as comprehensive technical backup and design assistance. Freedom Won has also now extended the battery warranty in most applications to 5 years spurred by our confidence gained from our own test programme in electric vehicles, which is far more demanding on the batteries than stationary power systems.

Solar MD

Solar MD specializes in Lithium-Ion battery storage for residential, commercial and utility scale applications. Solar MD designs the intelligent battery management system inhouse. This design allows cell level monitoring, protection and control. Major Inverter brands are compatible with Solar MD systems. Our solutions are compatible with low voltage as well as high voltage power conversion systems.

Redflow – Zinc0bromide batteries

Featuring a plug-and-play storage system and the ability to self-manage, protect and monitor 24/7, our range of zinc-bromide flow batteries can shift energy in large volumes. The batteries are designed to support applications ranging from telecommunications and renewables integration to on-grid and off grid remote power, microgrids and smart grids, and transmission and distribution deferral.


As the world’s leading manufacturer of deep-cycle flooded, AGM and gel battery technology, Trojan Battery Company is committed to providing clean and reliable energy storage that enhance the way people live and work around the world. For more than 90 years, Trojan Battery has focused on manufacturing the highest quality, deep-cycle batteries available in the industry


Forbatt Lead-Acid Batteries have been on the South African market for over 23 years. The market share has grown in leaps and bounds, making it one of the top choices for professionals, installers, specialists and end users. The key to our growth has been the reliability of our batteries across the range. Our build quality and longevity is amongst the best on the market – just ask the professionals that use Forbatt Lead Acid Batteries.