Carbon Foam Batteries for Solar PV Systems

Solar PV systems rely on batteries for energy storage. There’re several types of energy storage systems you can use for your solar PV systems, each of which has its own strengths and weaknesses.

To choose the best solar power storage solution, though, you need to understand exactly what your target battery is capable of on both ends.

This article covers everything you need to know about carbon foam batteries, including their working principle, characteristics, pros and cons, and an analysis of their suitability for solar PV systems.

Let’s get started.

What is a Carbon Foam Battery?

For a better understanding of these batteries, let's get to know what foam batteries are first.

Foam batteries are batteries where the electrodes are electroplated on foam as the primary raw material.

Foam is a highly porous material with excellent surface area to volume ratio properties. When a web of carbon atoms is structured together into a single unit, they form carbon foam– a superb material that can be used to fabricate batteries.

Carbon foam makes an excellent battery material as it exhibits the following characteristics:

  • High surface area to volume ratio
  • Wide operating temperature
  • Exceptional thermal stability
  • Great formability
  • Lightweight

Pushed by the need to find an alternative for the highly corroded lead-acid batteries, Dr. Rajeev of the CSIR-Advanced Material Processes Research Institute, Bhopal, and his whole team of researchers developed carbon foam batteries.

The very first carbon foam batteries they made had a density less than 0.3g/cc and were 85% porous.

Carbon Foam Batteries: The Design

The design of carbon foam batteries is quite straightforward. The anode of these batteries is typically carbon, while the cathode is nickel oxyhydroxide.

The most unique feature of carbon foam batteries is how the microcells are arranged in a 3-D structure.

These microcells have a high surface area to volume ratio, so they can store and deliver more energy, plus have an increased cycle life and charge/discharge characteristics.

These are no doubt the features you’d want for your solar PV energy storage systems.

How do Carbon Foam Batteries Work?

Carbon foam batteries have a unique working principle – they are half capacitors, half batteries.

A capacitor stores power without requiring chemical components and has excellent charge-discharge characteristics.

In contrast, chemical components (electrodes and electrolytes) are used in batteries to store power. These provide excellent energy storage capabilities.

Carbon foam batteries capture energy in their ‘battery’ section, which is made up of nickel oxyhydroxide cathode and carbon anode.

Impressively the negative plate is resistant to sulfation, a characteristic that improves the energy storage efficiency significantly.

The carbon foam 3D structure, which is the primary raw material in carbon foam batteries, provides the cathode with a large area in which to embed and store energy.

Once the energy has been produced via chemical reactions, it's stored in the form of electrolyte ions (capacitor section).

Please note: Due to their sulfation resistance feature, carbon foam batteries will typically not charge to full capacity.

Carbon Foam Batteries: Characteristics/ PV Suitability Analysis

Charging characteristics

Carbon foam batteries have stellar charging characteristics due to the microspores/microcell design of the carbon foam material.

The charging of carbon foam batteries is smooth even at low temperatures, although this is insignificant for solar storage systems that store power when the temperatures are high.

Please note: Due to their sulfation resistance feature, carbon foam batteries will typically not charge to full capacity.

Deep charging capabilities

Carbon foam batteries can accept deep charging for long while still maintaining their optimum performance.

In a solar PV situation, this means that you have a reliable energy storage system you can use when solar power production is at its peak.

Battery efficiency

Carbon foam batteries have carbon foam porous foam with microcells arranged in a 3-D structure.

Also, the small separator reservoir in carbon foam batteries is redistributed to the micropores raising the efficiency of these batteries significantly.

The throughput efficiency of carbon foam batteries is 90% or more.

Size and weight

A 12V, 116Ah battery measures 13.6″ × 6.7″ × 9.4″ while a 4V 450 Ah battery measures 10.5″ × 6.9″ × 17.2″. With such small sizes, the batteries become more efficient, and they won't take up much room in your storage space.

In terms of weight, carbon foam batteries are superbly lightweight, hence are the best energy storage system you can have for off-grid applications.

Depth of discharge

You can do 80-100% discharge without damaging the long-run performance of carbon foam batteries.

This means that you can get double power with carbon foam batteries than you would with other batteries such as lead-acid or lithium-ion simply because of the relatively higher depth of discharge.

Self-discharge rate

Carbon foam batteries have a low self-discharge rate, so you can be sure they’ll keep the stored power when they’re not put into use. And the good thing is, they can maintain power even when they’re left in a partial state of charge.

Aside from their low self-discharge characteristics, carbon foam batteries can easily recover from a long period of being discharged to their original state.

Please note: It’s not recommended to keep your batteries idle for a long time since they’ll eventually degrade.

Excellent thermal characteristics

Unlike lithium batteries, carbon foam batteries have no thermal runaway issues and are not likely to cause fire or explosion accidents.

The optimum operating temperature range of carbon foam batteries is -4°F to 122°F (-20°C to 50°C).

Corrosion resistance

Carbon foam batteries experience less localized corrosion and wear out on the positive electrode.

For renewable energy applications where a long-lasting power storage solution is desired, you'd want a battery that resists corrosion like carbon foam.

Sulfation resistance

Sulfation is a major performance killer for AGM batteries.

Impressively, carbon foam batteries are highly resistant to sulfation, meaning they’re able to maintain their capacity for an extended period.

Carbon foam battery price

The cost of carbon foam is around 60% of most battery materials’ cost which means low production cost for carbon foam batteries.

A 4V, 450Ah firefly carbon foam battery will cost you around $750.

Cycle life

One of the most impressive features of carbon foam batteries is their extended cycle life.

A typical carbon foam battery will do at least 5000 cycles. This can get higher with proper care and charging habits.


Compared to conventional batteries for solar such as lead-acid, carbon foam batteries are 2-3 times more long-lasting.

Typically, you’ll get an average of 10 years of useful life from carbon foam batteries.

Material availability

Carbon foam is a readily available material since it can easily be made anywhere globally. This makes carbon foam batteries perfect for remote areas that rely entirely on solar power.

Brands/ Manufacturers

Some major companies currently making carbon foam batteries are Ocean planet Energy, Total Battery, Bosch, and Varta.

One of the most commonly used carbon foam batteries is by Ocean planet Energy- the firefly carbon foam battery. These batteries have revolutionized the battery industry and are no doubt a game-changing technology.

Environmental concerns

As the world becomes more concerned with increasing pollution from conventional power-producing activities, there has been a push to adopt renewable energy sources.

The great potential that lies in renewable energy like solar can only be realized if green and highly effective batteries such as carbon foam batteries are formulated.

Carbon foam is non-toxic, not to mention that carbon foam batteries are completely sealed, so they pose no environmental pollution problems.


Carbon foam batteries can be recycled in the same way as leading acid batteries. With a developed recycling technology already in place, you have peace of mind knowing you can safely recycle the batteries at the end of their useful life.

Advantages of Carbon Foam Batteries

More applications for solar power

Carbon foam batteries are light, cheap, and safe to use. These characteristics make them suitable for a wide range of applications.

Carbon foam batteries will sort you out whether you need a backup battery for stationary solar power uses or a portable energy storage solution for off-grid activities.

A reliable energy storage system for solar PV

Thanks to their high energy density, carbon foam batteries can be charged and discharged effortlessly.

In a solar PV situation, this is crucial as you need to capture electricity as it gets produced since the intensity and duration of the sun are always unpredictable.

High cycle life and long-lasting batteries

The long service life of carbon foam batteries keeps them ahead of most conventional energy storage systems for solar power.

Since solar energy is always a long-term investment, you want an energy storage solution that stands the test of time, so that you can be sure you'll recoup your investment. Luckily, carbon foam batteries check the box of longevity.

Cheaper than other technologies

Carbon foam is a widely available material with pretty established processing technology.

The same applies to carbon foam batteries that are now readily available worldwide. As mentioned earlier, you should expect to spend around $700 for a standard-sized carbon foam battery.

Disadvantages of Carbon Foam Batteries

Poor charging can degrade the battery

Although carbon foam batteries will tolerate intense charging occasionally they can degrade with continued poor charging. Poor charging is like when the current is extremely high or is delivered in a surging manner.

If you still want your carbon foam batteries to hit their expected lifespan, you should charge them properly.

Higher operational costs

Despite the low manufacturing cost of carbon foam batteries, it can be costly to run them due to the additional components needed.

For example, an onboarding charging system may be needed to convert AC to DC and protect the battery from current surges.

Since such as component improves the longevity of your carbon foam batteries, you may have to spend additional costs for it.

Limited size options

The carbon foam battery industry is still evolving, and currently, only a few size options are available.

If, for instance, you're to go with the firefly carbon foam AGM batteries mentioned earlier, you'll only have two size options.

This means that you're forced to buy several of these batteries to build a considerable battery unit.

Frequently Asked Questions

Is investing in carbon foam batteries worth it?

Carbon foam is revolutionizing solar energy storage systems and is currently regarded as one of the brilliant options to invest in.

While there’re maybe other great power storage options for your solar PV system, carbon foam batteries promise better performance, enhanced energy efficiency, and extended cycle life.

Do carbon foam batteries require maintenance?

Like any other AGM batteries, carbon foam batteries are sealed, so they don’t require maintenance.

This doesn’t mean that you should neglect them entirely. Keeping them in a stress-free spot and using them occasionally would help keep their pristine conditions for longer.

Impressively, these batteries don’t need to be topped off no matter how intense you go discharging them.

Are carbon foam batteries AGM batteries?

Carbon foam batteries are Absorbent Glass Mat (AGM) batteries with superior power and charge characteristics.

Essentially, carbon foam as a battery material removes all the limitations of AGM batteries and hence the popularity in solar PV applications.

In fact, carbon foam AGM batteries would be a better term to describe these batteries.

Who are carbon foam batteries for?

Carbon foam batteries are for anyone looking for a durable solar storage system with good charge and discharge characteristics.

There's a lot that appeals about carbon foam batteries, but these two characteristics stand out as they've been the prevalent problems for lead-acid and AGM batteries.


Carbon foam batteries are lightweight, relatively cheap, and long-lasting energy storage systems. These characteristics make these batteries highly suitable for solar PV applications.

Carbon foam batteries have high running costs and limited size options, which is obvious as their major drawbacks.

Each renewable energy battery has its own shortcomings, so these are things you’ll just have to bear with if you choose these batteries.

All in all, carbon foam batteries have the best in class performance, and you can never go wrong investing your money in them.