But with so many options available, it is easy to get lost. That is why, in this article, we explain in a simple and practical way how to choose a solar battery and what aspects you should take into account to avoid making a mistake.

Power, Capacity and Inverter Compatibility: What You Need to Know

When looking for a solar self-consumption battery, it is important to pay attention to three key factors: power, capacity, and compatibility with your inverter.

1. Power: How Much Energy Can You Use at the Same Time?

Power indicates how much electricity the battery can deliver at a given moment. If you switch on several appliances at home at the same time (such as the oven, air conditioning, or an electric car charger), you will need a battery with enough power to avoid outages or limitations.

2. Capacity: How Much Energy Can You Store?

It is measured in kilowatt-hours (kWh) and tells you how much energy you can store in the battery. The higher it is, the more electricity you will have available when there is no sunlight. To determine what capacity you need, consider:

• How much energy you consume daily.
• Whether you use more electricity at night.
• How much independence from the electricity grid you want.

A good recommendation is not to go overboard or fall short. Oversized batteries are more expensive and may be underused, while smaller ones empty quickly and may wear out sooner.

3. Inverter Compatibility: Making Sure They Work Well Together

The inverter is the device that converts solar energy into usable electricity for your home. Not all batteries can be connected to just any inverter. That is why it is essential to choose a battery that is compatible with your inverter, so that the system works safely and efficiently.

Make sure that:

• The model is approved by the inverter manufacturer.
• It uses standard communication protocols (such as CAN or RS485).
• It offers direct or plug-and-play integration with your equipment.

Advantages of Choosing Modular and Scalable Batteries

Nowadays, many individuals and businesses opt for modular and scalable batteries, as they offer greater flexibility and adapt to each user’s real needs.

What Does It Mean for a Battery to Be Modular?

It means that it is made up of several independent modules. You can start with a small capacity and add more modules when you need more energy, without having to change the entire installation.

And Why Is It a Good Idea?

• Total flexibility: If you install more panels in the future, buy an electric car or your consumption increases, you can easily expand the battery.
• Easy maintenance: If one module fails, you do not need to replace the entire battery — just that block.
• Long-term savings: You do not have to make a large initial investment. You can expand gradually, according to your needs.
• Better use of space: They adapt to different types of homes or businesses, even when space is limited.

Ultimately, if you are considering a solar self-consumption battery, going modular is a safe bet for the present… and also for the future.

Tips for an Efficient and Safe Installation

A good choice does not end with buying the battery. It is just as important that the installation is carried out properly, following minimum standards of quality, safety and efficiency.

Here are some practical tips:

• Install in a suitable location: The battery should be placed in a protected, well-ventilated area, free from moisture or extreme temperatures. Avoid exposing it directly to sunlight or severe cold.
• Make sure it has a BMS: The Battery Management System (BMS) controls charging, protects against overcharging, and extends the lifespan of the equipment.
• Trust professionals: Look for certified and experienced installers. In addition to ensuring safety, they will help you comply with electrical regulations.
• Monitor your consumption: Some batteries allow you to see on your mobile how much energy you are generating, storing, and consuming. This helps you optimise your usage and detect potential issues.

Choosing the right battery for your solar self-consumption system does not have to be complicated. You just need to be clear about your consumption habits, have compatible equipment, and go for a solution that you can adapt over time.

A good solar self-consumption battery will give you energy freedom, reduce your electricity bill, and contribute to a more sustainable model. And if it is also modular, safe, and compatible with your inverter, you will be making a smart long-term investment.

Are you ready to take the next step towards energy self-sufficiency?

What Is Curtailment?

Curtailment is an order from the electricity system operator —in Spain, Red Eléctrica de España (REE)— to partially or completely stop the generation of renewable energy, even when technical and environmental conditions are favorable. This phenomenon can be caused by two main factors:

• Grid congestion, that is, the infrastructure cannot transport all the energy generated.
  
• Excess supply compared to reduced demand, which can lead to zero or even negative prices.
  

This type of interruption, also known as curtailments, especially affects large-scale solar and wind installations, as well as certain industrial self-consumption systems.

What is the duck curve and why is it related to curtailment?

The term PV duck curve originated in California (CAISO, 2013) and graphically represents the imbalance between solar generation – which peaks at midday – and electricity demand – which increases in the evening. The result is a duck-shaped curve: low demand during solar hours and a sharp increase in the afternoon, when solar output drops.

This mismatch generates overproduction during the day which, if it cannot be stored or transported, inevitably leads to curtailment. In countries like Spain, with high solar irradiation rates and strong photovoltaic penetration, this curve becomes more pronounced during weekends or holidays, when demand is lower.

What is photovoltaic pricing (apuntamiento fotovoltaico) and how is it affected?

Photovoltaic Pricing refers to the ratio between the average electricity market price and the average price at which solar energy is sold during a specific period. When the grid is saturated and there is excess solar generation, the electricity price drops. As a result, the apuntamiento also decreases, reducing income for solar producers.

Low solar pricing is especially problematic when there are no storage systems in place, as it prevents capitalising on the most profitable hours. Without batteries, the energy produced at midday must be fed into the grid at minimal or even zero prices.

Main Causes of Curtailment in Spain

• Grid saturation: many plants are located far from the consumption point and are connected to insufficient infrastructure.
  
• Lack of distributed storage: without batteries, it is not possible to store surplus solar energy.
  
• Low-demand hours: weekends, holidays, or vacation periods.
  
• Delays in regulatory planning: lack of coordination between new renewable generation and evacuation capacity.

Consequences of Curtailment for Producers and Investors

• Direct economic losses: unsold energy represents a drop in return on investment (ROI).
  
• Impact on PPA contracts: in power purchase agreements, curtailment can lead to disputes or penalty clauses.
  
• Reduction of the performance ratio: technical indicators of the plants deteriorate.
  
• Investor uncertainty: reduces the attractiveness of the sector without clear policies supporting storage.

Technical Solutions to Curtailment

The main solutions involve providing the electrical system with greater flexibility:

• Energy storage (BESS): allows absorption of solar surplus and dispatch during peak demand hours.
  
• Digitalisation and forecasting: AI-based systems to anticipate grid congestion or price drops.
  
• Participation in flexibility markets: buying/selling in intraday markets or ancillary services.
  
• Smart demand management: adapting industrial consumption to hours of maximum solar generation.

What Role Do Batteries Play in Combating Curtailment?

Industrial batteries and self-consumption installations with storage are key to mitigating curtailment. They allow:

• Postpone solar feed-in to periods of higher prices.
  
• Maximise photovoltaic pricing (apuntamiento) and revenue per kWh generated.
  
• Avoid economic losses due to forced curtailment.
  
• Participate in new business models, such as energy communities or demand aggregators.

In addition, in industrial systems, batteries help improve power quality, reduce peak demand, and enhance system stability.

In addition, in industrial systems, batteries help improve power quality, reduce peak demand, and enhance system stability.

According to recent data, more than 110 GWh of renewable energy was curtailed in Spain in the first quarter of 2023 alone, mostly wind power. This phenomenon is expected to continue growing if structural solutions are not implemented.

New European regulations—such as Regulation EU 2023/1542—already include measures to promote battery storage, repairability, and eco-design. The mandatory inclusion of storage systems in new renewable energy parks is also being promoted.

Conclusion: towards a renewable system without waste

Curtailment is the direct consequence of partial success: we have installed a lot of renewable generation, but without the necessary infrastructure to take full advantage of it. If we want a clean, stable, and profitable system, we must integrate technologies such as energy storage and a smart grid that efficiently connects generation and consumption.

The solution is not to halt renewable growth, but to make it smarter and more resilient. And along that path, batteries and digitalization play a leading role.

What to consider when buying a solar home battery

Before choosing a battery for your self-consumption installation, it is important to be clear about several key criteria:

Chemical technology

Lithium-ion batteries – especially those based on LiFePO₄ (lithium iron phosphate) technology – offer greater safety, longer service life and a better useful discharge rate than other technologies such as lead-acid. At IONLY we rely exclusively on LiFePO₄ for its advantages in efficiency, thermal safety and sustainability.

2. Usable capacity and scalability

It is important that the battery is sized according to your consumption and generation habits. But just as important is that it can be easily scaled if your needs change. Our solutions are modular, so you can start with a minimum capacity and expand in the future without changing the entire system.

3. Compatibility and integration

A good battery must be compatible with your inverter and your energy management system (EMS). IONLY solutions are open and easily integrated, compatible with the main inverters on the market.

4. Real life cycles

Don’t just go by the theoretical figures. Ask how many real cycles the battery offers and under what conditions. Our batteries are designed for more than 6,000 real cycles at 80% DoD, with a slow and stable degradation curve.

5. After-sales service and warranty

Who will give you support if there is a problem? Where are the batteries manufactured? Does the company have traceability of each module? In IONLY we give real warranty from Europe, with direct technical support from the manufacturer.

Advantages of batteries “Made in Europe” versus “Made in China”.

The market is saturated with inexpensive imported batteries, but there are key differences you should be aware of:

• Manufacturing quality and control: European batteries, such as IONLY’s, are assembled under the highest quality standards, with full traceability of each cell and each BMS.
  
• Local technical support: If you buy from a distributor that imports Asian products, the support will depend on the intermediary. We provide direct support from the manufacturer, without intermediaries.
  
• Regulatory compliance: Europe is raising the regulatory bar with regulations such as EU 2023/1542, which requires sustainability, traceability, reparability and a digital battery passport. At IONLY, we are ahead of the regulation with products 100% designed for the European framework.
  
• Carbon footprint and sustainability: A battery manufactured and distributed locally has less environmental impact than one transported from Asia. In addition, IONLY is committed to eco-design and repairability to extend the life cycle of each system.
  

Why IONLY?

At IONLY we don’t sell batteries, we manufacture smart storage solutions designed to last. We focus exclusively on lithium-ion batteries for solar storage because we believe in energy independence as a driver of change.

• We design modular, scalable and repairable batteries.
  
• We assemble in Europe under technical and ethical standards.
  
• We are committed to transparency: every technical specification is justified, every component is traced.
  
• We accompany installers and professionals with clear documentation, agile support and training.
  
• We do not compete with our customers: we do not sell to the end user. We are a brand 100% oriented to the professional channel.
  

Are you considering adding solar storage to your self-consumption system? Are you looking for a reliable, compatible battery that is ready for future European regulations? Let’s talk. At IONLY we are here to help you.

At IONLY, we specialize in manufacturing modular and sustainable batteries based on LiFePO₄ (lithium-ferrophosphate) technology, specifically designed for stationary solar storage.
Join us to understand how its lifetime is measured, what factors affect it and why this technology is one of the most reliable on the market.

What does “charge cycle” mean and how does it influence battery life?

A charge cycle is the complete process of charging and discharging a battery. For example, if you use 50% of the battery today and the other 50% tomorrow, that counts as a complete cycle.

The service life of a solar LiFePO₄₄ solar battery is measured in cycles, not in years directly. The more cycles a battery can withstand without losing useful capacity, the longer it will last. And this is where LiFePO₄ batteries shine:

• A quality LiFePO₄ solar battery such as those from IONLY can achieve more than 6,000 cycles at 80 % discharge.
• Translated into years, this can mean 15 years or more of operation under normal conditions.

This makes LiFePO₄ technology one of the longest-lived technologies available today for solar storage.

Factors affecting the lifetime of a solar battery

Although technology is key, the actual duration of a LiFePO₄ solar battery also depends on how it is used and the environment where it operates. Some important factors:

• Depth of discharge (DoD): The deeper the usual discharge, the more the battery is strained. It is therefore recommended not to always discharge 100%.
• Temperature: Constant high temperatures can accelerate aging. At IONLY, we design enclosures and systems that guarantee optimal ventilation.
• BMS quality: The Battery Management System ( BMS ) is crucial for balancing cells, avoiding overcharging and extending service life. At IONLY we use high performance industrial BMS.
• Frequency of use: using the battery every day is not a problem with a LiFePO₄, but it requires good charge/discharge management to maximize its life.
• Proper charging: Using compatible and well-calibrated chargers prevents premature damage.

In short: a well-dimensioned and well-managed LiFePO₄ solar battery can last more than a decade with total reliability.

LiFePO₄ vs other technologies: which one lasts longer?

Compared to other common storage technologies, lithium-ferrophosphate has clear advantages:

As you can see, LiFePO₄ technology not only offers more cycles, but also greater safety, stability and a lower long-term cost of ownership. That’s why we at IONLY focus exclusively on this technology for all our solar storage systems.

Investing in durability and peace of mind

When choosing a solar storage batteryyou’re not just buying energy: you’re investing in stability, savings and long-term autonomy. With LiFePO₄ technology and intelligent management, you can forget about constant maintenance and premature replacements.

At IONLY, we design and manufacture systems that not only work, but are built to last. And if you have doubts about how to size your system or which battery is best suited to your solar installation, we will help you configure it without obligation.

Here’s why LiFePO₄ batteries are changing the rules of the game in solar energy storage.

Characteristics and advantages of LiFePO4 technology over other technologies

Although there are different types of lithium batteries, LiFePO₄ technology stands out for several reasons:

1. Longer life: These batteries can be charged and discharged thousands of times without losing capacity, which means they last longer than other alternatives.
2. Very safe: They are chemically stable, which reduces the risk of overheating or accidents. They do not require complex cooling systems.
3. High efficiency: They make better use of the energy they receive. Less losses, more yield.
4. More sustainable: They do not contain cobalt or nickel, which are scarce and problematic materials from an environmental and ethical point of view.
5. Consistent performance: They maintain stable power delivery, making them ideal for solar installations that require reliability.
   

Most common applications of LiFePO₄ batteries.

At IONLY, we design modular batteries that adapt to different needs within solar storage. Some common applications are:

• Self-consumption in homes: To store the solar energy generated during the day and use it at night.
• Companies and industries: To reduce electricity costs, avoid blackouts or stabilize the internal network.
• Energy communities and microgrids: Where energy is shared among several users at a local level.
• Off-grid areas: Perfect for rural houses, shelters or isolated installations that rely exclusively on solar energy.
  

Why LiFePO4 batteries are the safest and longest-lasting choice

LiFePO₄ batteries offer a combination that is hard to beat: long life, stability and minimal maintenance.

• Very low fire risk: Its chemistry is naturally safe, even under demanding conditions.
• They work well with heat and cold: They do not require special conditions to operate.
• They do not degrade easily: They maintain good capacity over time.
• Almost maintenance-free: They operate automatically thanks to their electronic control system.

At IONLY, we not only manufacture these batteries: we adapt them to integrate perfectly with solar systems, complying with European regulations (such as the EU2023/1542 Directive) and focusing on sustainability and reparability as key values.

Cost analysis in Europe

1. Regions with cheap electricity and cheap labor:
   Countries such as Portugal and Serbia stand out as the cheapest options. The combination of low prices for both electricity and wages positions these regions as strong candidates for prismatic LFP cell production. In addition, their lower living costs favor more affordable infrastructure investment.
2. Countries with expensive electricity and cheap labor:
   The United Kingdom is an interesting example: although electricity prices are high, labor costs lower than the European average allow keeping production costs slightly below average. However, economic uncertainty after Brexit and export costs could be factors to consider.
3. Cheap electricity, but expensive labor:
   In countries such as Sweden and Finland, although electricity is relatively inexpensive, high wages offset that advantage, resulting in higher production costs. These regions are less competitive unless automation is widely used to reduce reliance on labor.
4. Regions with high costs in both factors:
   Germany, with high prices for both electricity and labor, has the highest production costs in Europe. However, Germany has key competitive advantages, such as its highly skilled talent and advanced manufacturing expertise. This can result in better yields and higher levels of automation, partially mitigating the high upfront costs. In addition, government support in the form of energy subsidies and incentive programs can make production in the country more viable.

Additional factors to consider

In addition to direct costs, other factors play a crucial role in the selection of a location for a gigafactory:

• Availability of talent: Countries such as Germany and Sweden have a skilled workforce in related sectors, which facilitates the training and hiring of specialized personnel.
• Government support: Subsidy policies, tax incentives and access to renewable energy can significantly alter costs. Regions with favorable policies, such as some Eastern European countries, are increasingly attractive to investors.
• Proximity to electric vehicle assembly plants: Many gigafactories are strategically located near electric vehicle production centers to reduce transportation costs and improve logistics.

What is the best option for a gigafactory?

In terms of initial costs, Portugal and Serbia are outstanding options, especially for manufacturers looking to minimize operational investment. However, countries such as Germany, although more expensive, offer long-term advantages in terms of quality, efficiency and access to talent, especially if the plant is committed to high levels of automation and optimization.

As demand for electric vehicle batteries continues to grow in Europe, countries that manage to balance cost, infrastructure and government support will be the preferred destinations for new investments in gigafactories.

Falling prices: what is driving this trend?

1. Technological innovations:
   Improvements in battery design are achieving increases in energy density of up to 30%, which means they can store more energy in a smaller space. Technologies such as cell-to-pack design, which eliminates intermediate modules and optimizes space, are reducing costs and improving performance.
2. Falling prices of green metals:
   Metals such as lithium and cobalt, which account for almost 60% of the cost of batteries, have experienced a significant drop in prices following the peak between 2020 and 2023. This decline has been key to making batteries cheaper, contributing to more than 40% of the projected cost reduction.

Price projection

In 2022, the global average battery price was $153 per kWh, dropping to $149 in 2023. By the end of 2024, this cost is expected to reach $111 per kWh, with a projected decline to $80 per kWh in 2026. This level will allow electric vehicles to reach parity in total cost of ownership with internal combustion vehicles, even without subsidies.

Dominant battery types

Currently, the market is led by two types of lithium batteries:

• Nickel-based batteries: They represent 60% of the market due to their high energy density.
• LFP (lithium iron phosphate) batteries: They capture between 35% and 40% of the market, standing out for their durability, lower cost and less dependence on expensive materials such as cobalt.

Although emerging technologies such as solid-state batteries promise to revolutionize the industry with higher energy density and increased safety, their mass adoption is still years away due to challenges in large-scale production.

Impact on battery manufacturers

The battery industry has significant barriers to entry. Established manufacturers, which control 80% of the market, have stepped up their investment in research and development, making it difficult for new companies to compete. For new entrants, reaching the necessary scale of production and achieving cost efficiencies can take more than a decade.

What does this mean for consumers?

Falling battery prices will have a direct impact on the final price of EVs. According to Goldman Sachs, by 2026, consumers will be able to buy an EV at the same total ownership price as a gasoline car, even considering the faster depreciation of EVs due to constant technological improvements.

This change will not only make EVs more affordable, but will also contribute to massive consumer-driven adoption, especially in markets such as the United States, where fuel costs and environmental regulations will play a key role.

Why battery-powered trains?

Trains in the UK currently run on electric power supplied by overhead lines or with on-board diesel generators on non-electrified tracks. The latter option has for decades been the standard solution for network sections not connected to electrification. However, maintenance and expansion of electric cable infrastructure is costly, leaving large portions of the rail system with limited sustainable options.

Battery-powered trains are emerging as a cost-effective hybrid solution to this challenge. For example, Hitachi has developed a “tri-mode” train that combines battery power, overhead line electricity and diesel generators, enabling fuel consumption to be reduced by up to 50% on routes without electrification.

Technology behind battery-powered trains

Today’s battery-equipped trains use technology similar to that of electric vehicles (EVs). Hitachi’s test model replaces one of the diesel generators with a set of 16 lithium batteries, which can be recharged while the train is operating on electrified tracks or in stations in 10 to 15 minutes.

These trains have the ability to automatically switch between different energy sources, maximizing efficiency. In addition, it has been proven that existing electric trains can be retrofitted with batteries to make them more sustainable, reducing the need to replace entire fleets.

What makes them viable now?

Although battery-powered trains are not a new concept, recent advances have made them a practical alternative. The first lithium battery-powered trains entered service in Japan in 2016, but interest in the UK has grown thanks to improved battery capacity and government support towards greener transport.

For example, the UK government aims to achieve net zero carbon dioxide emissions by 2050. In this context, the transition to all-electric or hybrid trains is a natural step.

Even so, limitations remain. Currently, batteries do not have the range to cover all routes without electrification. For example, Hitachi’s test train can run 70 km on batteries, sufficient for routes between London and Oxford, but insufficient for others such as Crewe-Holyhead.

Are battery-powered trains safe?

Safety is a priority in the development of this technology, especially considering the risks associated with lithium batteries. Although these batteries are very safe when handled correctly, they can experience a phenomenon called thermal runaway in the event of severe damage, which can lead to fires that are difficult to control.

However, tests conducted by Hitachi have shown that these batteries are highly resistant. To ensure passenger safety, measures have been implemented such as:

• Heat shields to prevent a fire in one cell from affecting other cells.
• Cooling systems to maintain an optimum temperature in the batteries.
• Advanced software that monitors and regulates cell operation.

In addition, the trains are designed so that damaged units can be safely evacuated and removed from the tracks without compromising the integrity of the passengers.

The future of rail transport

Although battery-powered trains still face technical and economic challenges, they represent a key transition to a more sustainable rail network. Hybrid solutions, such as tri-mode trains, are intermediate steps towards full electrification, while battery technology continues to improve in terms of capacity and weight.

With companies like Hitachi and Siemens leading the way, the rail industry is at a tipping point that promises not only to reduce environmental impact, but also to modernize existing infrastructure at more manageable costs.