Solar Battery: Everything You Need to Know About Storing Photovoltaic Energy at Home

Solar energy is increasingly convincing private households looking to reduce their electricity bills and become more independent. One solution for optimizing your photovoltaic system is the solar battery, an energy storage system that allows you to store generated electricity for later use. Also known as a photovoltaic storage unit or home storage system, this system offers the ability to consume your own green electricity even when the sun isn't shining. Whether you are a homeowner looking to optimize your self-consumption (or a business aiming to secure your power supply) – this informal and informative guide answers frequently asked questions about solar batteries, how they work, installation, and selection.

What is a solar battery and what is its purpose?

A solar battery is a storage system that collects electricity generated by solar modules for later discharge. Specifically, it serves to store excess photovoltaic energy produced during the day (when the sun is highest and production exceeds your momentary demand) for reuse in the evening or at night when the modules are no longer supplying power. Without a battery, unused solar power is either lost or fed into the public grid. With a storage system, this free electricity is no longer wasted: It is stored locally and powers your home when your modules are insufficient.

In short, the solar battery aims to increase your self-consumption rate (to consume a larger portion of the solar power you generate yourself) and can also function as an emergency power solution. In the event of a grid outage, a correctly sized battery can take over the supply and power your essential devices for several hours or even longer, depending on its capacity.

How does photovoltaic energy storage work?

For better understanding: A solar module converts solar radiation into direct current (DC). This DC can either be converted into alternating current (AC) by an inverter to directly power your devices, or it can be stored directly in a battery. The functionality of a solar battery can be summarized as follows:

1. Charging: When the modules produce more electricity than the house consumes in real-time, the excess DC is directed to the battery. A control device (solar charge controller or hybrid inverter) manages this charging process to prevent damage to the battery.

2. Storage: Energy is chemically stored in the battery (in electrochemical form, like a giant battery). Storage capacity is expressed in kilowatt-hours (kWh) and indicates how much energy the battery can store.

3. Discharging: When solar production becomes insufficient (evening, night, cloudy days) or in the event of a grid outage, the battery sends the stored electricity to an inverter (or uses an integrated inverter) to convert it into usable AC for your household appliances. The house then draws from the battery to meet its needs until it is depleted or the sun shines again.

It is important to note that a battery storage system requires a compatible inverter. In standalone systems (off-grid island systems), a charge controller and an off-grid inverter are used to manage the battery. In grid-connected systems with storage, a hybrid inverter is typically used, which can simultaneously control PV production, battery charging/discharging, and exchange with the public grid. Some battery models even have an inverter directly integrated (referred to as AC-coupled or "all-in-one" batteries), which simplifies their addition to an existing system.

What are the benefits of a home solar battery?

Installing a photovoltaic storage system at home offers several remarkable advantages:

• Maximizing self-consumption: By storing excess energy during the day, you can use your solar power in the evening. This allows you to increase your self-consumption of locally generated renewable energy to up to 70-80% or more, compared to about 20-30% without a battery. The result: your electricity bills decrease accordingly in the long term.

• Securing power supply: In the event of a power outage, a battery provides emergency power. You can continue to operate essential appliances (refrigerator, lighting, Wi-Fi, etc.) for several hours. This is a real plus for household or small office continuity.

• Optimizing system sizing: With a storage unit, even a small solar system can cover most of the demand, as energy is used at the optimal time. For example, a balcony solar kit, coupled with a small battery, can achieve a much higher self-consumption rate than a kit without a battery. It is estimated that a plug-and-play system without storage consumes about 50% of the produced electricity itself, while with a battery, it can be up to 80%.

• Contributing to environmental protection: By storing solar energy, you reduce your dependence on the grid (which is often powered by fossil fuels). You fully utilize every green kWh produced, thereby reducing your carbon footprint.

• Utilizing variable tariffs: In some cases, a battery can be used to store electricity from the grid during off-peak hours (cheaper night tariff) and feed it back during peak hours. This is not the case for all systems, but certain configurations with a bidirectional inverter allow this and offer additional savings.

In summary, a solar battery strengthens your household's energy independence while providing comfort and peace of mind. Of course, this represents an initial investment, but its profitability improves with rising electricity costs and potential local incentives for self-consumption.

How to choose (and size) a solar battery to suit your needs?

Choosing the right solar battery is crucial to get the most out of your system. Several criteria need to be considered:

• Storage capacity (kWh): This is the main criterion. It must match your energy consumption and desired level of autonomy. Calculate your electricity consumption during the sunless period (e.g., from evening to morning) to estimate the required capacity. A family with a nocturnal demand of 5 kWh will benefit from a battery of at least 5 kWh to cover a typical night. If you aim for two days of autonomy in bad weather, double this capacity, and so on.

  Example: A typical refrigerator consumes between 0.5 and 1.4 kWh per day. A 5 kWh battery could therefore operate it autonomously for about 3 to 4 days (in practice, other devices also consume electricity, but this gives an order of magnitude).

• Output power (kW): Check the nominal power and the current that the battery (or its inverter) can continuously and at peak supply. This determines which devices you can operate simultaneously. For example, to power a 2000 W kettle, the inverter/battery must be able to deliver at least 2 kW at peak. Current household batteries often offer between 3 and 5 kW of nominal power, which covers most residential applications outside central electric heating.

• System voltage: Small solar systems (motorhomes, remote locations with low power) generally use 12V or 24V batteries. For a complete residential building, 48V systems are preferred (more efficient for large capacities). Make sure to choose a battery that is compatible with your system's inverter or charge controller (12V, 24V, 48V...). Plug-and-play solar kits for balconies, on the other hand, have micro-inverters that feed directly into 230V, and any associated batteries (e.g., Zendure SolarFlow Kit) store energy in AC via a dedicated module – a special case where the battery voltage is not managed by the user.

• Battery technology: Today, two large families dominate the market: lead-acid batteries (gel or AGM batteries) and lithium batteries.

  • Lead-AGM/Gel batteries are cheaper to buy, tolerate low temperatures well, and are maintenance-free (sealed). However, they are heavy and bulky, their recommended depth of discharge is limited (often 50%), and their lifespan is shorter (approx. 500 to 1200 cycles depending on the model).

  • Lithium-ion batteries (especially the lithium iron phosphate variant LiFePO4) are more expensive but offer a longer lifespan (up to 3000-5000 cycles, i.e., 10 years and more of lifespan), a greater usable depth of discharge (80-100% possible), higher energy density (more compact for the same capacity), and excellent charge/discharge efficiency. In use, lithium therefore quickly amortizes itself thanks to its performance and lifespan. For this reason, most new home storage installations are based on lithium.

• Brand and Compatibility: Prefer recognized brands and ensure that the chosen battery is compatible with your inverter/controller. Some batteries communicate with specific inverters (management protocols, etc.). If you opt for an all-in-one hybrid system, ensure that the battery, inverter, and modules form a coherent whole. When in doubt, complete kits or the advice of a professional (or the seller's technical support) can help you.

• Budget and Expandability: Set a budget and remember that storage is a long-term investment. Compare the price per usable kWh (taking into account depth of discharge and life cycles). If your budget is tight, you could also start with a smaller capacity that is expandable later. Many batteries are modular: it is possible to add more in parallel or add additional modules to increase capacity over time.

Example of a modular solar battery pack with a total capacity of ~14 kWh (four assembled lithium LiFePO4 modules). This type of solution offers great flexibility to adapt energy storage to the evolution of your needs.

By considering these criteria, you can determine which battery best suits your consumption profile. Do not hesitate to use online simulators or consult a specialist to refine the sizing of your storage solution. In the NYLYN Solar Shop, you will find a selection of the best solar batteries on the market (Pylontech, Victron, Zendure, etc.), known for their reliability. Each product sheet contains the main specifications (capacity, power, life cycles) to help you choose. You can browse our collection for energy storage to compare the available options and make an informed decision.

How to install and connect a home solar battery?

Installing a solar battery varies depending on the system type and your electrical knowledge. For a small plug-and-play solar kit, don't worry: everything is designed for ease of use. For example, a balcony kit with a micro-inverter and integrated AC battery can be connected without an electrician: The battery is connected to the micro-inverter or a control unit with a few cables, and the whole system is connected to a standard power outlet.

For a photovoltaic home system with a large-capacity battery, however, the following steps and advice should be followed:

• Location: Install the battery in a protected, dry, frost-free, and extreme heat-protected location. A utility room, garage, or ventilated basement are ideal. Avoid living areas for safety and comfort reasons (lead-acid batteries can emit slight gases during charging, and all batteries must be protected from children/pets, etc.). Also, ensure that the floor or mounting can support the weight if it is a heavy stationary battery.

• Electrical connection: Follow the wiring diagram provided by the manufacturer precisely. In general, the battery is connected either to a hybrid inverter (which connects the modules, battery, and home grid) or to a charge controller (in off-grid DC systems). Use cables with appropriate cross-sections and the necessary protective devices: fuses or DC circuit breakers on the battery, disconnectors, grounding of the metal casing if necessary, etc. ⚡ Safety tip: When connecting the battery, switch off all sources (modules and grid) and observe the polarity (+ red, – black) to avoid short circuits.

• Configuration and commissioning: Once the wiring is complete, configure the system via the inverter or controller: Enter the battery capacity, type (lead-acid, lithium), and charge/discharge thresholds according to the manufacturer's recommendations. Modern hybrid inverters have an interface (screen or app) to easily configure these parameters. After the final check of the connections, you can restore power and test correct operation: The modules must charge the battery (check the screen/LED to see if charging is taking place) and the battery must be able to supply the house in the evening.

• Engage a professional? If you are not familiar with electricity, it is recommended to engage a qualified electrician to install a battery in a residential system. Although it is not very complex for someone knowledgeable, there are important safety aspects (risk of electric shock from DC, fire hazard from poor tightening or short circuit, etc.). A professional ensures compliance with standards (in Germany, VDE 0100 may be relevant) and can also advise you on sizing and the optimal location.

In summary: Connecting a solar battery to a small kit is feasible for a skilled DIY enthusiast, while for a complete home system, in-depth knowledge or engaging a specialist is advisable. In any case, carefully observe the supplied manuals and do not neglect safety. Once correctly installed, the battery operates autonomously without requiring special attention.

(Note: If your system is connected to the grid, inquire about any registrations or instructions from your energy provider regarding the installation of a battery. In most cases of self-consumption without feed-in, no extensive formalities are required in Germany, but it is better to be informed.)

Can a solar battery be charged without sun?

This is a frequently asked question, especially during long cloudy periods or in winter: How do you charge your solar battery when there is no sun? By definition, the main charging source remains the photovoltaic module. However, there are options for alternative charging:

• Via the electricity grid: If your system is grid-connected (hybrid inverter), you can usually configure the battery to charge from the grid at certain times. For example, some users choose to charge their battery at night when electricity is cheaper (off-peak tariff) to use it during the day. This can also serve as emergency power: During several sunless days, your battery charges via the grid to remain available if needed (one then speaks more of an "emergency power battery" than of classic self-consumption).

• With a generator: In remote (off-grid) locations without grid connection, the classic emergency solution is a gasoline or diesel generator. It is entirely possible to charge your solar battery via a generator: Simply connect the generator to a suitable charger or to the AC input of your system. The generator then supplies power to charge the battery during prolonged absence of sun. This is, for example, a common practice in medium-sized autonomous solar systems, where a small generator serves as a backup on rainy days.

• Other energy sources: Technically, there is nothing to prevent a solar battery from being charged with another renewable source: domestic wind turbine, stream water turbine, etc., via the appropriate controllers. The idea is that the battery is just a storage unit: You can fill it with any source, as long as you have the electronic equipment to adapt that source to the battery.

In short, yes, a solar battery can also be charged without sun. This requires additional equipment (grid charger, grid connection, or generator) and a minimum of management to avoid overcharging the battery. But it's reassuring to know that your investment will not go unused even in a very gray winter: You can always rely on the battery if needed by charging it differently.

Maintenance, Care, and Lifespan of a Solar Battery

One of the advantages of modern solar batteries, especially lithium batteries, is their low maintenance requirements. Here's what you need to know to care for your storage system:

• Monitoring and Use: Most batteries today are equipped with an electronic management system called BMS (Battery Management System), which regulates charging/discharging processes and prevents use outside the limits. Via the inverter or a mobile app, you can monitor the battery's state of charge (%), the cycles performed, and the temperature. In normal operation, you don't have to do much, except occasionally keep an eye on these indicators. Just make sure that the battery does not remain fully discharged for long periods (systems usually prevent this by shutting down before deep discharge).

• Ongoing Maintenance: For open lead-acid batteries (rarely used in household solar systems today), the electrolyte level must be checked and distilled water may need to be topped up. However, most solar batteries sold are maintenance-free (AGM, gel, sealed lithium batteries). Just make sure to dust off the ventilation grilles of the housing if necessary and check that no corrosion forms on the terminals or clamps. An annual check of the connections (retightening the cable lugs after the battery has been isolated, if necessary) is a plus for longevity.

• How long does a solar battery last? The lifespan depends on the technology and usage. A lead-acid battery typically loses 20% of its capacity after 300 to 500 cycles at 50% discharge and can last a maximum of 5 to 10 years under good conditions. A lithium LiFePO4 battery can easily withstand over 3500 cycles at 80% discharge, which corresponds to 10 years of daily use (and often more than 15 years with less deep discharges). In practice, many manufacturers guarantee their lithium batteries for 10 years or ~6000 cycles at 80% DOD (Depth of Discharge), with the target point at the end of the warranty usually being 70% remaining capacity. To maximize lifespan, avoid extreme temperatures (performance decreases below 0°C and above 40°C, and heat accelerates aging), and do not systematically discharge the battery to 0% if you can avoid it (leave a 20% margin for lithium if possible).

• How to test a solar battery? If you suspect a performance reduction, you can perform a capacity test. This involves charging the battery to 100%, then disconnecting it from solar power and letting it power a known device (or simulating a fixed load) until it shuts down, while measuring the energy delivered. Some batteries or inverters provide this information directly via the app. You can also check the open-circuit voltage of the battery: A 48V lithium battery, for example, has ~53V charged and ~48V at half charge – significant deviations or unusual voltage drops under load can indicate a problem. In case of doubt, contact the manufacturer's or dealer's customer service, especially if the battery is still under warranty.

• What to do in case of failure or performance degradation? If your battery no longer charges or discharges too quickly, there are several possible causes: a defective cell, a communication problem between BMS and inverter, or simply the end of the battery's life. Start with simple checks: cables properly connected, fuses not blown, charging parameters not reset by a power outage, etc. In a networked system, check any error codes in the app. Never dismantle a lithium battery yourself (risk of electric shock or short circuit that can lead to a fire): contact a professional. For open lead-acid batteries, you can check each cell with a hydrometer or measure the voltage of each cell to identify a potentially weak cell (but again, the intervention of a specialist is preferable). In general, if the usable capacity has fallen below a threshold acceptable to you (e.g., the battery only lasts 2 hours instead of the original 5), it's time to consider replacing the battery.

By following these recommendations, your solar battery will have a long and trouble-free life. The key is to choose high-quality materials from the start and use them within the intended limits. NYLYN Solar offers exactly such high-end batteries with extended warranties, ensuring your peace of mind. Do not hesitate to contact our experts for any questions regarding the maintenance of your energy storage system.

Should you use a car battery for a solar system?

Some people wonder if it is possible to use a car battery (12V lead-acid starter battery) as a solar battery, as these car batteries are readily available and inexpensive. The short answer is: No, this is not recommended. A car battery is designed to deliver a high current for a short period (starting the engine) and then be immediately recharged by the alternator. It is not designed for deep and repeated charge/discharge cycles. If you use it as a solar battery, i.e., regularly discharge it over a wide range, it will wear out very quickly (after just a few deep cycles, its capacity will drastically decrease). For solar systems, so-called "deep cycle batteries" or "cyclic batteries" are used, which can withstand cycles. It is therefore better to invest in a real solar battery (AGM, gel, or lithium) intended for this purpose; you will gain in longevity and safety.

Conversely, high-quality automotive lithium solar batteries (e.g., second-life electric car batteries) can sometimes be used for home systems, but this is still rare and requires special equipment. In summary, one should not cut corners by using an unsuitable battery: The chemistry and internal design of a battery must correspond to the intended use.

Plug-and-Play Solar Kits with Batteries: The Simple Solution

For those who don't want to design a custom system or live in an apartment, there are plug-and-play solar kits that optionally include storage. For example, kits for balconies or terraces combine one or two solar modules, a micro-inverter, and sometimes a small external battery. These pre-configured kits make it possible to produce and store some of your own electricity without major work. Installation is child's play: Mount the module, connect the micro-inverter to a power outlet, and connect the battery (if included) according to the instructions... that's it!

NYLYN Solar offers precisely a range of plug-and-play solar kits that are ideal for balconies or small systems. They include reliable micro-inverters, high-quality solar modules, and smart energy storage options, all at affordable prices. Whether you're a city tenant or a small homeowner, these kits give you access to solar energy in no time. For example, an 800W balcony kit produces up to ~800 kWh per year and can include an additional battery to store energy during the day and let you benefit from part of your production in the evening. This is an excellent way to get started with self-consumption without embarking on a major project, and it's expandable (you can often add a battery module or an additional module later).

By choosing a plug-and-play kit, you benefit from the manufacturer's expertise: everything is correctly sized, and compatibility between components is ensured. You just have to follow the instructions to produce your green electricity at home. Again, these kits can usually be easily moved or supplemented if you move or your needs change.

Conclusion: Take the Leap Towards Energy Independence!

Solar batteries and photovoltaic energy storage solutions are a fantastic asset to get the most out of your solar modules. By answering the most common questions – from how they work to installation, selection, and maintenance – we hope to have shed light on this topic for you. Whether you want to drastically reduce your electricity bill, secure your power supply in an emergency, or simply contribute to the energy transition, home storage is an increasingly accessible and profitable option.

NYLYN Solar, as an e-commerce company specializing in solar energy, offers the best products on the market to make your project a reality. We select high-performance and durable batteries as well as turnkey solar kits to guarantee you a successful experience. Do not hesitate to browse our collection for batteries and storage solutions (see link above) to discover our offers, or contact us for personalized advice. With the right solar battery, the sun will shine for you day and night – it's up to you to take the step towards clean and controlled energy.

Seize your energy autonomy today and join the growing community of solar power prosumers! 🌞🔋