The Ultimate Guide to Solar Batteries

Introduction

As the use of solar power increases, there is also an increased need for efficient energy storage solutions. Solar batteries play an important role in storing any excess energy that is generated during the day, that can be used for later use. This ensures a steady supply of clean and renewable power.

In this guide we will provide you with information on solar batteries, including their functionality, types, benefits, installation, and maintenance for residential purposes. We will look into how they store and discharge energy efficiently, and how to choose the best battery for you, depending on size, capacity, voltage, compatibility and lifespan.

Throughout the guide we will address common questions that you may have thought of yourself, and we will give you practical advice to help you make informed decisions. Hopefully, by the end of this guide you will have a comprehensive understanding about solar batteries.

Browse the guide at your own pace or open the dropdown menu to click the links to jump to the sections you need the most.

Section 1 – What are Solar Batteries?

Solar batteries, also known as energy storage systems or solar battery banks, are devices that store excess electricity generated by solar panels during the day for later use. These batteries maximise the efficiency and reliability of solar power systems, by storing and utilising the generated energy for when the sun isn’t shining.

Solar batteries work by converting and storing the direct current (DC) electricity produced by the solar panels into chemical energy. This can later be converted back into usable electricity. These batteries usually utilise rechargeable battery technologies.

This stored energy can be used to power household appliances, lighting, and other electrical devices. This helps to decrease our reliance on the electrical grid, lower our electricity bills, and provide a backup power supply during power outages.

They come in various capacities, meaning homeowners can choose the right battery for their energy needs. Solar batteries can be integrated into new or existing solar power systems, due to their flexibility and scalability.

The use of these batteries can be optimised through the use of an energy management system, smart monitoring and the participation of demand response systems. Utilising these features can also give you real time performance data.

Section 2 – Battery Types

There are various types of batteries that can be utilised within a power management system to store and provide electricity. Battery types include:

Lead-Acid Batteries: This type of battery has been used for years, due to their reliability, affordability, and they can be used in numerous applications. The two types are: Flooded lead-acid (FLA), these require maintenance, such as adding distilled water to the cells; and Sealed lead-acid that require no maintenance. These batteries have a lower upfront cost and a moderate energy density.

Lithium-Ion Batteries: These batteries have a high energy density, longer lifespan, and high efficiency. They are light, more compact and have a higher charge and discharge efficiency. These batteries are suitable for residential use. They are available as lithium iron phosphate (LiFePO4) and lithium nickel manganese cobalt oxide (NMC).

Flow Batteries: These batteries store energy in liquid electrolytes in an external tank. They are useful for their scalability and long lifespan. The most used flow batteries are vanadium redox flow batteries (VRFB) and zinc-bromine flow batteries (ZBFB). These are usually used for large scale energy storage, have a high capacity, and can help to balance the electrical grid.

When choosing the solar battery that is right for you, it is important to remember that they each have their own characteristics, such as upfront cost, lifespan, efficiency, depth of discharge, energy density and maintenance requirements.

Section 3 – Battery Factors

Battery Capacity and Voltage

The capacity and voltage of a battery is an important consideration when implementing a solar power system with a battery.

The battery capacity is the amount of energy the battery can store, usually measured in ampere hours (Ah). This represents the total charge the battery can deliver over a certain amount of time before it needs recharging.

When choosing a battery capacity take into consideration your daily energy consumption, autonomy requirements or how long the battery will last without recharge, and the availability of solar energy.

Battery voltage determines whether it is compatible with other components, including solar panels, inverters, and charge controllers. Commonly for solar applications the battery voltages will be 12V, 24V or 48V systems.

When choosing the voltage of a battery consider the systems design, power requirements and the availability of equipment that is compatible. Larger scale systems usually require a higher voltage, however, always make sure the voltage of the battery aligns with the systems voltage requirements.

Battery Sizing and Capacity Planning

The first step to sizing solar batteries is to assess the requirements for energy consumption and load of the system. Therefore, daily usage, peak power demands and desired backup power duration need to be considered, to estimate the amount of energy that needs to be stored.

Once the estimate has been made, the battery capacity required needs to be calculated. Battery capacity is measured in ampere hours (Ah), which is the amount of energy that can be delivered per hour. This can be calculated by dividing the energy requirement (in watt-hours) by the battery voltage.

Also consider the battery’s depth of discharge (DoD), as it determines how much the battery’s capacity can be utilised before it needs to be recharged.

The desired backup power duration will affect the battery capacity needed. For shorter durations, a smaller capacity will be required. For longer backup power durations, larger capacities will be required.

To ensure the system can meet the energy needs effectively, it needs to be efficient and have safety margins in place.

Depth of Discharge

The Depth of Discharge (DoD) represents the percentage of the battery’s total capacity that has been discharged before it needs to be recharged. Therefore, you can see how much energy has been extracted.

Batteries that have a lower DoD will usually have a longer lifespan, this is due to deeper discharges putting more strain on the battery, which reduces its lifespan. A lower DoD will cause less strain, increasing its lifespan.

The cycle life of the battery refers to how many times it can be recharged before its performance degrades. A shallower discharge allows a higher number of cycles before it starts to degrade.

To maximise the lifespan of the battery, operate solar batteries within a specified DoD range. This range depends on the battery chemistry and the recommendations from the manufacturer.

When designing a solar battery system, it is important to consider the desired DoD and ensure that the battery’s capacity size meets the energy storage needs. Oversizing the battery capacity within the recommended range reduces the strain on the battery and extends its lifespan.

Battery Efficiency

When assessing the performance and usable capacity of a battery it is important to consider solar battery efficiency.

Battery efficiency refers to the ratio of the energy output of a battery to the energy input during charging and discharging. It considers how effectively a battery converts stored energy into usable electricity. Efficiency is influenced by factors including chemical composition, temperature, charge/discharge rates, and battery age.

High efficiency means less energy lost and better overall performance.

Battery Lifespan

The lifespan of a solar battery is the duration it remains functional and provides a usable amount of energy. It is influenced by factors such as the battery chemistry, its operating conditions, maintenance, and usage patterns.

The lifespan can also determine how many cycle-lives a battery has, depending on the type, typically a battery can have hundreds to several thousand cycle-lives, before it starts to degrade.

Lifespan can also be affected by a battery’s depth of discharge (DoD). Deeper discharges can increase battery degradation and decrease its cycle-lives. Manufacturers usually recommend DoD limits to increase performance and longevity.

Battery Management Systems can play an important role in extending the lifespan of a battery. As they monitor and regulate parameters to ensure safety and efficiency, they can mitigate against reduction to the battery’s lifespan through cell balancing, temperature control and voltage control.

Taking care and maintaining the solar battery will protect the lifespan of the battery. Such as through regular monitoring, maintaining an appropriate temperature, avoiding overcharging, avoiding deep discharge, and sticking to the manufacturer’s guidelines.

Section 4 – Battery Management Systems (BMS)

Battery management systems can increase the performance of longevity of a solar battery through monitoring and controlling various parameters. Features include:

Monitoring State of Charge (SoC): The BMS will continuously monitor the state of charge of the battery, measuring the amount of energy stored compared to the capacity. This shows the user how much energy is left and helps them to not overcharge. This can help to prevent damage or failure of the battery.

Voltage Monitoring: The BMS measures the batteries voltage levels, to make sure it is within its safe operating limits. This can prevent overcharging that can lower the batteries lifespan and prevents excessive discharge, which can cause irreversible damage.

Temperature Management: The BMS will monitor the temperature of the battery to prevent overheating, which can degrade the battery and shorten its lifespan. It can also compensate the temperature during the charging and discharging process.

Cell Balancing: In multi-cell battery systems, the BMS ensures each cell is balanced by equalising the charge levels, allowing a consistent performance, and increasing efficiency.

Fault Detection and Protection: The BMS detects and triggers protective measures for faults, including over- and under-voltage, overcurrent, and short circuits. The protective measures include disconnecting the battery or activating a safety mechanism.

Data Monitoring and Reporting: The BMS provides real-time data on key battery parameters, including SoC, voltage, temperature, and previous performance data. Key decisions can be made about the battery’s health, such as for maintenance, optimisation, and system upgrades.

Section 5 – Battery Charging Methods

Solar battery charging methods help to efficiently and effectively charge solar batteries. They can optimise the charging process and maximise the capacity and lifespan. The three main methods are:

Constant Voltage (CV): The battery is charged at a constant voltage level. Initially it charges at a high level, then decreases as it charges. When the battery is at full capacity, charging maintains a constant voltage to keep it topped up. This method is usually used for lead-acid batteries.

Constant Current (CC): This method delivers a constant current to the battery as it charges. As the battery charges, the voltage gradually increases until fully charged. The charger monitors the voltage and adjusts the current accordingly, creating a faster charge. This method is usually used for lithium-ion batteries.

Maximum Power Point Tracking (MPPT): This method utilises the charge controller to continuously adjust the voltage and current to find the maximum power point. They can also match the varying voltage and current to the optimal charging characteristics of the battery to increase energy generation. This method is used when the solar panel output is higher than the battery’s voltage. It is usually used for grid-tied or off-grid solar systems.

Section 6 – Battery Safety

• Make sure that the solar battery is installed following the manufacturer’s guidelines and applicable electrical codes, to ensure safety. It may be necessary to hire someone with adequate training to install the solar battery.
• The battery should be protected from overcharging to prevent degradation, reduction to lifespan and safety hazards. Charge controllers and battery management systems can do this.
• Protect the battery from overheating, as excessive heat can negatively affect the battery’s performance and safety. Install batteries in cool and ventilated areas, away from heat sources and direct sunlight.
• Protection against short circuits can prevent thermal runaway, which can cause battery failure and fires. Securely covering the battery terminal, using proper insulation, wiring, and fusing should prevent this.
• It is important to follow the proper handling procedures and safety precautions when working with solar batteries, such as PPE, gloves, and safety glasses.
• Regular maintenance such as cleaning and checking for damage should ensure safe operation.
• To mitigate the risk of a fire, safety measures should be put in place, including smoke alarms, fire extinguishers and an emergency response plan.

Section 7 – Battery Maintenance

• Regularly inspect the batteries for signs of damage, corrosion, and leakage. Check battery terminal, cables, and connections to make sure they are clean and secure. Address any issues as soon as you notice them.
• Keep battery surfaces clean and free from dust, dirt, and debris. Use a damp cloth to clean the battery terminals and connections. Avoid abrasive materials and harsh chemicals.
• Perform periodic equalisation charging to maintain the battery’s capacity and balance the individual cell voltages.
• Replace any faulty or ageing batteries promptly.
• Ensure that batteries are in areas with suitable temperature control, as extreme temperatures can impact the battery’s performance and lifespan.
• Make sure to regularly monitor the solar power systems performance, including charging and discharging cycles. Use monitoring tools or software to track energy production, battery voltage, and state of charge.

Section 8 – Different Battery Systems

Hybrid Solar Systems with Batteries: This system combines the benefit of solar panel with an additional energy source, such as the electrical grid or a diesel generator. Integrating solar batteries allows energy to be stored to create a constant reliable power supply. Excess solar energy can be stored for later use, to decrease the reliance on the other energy sources. These systems provide flexibility, increase energy independence, and can reduce energy bills. Hybrid Solar Systems prioritise the solar energy, and they can be used in residential settings.

Off-Grid Solar Systems with Batteries: These systems are designed to provide electricity to remote areas and areas that have no access to the electrical grid. The solar batteries in these systems store excess solar energy during the day to be used at night or in periods of low solar generation. This allows there to be a continuous power supply. The batteries act as a backup so off-grid users can rely solely on solar energy.

Grid-Tied Solar Systems with Batteries: These systems combine solar power with the ability to store excess energy for use during grid outages or peak demand periods. They are connected to the electrical grid which allows users to sell any excess solar energy back to the grid for credits or compensation, whilst also storing their own energy in batteries. Owners can then benefit from a continuous energy supply, whilst reducing their reliance on the grid.

Section 9 – Energy Management Systems

Energy management systems (EMS) are important for optimising the use of solar batteries within a solar power system. They are designed to monitor and control the energy flow, to increase efficiency and maximise self-consumption.

Depending on factors, including energy demand, solar generation, grid conditions and time of use tariffs, the EMS will co-ordinate the charging and discharging of the solar batteries. They do this by analysing real-time data and determining the optimal balance between the energy supply and demand.

One of the EMS’s primary functions is to prioritise self-consumption, by controlling the flow of energy and directing any excess energy towards charging the battery instead of feeding it back into the grid. When energy is needed, including times of high energy demand or when solar generation is low, the EMS utilises the energy from the battery instead of the grid.

The EMS also enables load shifting, which involves storing excess solar energy in batteries for use during peak demand periods when energy costs are higher. By managing the energy flow an EMS can result in potential cost savings.

Advanced EMS systems can integrate smart home technologies, these allow users to remotely control and monitor their energy consumption and helps them to make informed decisions.

Section 10 – Battery Integration with Solar Inverters

Solar inverters are responsible for converting the direct current (DC) electricity that is produced by the solar panels to alternating current (AC) electricity that can be used or fed back into the electrical grid.

They are also important when charging and discharging the batteries. Hybrid inverters are designed to integrate the solar panel and battery into a single unit. They have built in charge controllers that regulates an efficient energy flow to and from the battery. These inverters simplify the installation and operation of a solar power battery system.

When separate charge controllers are used, they work alongside the solar inverters to manage the charging of the batteries. The charge controller monitors the state of charge of the batteries and regulates energy flow from the solar panels to ensure optimal charging. This safeguards the battery from overcharging and deep discharging.

Section 11 – Economic Analysis of Solar Batteries

The cost of solar batteries has been decreasing over the years, meaning they are becoming more affordable and accessible. The cost can be influenced, however, by the brand, the battery chemistry, and capacity. It is important that the cost of these different options is compared to the lifespan and the performance of the battery, before purchasing.

The return of investment (ROI) of solar batteries is determined by the savings made through load shifting and peak shaving. Load shifting involves storing excess energy for later use, allowing users to lower their reliance on the grid and lower their energy bills. Peak shaving is when battery power is used during times where energy demand is high reducing the need to take power from the grid and saving on peak demand charges.

Potential savings from both of these depends on factors such as electricity rate structure, time of use tariffs, and the availability of feed-in tariffs or net metering. It is recommended that a cost-benefit analysis is carried out to estimate the financial viability of the solar battery.

In areas prone to power outages or for critical applications that require a reliable power source, solar batteries can provide backup power, ensuring an uninterrupted electricity supply.

It is important to remember that batteries have a limited lifespan, and their performance will degrade over time. When choosing a battery consider its lifespan and its warranty coverage, as this can help to assess its long-term financial benefits.

Section 12 – Environmental Impact

The environmental impacts of solar batteries fall into their various aspects, including manufacturing, recyclability, and disposal methods. Although they offer significant benefits, such as renewable energy, it is also essential to consider their environmental implications throughout their lifecycle.

The manufacturing process typically involves the extraction and processing of raw materials, including lithium, cobalt, nickel, and other metals. Each of these extraction processes have environmental impacts, such as habitat destruction, water pollution, and carbon emissions. There is, however, efforts being made to improve the sustainability of these processes to reduce emissions and implementing responsible sourcing practices.

Batteries contain valuable materials that can be recycled, recovered, and reused, which reduces the demand for new raw materials and minimises waste. There has been an increased demand for efficient battery recycling processes, to ensure valuable materials are reused and environmental damage is significantly reduced.

To prevent environmental contamination, proper disposal methods need to be adopted. Batteries contain hazardous materials, and incorrect disposal can lead to the pollution of water and soil. Recycling programs and regulations are being put in place worldwide to prevent this.

When compared to fossil fuel-based energy storage methods, solar batteries have significantly lower carbon emissions, meaning they have a significantly lower environmental impact.

The environmental benefits of solar batteries are enhanced when they are combined with a renewable energy source, such as solar panels. As solar energy is stored for later use, there is a lower reliance of fossil fuel-based energy, creating a cleaner and more sustainable energy system.

Section 13 – Policy and Regulations for Solar Batteries

Net metering has been implemented by the UK Government to encourage the use of solar batteries within the UK. Through net metering, owners can export excess electricity back to the grid to receive credits or compensation. This allows homeowners that have solar batteries to offset their energy consumption and potentially earn revenue.

Time off use tariffs provide different electricity rates based on the time of day. This promotes the use of stored energy during peak demand times when electricity prices are higher. This incentivises owners to store energy during low demand periods and discharge it during high-demand periods, helping to balance the grid and reduce strain during peak hours.

The UK Government also supports the integration of solar batteries into energy storage markets. These markets allow solar battery owners to participate in grid services, such as frequency regulation and peak shaving. By utilising stored energy, owners can support the stability and reliability of the grid, whilst also potentially generating additional revenue.

Financial incentives and grants are provided by the UK Government to support the deployment of solar batteries. This includes the Smart Export Guarantee (SEG), which allows owners to receive payment for any excess electricity exported to the grid.

The government also offers grants and funding schemes to encourage the installation of energy storage systems, such as solar batteries, within residential settings.

Section 14 – Economy 7

‘Economy 7’ is an electricity tariff that provides various electricity rates depending on the time of day. The tariff is usually offered by energy providers and involves two distinct periods:

1. Cheaper, off-peak period during the night
2. More expensive, peak period during the day

The aim of the tariff is to encourage consumers to shift their electricity usage to off peak hours when there is less demand for electricity. This helps to balance the load on the electrical grid, for certain appliances, such as electric storage heaters, water heaters, and electric vehicle (EV) batteries, this can be cost effective. Especially during winter months, when the temperature drops, and the use of heaters increases.

If you want to use the Economy 7 tariff, make sure:

• It is available in the region you are in, and check eligibility. To do this contact your energy provider or check their website for available tariffs.
• Make sure you have a specialised meter, if not contact your energy provider to arrange a meter replacement.
• Make a schedule, so that you can take advantage of the cheaper rates during specific off-peak hours, which are usually at night.
• Invest in a battery charger that is suitable, some batteries allow you to set the charging time.
• For electric vehicles, check if they have a scheduling or timer feature, to start the charging times for off-peak hours.
• Monitor your usage and bills to make sure you are benefitting from the Economy 7 tariff.

If you have a high electricity consumption, especially during winter months, Economy 7 can help to lower your electricity bills. Make sure you contact your energy provider for more details.