Photovoltaic Storage Batteries: Characteristics, Types, Cost, And Duration

Photovoltaic Storage Battery allows you to manage the electricity flexibly produced by the Photovoltaic System. This component allows energy to be stored when electricity consumption is lower than production, to cover energy needs when electricity consumption exceeds generation capacity.

Just as it is important to know How a Photovoltaic System with storage works, to fully exploit the advantages of solar energy it is equally important to know all the potential of Photovoltaic Storage Batteries, which types exist, how much they cost and how long they last.

Read more: Energy Diagnosis

The Characteristics of Batteries for Photovoltaic Storage

When you choose a photovoltaic system with storage it means that the system is equipped with special batteries, components that allow you to store the electricity generated and not immediately consumed. 

The energy stored in the batteries can be used at any time, for example during the night hours or during periods of low solar radiation, when the system does not produce enough energy to cover its energy needs.

Photovoltaic Storage Batteries Characteristics

The batteries can be monodirectional, therefore charging only from the photovoltaic system, or bidirectional and being charged from both the photovoltaic system and the grid. They can be mounted between the photovoltaic panels and the inverter (production side), but also after the inverter (post-production). An important characteristic is linked to the size of the photovoltaic storage batteries so that the storage capacity is adequate for the type of system and the electricity consumption of the user.

The Market for Photovoltaic Storage Battery

In particular, it is essential to correctly size the batteries, to avoid unnecessary and excessive expenses with an oversized system, while at the same time avoiding that the storage is not sufficient to cover the energy demand at times of lower production of the system. There are various sizes on the market for the photovoltaic storage battery, among which you must choose the right solution considering your energy needs and the space available to install the battery pack.

The Dimensions of Lithium Batteries

Generally, the dimensions of lithium batteries depend on the type of battery, which differs depending on the brand and model, and on how they are arranged, lying down or standing up. The weight, however, can range from 60 to 150 kg. Among the characteristics to be evaluated, are also the operating temperature, the manufacturer’s guarantee regarding the number of cycles, the degree of efficiency, and the peak and continuous power, as well as the capacity of the batteries. 

The choice also requires the calculation of the electricity consumption profile, carried out by specialized professionals to understand the right size of the batteries based on the energy needs of the home.

Read more: 4kw Photovoltaic System Price

Types of Batteries for Photovoltaic Storage

As far as technology is concerned, Photovoltaic Storage Batteries currently on the market are of only one type: lithium-ion batteries. These are components characterized by a longer life compared to existing models in the past, such as lead-acid batteries, and they also support a discharge of up to 80% of capacity without losing efficiency. The useful life of lithium batteries for photovoltaic storage is approximately double that of old batteries in circulation, with short charging times.

The main difference between lithium photovoltaic storage batteries and the previous lead-acid ones is mainly linked to cost. Lithium-ion ones have a higher purchase price but have a longer shelf-life and excellent energy efficiency.

However, considering the capacity of the batteries for photovoltaic storage, there are various solutions on the market suitable for every type of need. This characteristic must be evaluated very carefully by qualified experts, taking into account the specific consumption of each user. 

In any case, generally, the storage power is 50-100% higher than the peak power of the photovoltaic system. Here are the main types of lithium batteries by capacity:

3kW Photovoltaic Storage Batteries: 

In this case, it is possible to use lithium batteries of approximately 5kWh, to be combined with a 3 kW inverter to optimize the percentage of self-consumption, compatible with 3 kW photovoltaic systems. The system can be made up of 1 or 2 battery modules;

6kW Photovoltaic Storage Batteries: 

This type of system requires batteries with a capacity of at least 9.6kWh, with the possibility of reaching up to 12 or 14 kWh based on your energy needs. The battery pack can be made up of 2 to 6 modules depending on the capacity of the single module.

12kW Photovoltaic Storage Batteries:

These are systems suitable for a condominium or a small business, for which lithium batteries with a capacity of approximately 20-40 kWh are needed. In these circumstances it is preferable to use modular systems, to expand the capacity of the battery park based on the consumption profile.

How much does a Photovoltaic Storage Battery Cost?

The cost of storage batteries for photovoltaics depends on various factors. The price is conditioned by the technology (lithium or lead-acid), the level of energy efficiency, the charging depth, and the quality of the battery module cells.

The same applies to capacity, operating temperature, and integrated features, such as smart systems for remote management. We must also consider the cost of labor for installation, the possible need to install a new photovoltaic inverter, and the costs relating to bureaucratic formalities.

The Turnkey price of lithium batteries for the storage of a photovoltaic system is around 900-1,200 euros per kWh.

How Long Do Photovoltaic Storage Batteries Last?

An important aspect to take into consideration is the autonomy of Photovoltaic Storage Batteries. This characteristic depends on a series of factors, such as the technology used and the quality of the modules, however, it is measured in complete charge cycles, a bit like what happens with the lithium batteries of modern smartphones. 

For this reason, the life of Photovoltaic Storage Batteries is linked to the number of recharges, so the more the accumulation is charged and discharged, the shorter the useful life of the storage system will be. Today, most batteries on the market have a 7-year manufacturer’s warranty, so their operation is ensured for no less than 84 months from the moment of installation. 

As regards the number of charging cycles, however, the best quality products have a useful life of up to 10,000 cycles, therefore approximately 15 years of use. In these cases, it is always necessary to check the minimum residual capacity guaranteed by the manufacturer this value should be at least 75%, below which the batteries become inefficient and it is advisable to consider replacing them.

Photovoltaic Storage Battery Discharges Itself: Causes and Solutions

The correct functioning of storage batteries for photovoltaics depends on the quality of the installation, from the choice of the suitable place to mount the battery park to an adequate configuration of the storage system with the photovoltaic system and the home’s electricity grid. 

If the storage battery has problems, for example, it discharges itself and does not maintain its charge level, the causes could be different. For example, batteries may be exposed to a temperature outside the compatibility range, with exposure to thermal values ​​that are too low or excessively high.

Another possible reason could be an electrical fault, or a malfunction of the inverter, problems that can make the storage completely unusable. In other cases, the defect could be due to the number of charging cycles, beyond which the battery must be replaced because it no longer guarantees optimal levels of energy efficiency. 

In these situations you must never intervene personally, to avoid causing damage to the system and putting your safety at risk, but it is necessary to call a specialized professional to inspect the battery bank, identify the causes of the problem, and evaluate the possible solutions.