Solar batteries are an important investment in solar photovoltaic energy installations, so it is essential to choose the right type and quantity you need. To do so, it is necessary to take into account both the different types of existing technologies and the use that will be made of the installation.
In this article we explain the process to follow to choose and size a battery system for a solar panel installation.
Types of batteries for solar panels.
Nowadays there are different types of solar batteries that can be adapted to different installations and modes of use. It is important to know their characteristics and differences before choosing one or another.
There are two main ways to classify solar batteries: by their format and by the technology they use.
In terms of format you can find:
- Monoblock batteries: small size, similar to a conventional car battery. They have less capacity and useful life than stationary batteries, so they are used for small installations, but in exchange they have a lower cost.
- Stationary batteriesStationary batteries: larger in size and with a greater electrical charge capacity, in addition to having a longer useful life. They are more suitable for medium and high consumption.
If we talk about the type of technology can be found:
- Open lead acid batteries: they require annual maintenance of the electrolyte level, have a useful life of about 1500 charge cycles and a discharge capacity of 50%. In addition, they cannot be used indoors due to the evaporation of gases produced.
- AGM batteriesAGM batteries: use a special electrolyte that does not require maintenance, so the batteries are sealed and do not suffer evaporation. They usually have a useful life of 1000 cycles and their discharge limit is around 60-70%.
- GEL batteriesThe electrolyte is in the form of gel, so they are also sealed batteries and do not require maintenance. Their useful life is between 800 and 1500 charge cycles and their discharge limit is 60-70%.
- Blithium batteriesLithium batteries: this technology offers superior performance, with a useful life of 6,000 charge cycles, a discharge limit of close to 100% and no maintenance required. On the other hand, their price is higher than the previous ones.
How to calculate the batteries needed for a solar panel installation.
When calculating the batteries needed for your installation, the first thing to do is to determine a series of questions about their use and operation.
- Supply capacity: days that the house can be supplied with the energy stored in the batteries. If it is an isolated installation, it can be a period of 2 to 6 days, for example, enough to withstand bad weather spells. If it is a weekend house, it may be less.
- Consumption to coveri.e., how much electricity you consume at home. For this you can use past bills or estimate what consumption you are going to have depending on the devices you have, such as lighting, appliances, solar pumping system, etc.
- Estimate the capacity you needThe capacity is the multiplication of your consumption by the number of days of autonomy you have estimated. Batteries are an expensive component, so it is important to adjust the calculation so that you do not have too much but not too little capacity.
Example of battery calculation process for an installation.
Let us assume that this is a weekend home installation, so we define a supply capacity of 3 days, enough to be able to spend a weekend only with the batteries.
We estimate the consumption we make, including lighting, a TV, a fridge and some small appliances. In total we get 2500 Wh/day of consumption.
Analyzing these data we could opt for GEL or AGM batteries, with a 12 V installation. The depth of discharge of these batteries, as we have said, is 70%, something that we must also take into account.
We recapitulate the data:
- Daily consumption = 2500 Wh/day
- Days of autonomy = 3
- Depth of discharge = 0.7
- Voltage = 12 V
- In addition, we will add a safety margin of 15% to compensate for installation losses.
Capacity = (2500 * 3) / (0.7 * 24) = 892.85 Ah +15% = 1026.8 Ah
With this, it only remains to look for a battery model that allows us to create a storage system with a capacity higher than that figure, for example, using 4 AGM batteries of 288 Ah each.
Choose the best batteries for each project.
The calculation and design process of the battery system is an important part of the installation budgets, since it is a component that has a strong impact on the final price. That is why it is advisable to have a system that allows you to take into account both the characteristics of the installation and the user's consumption profiles in order to obtain the batteries that best fit the project.
Wattwin can help you with this task. If you are interested you can contact us to request a demo.
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Very interesting and useful content, thanks for the information!