Lithium batteries for solar systems

Lithium batteries allow energy to be stored to be used when it is really needed and in a solar energy system they can conserve part of the electricity produced by the photovoltaic panels and make it available later, for example at night, during periods of low solar production or in the event of certain power outages.

Adding batteries doesn’t simply mean adding more equipment to an installation; the capacity, battery type, and configuration of the system must work together and respond to consumption, the loads to be supported, and the level of autonomy sought.

Within a photovoltaic system, different components work together to produce, manage, store and use energy.

• Solar panels (Generator): They are responsible for capturing solar radiation and transforming it into direct current electricity (DC or DC).
• Lithium battery (Storage): The most common for solar systems are LiFePO4 (or LFP) technology, valued for their long lifespan and safety.
• Charge controller (Regulator): Regulates the energy intended for storage and protects the operation of the battery. Depending on the system architecture, this function can be found in a stand-alone device or integrated into the inverter.
• Inverter (Converter): Converts direct current (DC) from the panels and battery into alternating current (AC or AC), which is the type of electricity used by most appliances in the home.

Its popularity is due to several advantages over older technologies, such as lead-acid batteries:

• Minimal maintenance: They do not require frequent maintenance or special ventilation systems.
• High efficiency: They make better use of stored energy and have a higher energy density, which means they store more energy in less space.
• Long useful life: They withstand a high number of charge and discharge cycles, some having a useful life of up to 20 years.
• Fast charging: They charge in less time compared to other technologies.

There is no adequate battery capacity for all homes or businesses, which is why calculating the battery you need for your solar system is a process that is based on understanding your consumption and defining how much range you want. Sizing should start by identifying which equipment should work and for how long.

• Calculation of daily energy consumption: This is the starting point, as it is necessary to know how much the property consumes and how that consumption is distributed during the day. The easiest way is to review your electricity bill and divide your monthly consumption (in kWh) by 30
• Loads to be backed up: It is not always necessary to power absolutely all the equipment during an outage. In many projects, priority loads are identified, such as lighting, cooling, communications, security systems, work equipment or other devices important to the operation.
• Hours of battery life: Holding a charge for two hours requires a very different capacity than holding it for eight hours. The expected backup time has a direct relationship to the storage needed.
• Maximum power of loads: In addition to storing enough energy, the system must be able to supply the required power when several pieces of equipment are operating simultaneously.
• Photovoltaic production: When batteries are part of a solar system, it must also be studied how much energy the panels can produce and how much of that production will be available to charge the storage.
• Losses and operating reserve: A real design must consider the losses that occur during energy conversion and storage, in addition to the recommended operating limits for each piece of equipment. For these reasons, sizing a battery bank requires analyzing the entire system and not just choosing a capacity in kWh.