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Solar batteries in deepth


Solar panels produce electricity, which is stored in batteries for later use. Batteries are not required for all solar power systems. If your facility has access to an electric power supplytt an on-grid system is the best choice. “Batteries are not necessary for all solar energy systems.” You will need to spend money on a machine without a grid connection if connecting to one is not a practical alternative. You need a backup location to keep the energy you produce because you can’t store it online. Batteries are required there. Off-grid solutions are powered by batteries. They store the energy your solar panels produce so it is always available when you need it. There is a third system type in addition on-grid connected systems with battery in just in case.

Basic three types of solar batteries

For a solar system, there are three basic battery types: lithium-ion, sealed gel batteries, and flooded lead-acid batteries (FLA).

A premium choice with a great price is the lithium battery. In terms of performance and cost, FLA and GEL batteries are more comparable to one another. Even though lithium batteries are a more recent invention, lead batteries have been used for 150 years. Lead-acid batteries come in two varieties: flooded and sealed or gel.

Flooded lead acid batteries (FLA) are designed to withstand a daily charge cycle. They emit hydrogen gas as a by-product, so they must be properly ventilated. To function properly, the plates of each cell must be flooded with water.

To keep the plates flooded, water should be added every 1 to 3 months. The time between adding water is determined by temperature, discharge, and other factors, but it should be checked at least once a month. Charge equalization, which is controlled overcharging that helps restore the battery’s FLA, is another required maintenance step. It would be ideal if the charge was equalized every three months, or as needed. Equalizing the charge helps prevent sulfation of battery plates and can also be used to correct cell or battery imbalances.

FLA batteries are ideal for people who prefer to work on their own system. They are the most affordable option, but they require regular maintenance for proper functioning. If you won’t be able to inspect your battery on a regular basis, sealed lead-acid batteries are a better choice.

Sealed lead batteries ( AGM and GEL)

These batteries are not dangerous because they cannot leak. AGM (absorbing glass mat) and GEL are two types of sealed lead acid batteries with very similar characteristics. Sealed batteries are a complete system. Unlike submerged batteries, they do not require filling with water.

As a result, they work well on properties that are not constantly active, such as a vacation home that is only used a couple times a year. Sealed is not connected to the network you are connected to self-discharge so quickly if they are idle for a long time while you are batteries will not you are connected to self-discharge so quickly if they are idle for a long time while you are accumulators will not you are.

Lithium-Fero-Phosphate (LFP) batteries

Lithium batteries are a newer technology that first appeared on the market in the 1970s. Typically used for laptops and mobile phones, they have recently gained popularity in renewable energy spaces. There are various types of lithium batteries. The offline solar energy chemistry of the lithium-iron phosphate battery (LiFePO4 or LFP) has been designated as safe and durable for domestic use. Lithium batteries are more expensive, but there are several benefits that outweigh the cost.

  • longer shelf life due to a lack of maintenance Enhanced energy efficiency
  • Longer usable storage capacity (slower discharge) No flammable gases or ventilation


Solar batteries key terms

The amount of energy that a battery can store and deliver to your devices is referred to as its capacity.

This is determined by the voltage, amp hours, and discharge rate. Kilowatt hours (kWh) are units of measurement for energy consumption over time. This formula can be used to calculate the total storage capacity of a given bank battery based on voltage and ampere-hours: Voltage x Ampere-hours = capacity (in Watt-hours).

For example, 12 V x 100 Ah = 1200 W. A 12-volt battery with a capacity of 100 amp-hours generates 1,200 watt-hours (1.2 kilowatt-hours) of energy.

Bank of Batteries: A group of batteries that have been wired to work with an inverter or a charging regulator at a specific voltage (for example, 12, 24, or 48 volts) and capacity (e.g., 400 amp-hours).

Voltage is the unit of measurement for batteries. Lead-acid batteries typically have voltages of 12 volts, 6 volts, or 2 volts, and multiple batteries are connected in series to achieve the desired voltage.

Smaller systems can typically use 12 volt batteries, whereas larger systems will require 6 or 2 volt batteries with a higher ampere-hour capacity. Most lithium batteries for off-grid solar systems are not in the configuration of 12 volts, 24 volts, or 48 volts. Cycle: Each time the battery is discharged and recharged, it completes one cycle. The best way to estimate actual battery life is not based on time (for example, a two-year warranty), but on the estimated working life of the cycle—how many times the battery can be charged and discharged during its working life.

Depth of Discharge (DOD): The quantity of battery energy that discharges during each charging cycle For instance, if you use the battery at a 75% depth of discharge, it will be used to its full capacity before needing to be recharged.

DOD is a key factor in deciding how long a battery will last. When lead batteries are discharged shallowly, they live longer and deteriorate more quickly than when they are discharged deeply to emptiness. Efficiency Batteries are not entirely efficient. One portion loses strength during the filling and emptying procedure. Lead-acid batteries have an efficiency range of 80–85%, while lithium batteries have a range of 95–8%. For instance, due to inefficiencies in the charging and discharging processes, lead acid batteries could only store roughly 800 W if your solar panels produce 1000 W of energy. Under identical conditions, you would have 950 Wh available from a lithium battery.

Battery bank

Battery sizing for off-grid systems is a relatively simple process. You can choose cheaper lead batteries or lithium batteries. Then, look at your daily electricity needs and multiply them by the influencing factors of the selected battery. Battery efficiency factor, depth of discharge, voltage converter efficiency, and ambient temperature are the influencing elements taken into consideration. These numbers for lead accumulators are roughly: 1.2, 2′, 1.05, and 1.11. These are the lithium battery values: 1,05, 1,25, 1,05, 1,05, and 1,05. More precise data can be obtained from the manufacturer of the battery and the type you have chosen. After determining the battery bank’s minimum daily capacity, we size the solar array (as well as the backup generator) such that they can be built to regularly charge the batteries. Because a lithium battery can survive a deeper discharge and has greater efficiency, it has a smaller overall capacity.


Generaly speaking, larger systems with larger converters and more battery capacity use the higher voltage (24 or 48 volts). This is so that you can install more solar power on each charge controller, as higher voltage is more efficient, utilizes fewer wires, and does so. A voltage-neutral converter uses 24 or 48 volts.

System voltage depends on a number of variables, but the best place to start when building an off-grid system is with battery capacity (measured in kilowatt-hours). Learn how much energy you require from the battery each day and then modify the other components of the system (such as panels and inverters) to fulfill that need.

Miroslav Mitić

Mechanical engineer and programmer for 25 years. Solar energy expert

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