A solar battery is a device that stores electric charge in chemical form, and you can use that energy at any time, even when your solar panels are not generating power. Although the battery backup systems that are coupled with solar panels are often referred to as solar batteries, they can store charge from any electricity source. This means you can recharge a battery with grid power when solar panels have low productivity, or you can use other renewable sources such as wind turbines.

There are different types of battery chemistries, each with advantages and limitations. Some types of batteries are suitable for applications where you need a large amount of energy in a short time, while others work best when you need a steady output over a longer period. Some common chemistries used by solar batteries are lead-acid battery, lithium-ion battery, nickel-cadmium and redox flow.

When comparing solar batteries, you should consider both the rated power output (kilowatts or kW) and energy storage capacity (kilowatt hours or kWh). The rated power tells you the total electrical load you can connect to a battery, while the storage capacity tells you how much electricity a battery can hold. For example, if a solar battery has a rated power of 5 kW and a storage capacity of 10 kWh, you can assume:

The battery can power up to 5,000 watts (or 5 kW) of the electrical load simultaneously.

Since the battery stores 10 kWh, it can sustain a maximum load of 5 kW for two hours before depleting its charge (5 kW x 2 hours = 10 kWh).

If the battery powers a smaller load of only 1,250 watts (or 1.25 kW), it can last for eight hours with a full charge (1.25 kW x 8 hours = 10 kWh).

It’s important to note that the rated power of solar panels and battery storage systems are not the same. For example, you could have a 10 kW home solar energy system with a battery that has a rated power of 5 kW and 12 kWh storage bank.