When electricity is generated it must be immediately used. However, there will be times when your solar power system will be generating more power that you can personally use at that moment. If your system is not tied to the power grid then you can use batteries to store some of that energy for later use, when the sun is not shining.

Batteries use a chemical reaction to produce electrical current. The process of charging a battery reverses the chemical reaction. With each charge-discharge cycle the battery will loose a small fraction of its capacity permanently. However, when treated with care, the batteries in your system can perform well for many years.

Large capacity battery banks usually employ low voltage cells connected in series to provide the desired DC voltage. These batteries require maintenance to replace water lost in the charging process.

Smaller setups can use sealed batteries that require no maintenance. Sealed batteries use a gelled electrolyte (gel cells) or fiberglass sheets permeated with electrolyte, these are known as absorbed glass mat or AGM batteries. Gel cells and AGM batteries can be installed in any orientation without the danger of spilling the corrosive acid inside, making them ideal for marine applications or harsh environments.