storage devices for electrical energy. Use this tag for questions about selecting and using the (most sustainable) various battery technologies for a particular application as well as questions about the number, size, and wiring of batteries into an electrical system. The later is also on topic on electrical engineering SE
A battery is a device for the storage of electrical energy. The applications for which a battery is acceptable will depend on how the battery is used in the device or electrical systems being designed.
There are two main types of batteries: primary batteries and secondary batteries.
A primary cell or primary battery is assembled from materials which create a battery that is already charged and able to provide electricity. These batteries are made up of materials and designed so that they are a source of electrical energy after being assembled. These batteries are not designed to be recharged and should not be.
A secondary cell or secondary battery is assembled from materials which create a battery that needs to be charged. These batteries are made up of materials and designed so that they can store electrical energy once they are charged. These batteries are designed to be recharged.
Both primary batteries and secondary batteries come in a large variety of sizes and materials and technologies. Different materials provide different operational characteristics such as recharge or not, how many times a battery can be recharged, and how does recharging affect the capacity of the battery over time.
The basic characteristics of a battery, shared by both types, is the voltage the battery is designed to provide and the amps of electrical energy that can be stored in the battery.
Batteries may be connected in series to provide a higher voltage with the same amps or they may be connected in parallel to provide the same voltage with higher amps.
In other words two 9 volt batteries each of which has 500 milliamps can be connected in series to provide a single 18 volt battery of 500 milliamps or can be connected in parallel to provide a single 9 volt battery of 1,000 milliamps capacity.