Basics of Batteries

What is Battery ?

A battery is a device which can store electrical energy chemically.  Let’s take a simple example of water storage. Drinking water have some specific sources, you cannot take those sources with you. So you use water bottles to store some amount of water.


Moreover if you want to store water for many days than you have to use big water storage tanks for storing purpose. In the same way large batteries like lead acid batteriesuse as large storage tank of electricity and small batteries like lithium ion (most commonly cell phone ) batteries use as small bottles of electricity.

Figure 1 : Cell and Battery

Why we use Battery ?

     Use of electricity is increasing day by day. Cell phones, laptops, cars, watches are some examples which are not able to run without electricity and at the same time you have to carry them with you for daily life usage. You cannot connect these things with electricity source always. So batteries help us to use electricity without wires and electric sources.

Difference between Cell and Battery

       Cell is singular form of battery. Combinations of more than one cells connected in series are called as batteries.  Normally the voltage range for cell is from 1.2V to 3Volts while the range of voltage for batteries is not defined.  Normally 12 volts batteries are available for back up purposes but this voltage can be increase as much as you want. You can get the required output voltage by connecting batteries in series.

       In electrical circuits, there is a small difference between battery symbol and a cell symbol. Have a look on the picture below:

Difference between Batteries and cell
Figure 2: Difference between cell and Battery

Terms Related to Batteries

There are many terms related to batteries in the market and in the books enough to confuse you to understand the batteries. Here I will try to explain some of those terms in easy way:

What is Ah of Battery ?

        Ah of a battery simply telling you the amount of energy that a battery can store at a time. Here A is amps and h is hours. For example if 7Ah is written on a battery then it means it can deliver 7 amps for an hour. Of course nothing in this world is ideal so this hour will be cut off with respect to the battery you are using. Some type of batteries will give you 7 amps for 55 minutes and other will give you for 30 minutes. Nevertheless it’s a rough estimate.

What are Volts of Battery?

       This question seems silly but still there are a lot of things to learn here. Rated Voltage of battery is that voltage which battery provides at its terminal but the question is when? For example a 12 volt discharged battery is present in your hand and someone is asking you what voltage should be here on its terminals? You will say of course 12 volts!! Wrong!! It would be less than11.3 volts present on its terminals. Now what would be the voltage of charged voltage? It would be 12.7 volts. So clearly by this example you can understand the voltage of a battery is not a constant thing and you can calculate the charge present in the battery by measuring the voltage of a battery.

State of Charge of Battery

State of charge is basically the indication of charges present in the battery i.e. how much charging is remaining in the battery. There are lots of ways to measure the state of charge of a battery.

Self Discharge of Battery:

Rechargeable batteries cannot store their charges forever. They discharge slowly with respect to time even if they are completely disconnected from load. Some batteries discharges rapidly after charging and some discharges slowly depend on the type of the battery. This discharging of rechargeable batteries without load is called as self discharge of batteries.

Note: I did not say batteries instead I said “rechargeable batteries” because non rechargeable batteries can store the charges as long that one can say

“Non rechargeable batteries can store charges for forever”

Types of Batteries:

There are major two types of batteries which are as follows:

Rechargeable batteries:

As name suggests, Rechargeable batteries  are those which you can recharge after use.

Note: Recharging of batteries is not an ideal case. That’s why you have to change the battery after some years no matter which kind of battery are you using.

Some major types of rechargeable batteries:

  • Nickel Cadmium (NiCad) battery
  • Nickel Metal Hydride (NiMH) battery
  • Lead Acid Battery
  • Lithium Ion Battery
Rechargeable Batteries
Figure 3 : Rechargeable Batteries

Non Rechargeable batteries:

Some major types of non rechargeable batteries:

  • Zinc Carbon batteries
  • Alkaline batteries
  • Lithium batteries
Non-Rechargeable Batteries
Figure 4 : Non-Rechargeable Batteries/Cell

This is enough for basics of batteries. If you want to study about Non Rechargeable batteries and rechargeable batteries then click the links below:

If you want to know about how to make a complete automatic charger then click the link below:

Automatic Battery Charger

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