Batteries can be connected in series or parallel or both in order to achieve different aims.When batteries are connected either in series or in parallel or both for a single application, it is called a battery bank. Well, when batteries are connected, it can increase the voltage or amperage, or both. This is useful when you need more power, instead of getting a massive battery of high voltage or amperage,you can construct a battery bank.
Firstly, you need to know that there are 3 ways to connect two or more batteries. They are:
Series Battery Connection
Batteries connected in series increases the total output voltage but the amperage rating (also known as Amp Hours) remains the same. For example, if two batteries rated 3 Volts are connected in series, it will produce 6 Volts but the amperage rating remains the same.
In order to connect batteries in series, connect the negative terminal of the first battery to the positive terminal of the second battery. Then, connect the open positive and negative terminals to your application or device.
Note: Never cross the open positive and open negative terminals to each other ), this will cause damage to the batteries or may cause injury to you. The total output voltage of batteries connected in series is the sum of the individual battery that makes the connection.
It is ideal to be sure that the batteries,you are connecting have the same voltage and capacity rating. Otherwise, this might lead to charging problems, and shortening of battery life. You will see this type of connection in laptop battery.
Parallel Battery Connection
Parallel battery connection is used when higher current and long run time is required. The total current that will be delivered by the batteries in parallel will the sum of all the currents produced by each battery. You may need heavier duty cable/wire to elude the cables/wires from burning out due to increase in the amperage of the batteries.
In parallel connection of batteries, all the positive terminals are joined to one point and all the negative terminals are joined to another point. Then the load can be connected to one of the batteries, but both drain equally. Parallel battery connection are found in power bank, the more batteries are in parallel, the more the mAh.
Series-Parallel Battery Connection
This type of connection is done when increase in voltage output and current rating are needed. To do this, more than two batteries are needed (at least 4 batteries). If you have two sets of batteries already connected in series, you can join them together to form a parallel. Therefore, you can connect two series connections in parallel as you would for two batteries. This type of battery connection can be found in laptop battery. Theoretically, you can connect as many batteries together as you want.