Series & Parallel Battery Connections

You’ve probably heard the terms “series” and “parallel” before. What do these terms mean and how do they influence what charger you need? When discussing batteries that are connected in either series or parallel, it is important to take into consideration the proper charger select that should be made when charging your battery.

Series Connection

To make a series connection between batteries, use a jumper wire between the negative of the first battery and the positive of the second battery. Run your positive wire off of the open connector from the first battery and your negative off of the open connector on your second battery.

In a series connection, the individual battery voltages are added together. When charging your battery, it is necessary to account for the total voltage of the string.

For example, if you have (2) 100 amp hour, 6 volt batteries connected in series, the total voltage is 12 volts and the amp hour capacity of the assembly is 100. In this situation, you would use a charger that satisfies both 12 volts and 100 amp hours. Electric golf carts often use 6V, 8V, or 12V batteries connected in series to produce a total of 36 or 48 volts.

Parallel Connection

A parallel connection is made by connecting the positives of all the batteries in the string down the line with a jumper wire, and then doing so with all the negatives. Then, connect the last positive and negative to the application.

Batteries connected in parallel increase the amp-hour capacity of the assembly, but not the voltage. A parallel battery system’s voltage is the same as the individual batteries, but it will increase the run-time for which it could power an item.

When charging batteries that are connected in parallel, it is crucial to take into account the increased amp-hour capacity when selecting your charger. A good example of a parallel connection is diesel pickup truck with (2) starting batteries connected in parallel to maintain 12 volts, but double the available starting amps and reserve capacity.


Whether it is the increase in voltage from a series connection or the increased amp-hour capacity from a parallel connection, understanding how these are different and the appropriate manner of charging your battery system is important in maximizing battery life and performance.