How-To Guide: Connect Batteries in Series or Parallel

Power - by Joe Weber - updated on 10/30/2023

Depending on the circumstance, you may need to connect your batteries to one another. Use this handy step-by-step guide if you need to connect your batteries in series, parallel or series-parallel.

A great example of an application that uses series connections is a golf cart. Golf carts typically have multiple batteries wired in series to create the 24, 36 or 48-volt system required.

Why Would You Connect Batteries Together?

There are three different ways to connect batteries together, each with its own outcome.

1. Connect in series - Connecting two or more batteries together in series will increase the overall voltage. For example, if you connect two 12V 75Ah batteries in series, you will have a battery voltage of 24V and a capacity of 75Ah.

   Batteries connected in series must have the same voltage and capacity ratings.

2. Connect in parallel - Connecting two or more batteries together in parallel will increase the overall capacity. For example, if you connect two 12V 90Ah batteries in parallel, you will have a battery voltage of 12V and a capacity of 180Ah.

   Batteries connected in parallel must have the same voltage rating and it is recommended to use batteries of equal capacity.

3. Connect in series and parallel - You cannot connect each battery in both series and parallel at the same time but you can have sets of batteries connected in series where the sets are connected in parallel.

   Connecting two or more sets of batteries together by wiring them in a series-parallel connection will increase both the voltage and capacity of the battery bank. For example, if you have 6V 215Ah batteries in a series-parallel connection, you can end up with a battery voltage of 12V and 645Ah.

   Batteries connected in series and parallel must have the same voltage and capacity ratings.

Note

Batteries connected in any of these configurations must have the same battery chemistry. You can only connect lead-acid to lead-acid, LiFePO4 to LiFePO4, etc.

How to Connect Batteries in Series

To connect batteries in series to increase the voltage you must first double-check that your batteries are the same voltage and capacity. Using batteries with different voltages could result in damaged batteries.

1. Connect the negative terminal of one battery to the positive terminal of the other battery with battery-to-battery cables.
   1. Continue this until all the batteries are connected.
2. Connect the negative terminal of the first battery to the application.
3. Connect the positive terminal of the end battery to the application.

How to Connect Batteries in Parallel

In order to be connected in parallel be sure to check that the batteries are the same voltage. It's best to use batteries with the same capacity as well.

1. Connect the negative terminal of the first battery to the negative terminal of the next battery. Continue until all of the batteries are connected.
2. Connect the positive terminal of the first battery to the positive terminal of the next battery. Continue until all of the batteries are connected.
3. Connect the positive and negative terminals of the end battery to the application.

How to Connect Batteries in Series-Parallel

When connecting sets of batteries in a series-parallel connection to increase the voltage and capacity you must first double-check that your batteries that are connected in series are all the same voltage and amp-hour capacity.

1. Align your batteries so they are in the correct position for your application.
2. Start by wiring sets of batteries in series.
   1. Connect the negative terminal of one battery to the positive terminal of the other battery with battery-to-battery cables.
   2. Continue this process until all battery pairs are connected.
3. Connect the negative terminal of the first series battery pair to the negative terminal of the battery pair next to it. Continue until all of the series pairs are connected on the negative side.
4. Connect the positive terminal of the first series battery pair to the positive terminal of the battery pair next to it. Continue until all of the series pairs are connected on the positive side.
5. Connect the positive and negative terminals of the end battery to the application.

What Batteries Can I Connect in Series or Parallel?

Sealed Lead Acid is the most common type of battery that is connected in series or parallel. You will find many Campers & RVs, golf carts as well as boats with battery banks that are wired this way.

Lithium batteries, like our X2Power LiFePO4 deep-cycle batteries, can also be connected in series and parallel but you need to pay attention to the battery management system parameters and specified limits when doing this.

Should I Replace All Of My Batteries at the Same Time?

As a best practice, you should replace all batteries at the same time when you have batteries in series or parallel connections. Believe it or not, replacing all of the batteries at the same time will save you time and money in the long run.

If you suspect that your multi-battery system might be on its last legs, bring your batteries to your local Batteries Plus to have our battery experts test your batteries, free of charge. If your batteries do need to be replaced, we have a large selection of batteries from brands like Duracell Ultra and X2Power to get your equipment working its best again.