What is a battery bank? No, battery banks are not some financial battery establishments.A battery bank is connecting two or more batteries together for a single application. You might ask, what does this accomplish? By linking batteries together, you can increase the voltage, capacity (AH / Wh), or both.
When you need more power, you can construct a battery bank using widely available batteries. For instance, using a common group-size battery such as a group 24, group 27, group 31, or golf cart GC2 group size is much more affordablethan purchasing a heavy group 4D or 8D battery for your RV, camper, trailer, or boat.
The first thing you need to know is that there are three primary ways to successfully connect batteries: The first is via a series connection, the second is called a parallel connection, and the third option is a combination of the two called a series-parallel connection.
- How to wire batteries in Series
- How to wire batteries in Parallel
- How to wire batteries in Series-Parallel
How to wire batteries in series:
To connect batteries in a series, use a jumper wire to connect the first battery's negative terminal to the second battery's positive terminal. This leaves you a positive terminal on the first battery and a negative one on the second battery to use for your application.
When connecting batteries: Never cross the remaining open positive and negative terminals with each other, as this will short-circuit the batteries and cause damage or injury.
Be sure the batteries you're connecting have the same voltage and capacity rating and are of the same batch. Otherwise, you may end up with charging problems and shortened battery life.
How to wire batteries in parallel:
To join batteries in parallel, use a jumper wire to connect positive terminals together, and another jumper wire to connect negative terminals together. This establishes negatives to negatives and positives to positives. You CAN connect your load to ONE of the batteries, which will drain both equally. However, the preferred method for keeping the batteries equalized is connecting to the positive at one end of the battery pack and the negative at the other end.
How to wire in a series-parallel configuration:
If you have two sets of batteries connected in series, you can wire both sets into a parallel connection to make a series-parallel battery bank. In the images below we will walk you through the steps to create a 24 volts 70 AH battery pack.
Don't get lost now. Remember, electricity flows through parallel or series connections as if it were a single battery. It can't tell the difference.
Therefore, you can parallel two sets of batteries that are in series to create a series-parallel setup.
Creating a series-parallel battery bank:
Step 1 - Series First
First, we recommend putting each set in series first. To do this, you will use a jumper between the inner positive and negative terminals of each set to increase the voltage, as seen in the picture below: 
Step 2 - Parallel Each Series Set:
Once each set has been put in series, you can use jumpers to parallel each set together. Basically, the outer positives to positives and outer negatives to negatives, as seen in the final picture below:
In other words, there is no right or wrong method. However, most customers prefer to put their batteries in series first because it allows them to use onboard desulfators more effectively to extend battery life.
Don’t be concerned if a terminal has more than one cable connected to it. It's necessary to construct these kinds of battery banks successfully.
In theory, you can connect as many batteries as you want. But when you start constructing a tangled mess of batteries and cables, it can be very confusing, and confusion can be dangerous. Keep in mind the requirements for your application, and stick to them. Also, use batteries of the same capabilities. Avoid mixing and matching battery sizes wherever possible.
Always remember to be safe and keep track of your connections. If it helps, make a diagram of your battery banks before attempting to construct them. Good luck!
Quick Vocabulary Reference:
AMP Hour is a unit of measure for a battery's electrical storage capacity. A manufacturer will subject the battery to a specific amp draw over a 20 hour timeframe in order to determine the AH capacity. The amp/hr rating can significantly change based on the given load applied for more information see our article: Peukert’s Law | A Nerd’s Attempt to Explain Battery Capacity.
Voltage represents the pressure of electricity. Some applications require more "pressure," meaning higher voltage.
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Battery Banks
A battery bank refers to the connection of two or more batteries for a single application. This configuration allows for increased voltage, capacity (AH/Wh), or both. By linking batteries together, you can create a more affordable alternative to purchasing a single, heavy-duty battery for your RV, camper, trailer, or boat.
Connecting Batteries: Series, Parallel, and Series-Parallel Connections
There are three primary ways to connect batteries: series, parallel, and series-parallel connections.
1. Series Connection: Connecting batteries in series adds the voltage of the two batteries while keeping the same AH rating. For example, if you wire two 12-volt batteries in series, you will have a total voltage of 24 volts, but the total capacity (AH) remains the same. To connect batteries in series, use a jumper wire to connect the negative terminal of the first battery to the positive terminal of the second battery. This leaves a positive terminal on the first battery and a negative terminal on the second battery for your application. It is important to avoid crossing the remaining open positive and negative terminals, as this can cause short-circuiting and damage .
2. Parallel Connection: Parallel connections increase the capacity rating (AH) while keeping the voltage the same. For example, if you connect two 12-volt batteries in parallel, you will still have a total voltage of 12 volts, but the total capacity (AH) will increase. To join batteries in parallel, use a jumper wire to connect the positive terminals together and another jumper wire to connect the negative terminals together. This establishes a connection between the positives and negatives. You can connect your load to one of the batteries, which will drain both equally. However, it is recommended to connect the load to the positive at one end of the battery pack and the negative at the other end to keep the batteries equalized .
3. Series-Parallel Connection: If you have two sets of batteries connected in series, you can wire both sets into a parallel connection to create a series-parallel battery bank. This configuration allows for increased voltage and capacity. To create a series-parallel battery bank, first put each set in series by using a jumper between the inner positive and negative terminals of each set. Then, use jumpers to parallel each set together by connecting the outer positives to positives and outer negatives to negatives.
It's important to note that when constructing battery banks, you should ensure that the batteries have the same voltage and capacity rating and are of the same batch. Mixing and matching battery sizes should be avoided whenever possible. Additionally, keeping track of connections and following safety guidelines is crucial. Creating a diagram of your battery banks before construction can be helpful.
I hope this information helps you understand battery banks and how to connect batteries in different configurations. If you have any further questions, feel free to ask!
