how to connect 8 12v batteries to make 24v

You have 8 12V batteries, and you want to make a 24V battery?

Let me show you how.

Basics of connecting batteries in series and parallel

• Series connection adds up the voltage (V)
• Parallel connection add up the capacity (Ah)

• A series connection is made by connecting the positive (+) from one battery and the negative (-) of another battery.
• Parallel connections are made by connecting all the positives and negatives.

Connecting the batteries

There are many options for connecting 8 12V batteries to get a 24V battery.

It can become overwhelming, so I like to use a method of simplifying every connection that is made. Let me take you through my thought process.

Remember that series adds up the voltage and parallel adds the capacity?

We can do the following configurations:

• Connect 2 batteries in series to become 4 sets of 24V batteries, then connect these in parallel.
• Connect 4 batteries in parallel to become 2 sets of 12V batteries, then connect these in series.

Let’s start with the first:

2 batteries in series, then parallel

Let’s make four sets of two batteries in series. We do this by connecting two 12V batteries in series to become four sets of 24V batteries.

Now we have four sets of 24V batteries. We now need to connect these batteries in parallel.

We connect them in parallel by connecting all the positives (+) and negatives (-) together. We can do this with a busbar.

Make sure these wires are all the same length!

If these wires are not the same length, one battery will work harder than the other battery. (See principle of current sharing here)

If we connect these batteries in parallel, it looks like this:

It looks like a mess, but it’s very simple. Connect all four positives to a busbar and connect all four negatives to a busbar.

This is another configuration, but it comes down to the same. two batteries in series, and then paralleled together.

There you have it, the first configuration where we connect two batteries in series and then parallel connect.

Next, let’s look at 4 in parallel and then series.

4 batteries in parallel, then in series

We will now add 4 batteries in parallel and have the two sets connected in series.

We will connect all the positives and the negatives to become two big batteries of 12V.

Then we need to connect these two parallel sets in series to become the following configuration:

Which method do I recommend?

I recommend method one (two in series, then parallel) because you will have better current sharing.

1. Connect two batteries in series
2. Connect the remaining positives and negatives all together in parallel

It’s important to note that the wire length for the parallel connections are the same length.

If you want to know which batteries I recommend, read my expert article here.

Safety Precautions and Best Practices

When connecting eight 12V batteries to create a 24V battery system, it’s crucial to adhere to safety precautions and best practices to ensure optimal performance and prevent potential hazards. Here are some important guidelines to follow:

• Use appropriate cable sizes and connectors: Choose the correct cable sizes based on the current and distance between the batteries. Using cables that are too thin can result in voltage drop, overheating, and reduced system efficiency. Also, use high-quality connectors to ensure strong and safe connections.

• Inspect connections for any loose or corroded parts: Regularly check your battery connections to ensure they are tight and corrosion-free. Loose or corroded connections can lead to reduced performance, overheating, and fire hazards.

• Use batteries of the same type, capacity, and state of charge: Mixing batteries with different chemistries, capacities, or states of charge can result in an imbalanced system, potentially causing some batteries to overcharge or discharge too quickly. Always use identical batteries to maintain a stable and efficient battery bank.

• Regularly maintain and monitor the battery bank: Periodically inspect your battery bank for signs of wear, damage, or swelling, and keep the batteries clean and dry. Regular maintenance can help extend the life of your batteries and ensure optimal performance. In addition, consider investing in a battery monitoring system to track the state of charge and overall health of your battery bank.

• Use safety goggles when working on batteries. A wrong connection can create sparks which can damage your eyes.

• Use insulated tools when working on a battery. The consequences will be devastating when you drop a wrench on the battery posts. Therefore always insulate your tools with electrical tape or use designated insulated materials.

Following these safety precautions and best practices, you can create a reliable and efficient 24V battery system using eight 12V batteries. Always prioritize safety and proper maintenance to ensure the longevity and performance of your off-grid solar power setup.

 If you connect batteries in series, ensure they are at the same state of charge! Always use safety goggles and insulated tools when working with batteries!