How to connect batteries in series or in parallel

2019-01-09 08:54:00

What is a bank of batteries? No, it's not some kind of financial battery establishment. A battery bank is the result of joining two or more batteries together for a single application. What does this accomplish? Well, by connecting batteries, you can increase the voltage, amperage, or both. Finally an illustrated description of what it means to connect batteries in series or parallel.

We frequently get asked the question, "How am I supposed to connect my battery if I want to double the capacity but not the voltage?", or similar questions. It can be confusing if you've never done it, but hopefully this'll make it simpler. Be sure to read the important notes at the bottom to protect yourself from damaging any equipment! 

Connecting in Series

The first thing you need to know is that there are two primary ways to successfully connect two or more batteries: The first is via a series and the second is called parallel. Let’s start with the series method.A series connection adds the voltage of the two batteries, but it keeps the same amperage rating (also known as Amp Hours). When connecting your batteries in Series you are doubling the voltage while maintaining the same capacity rating (amp hours).Just use a jumper wire between the negative of the first battery and the positive of the second battery. Run your negative wire off of the open connector from the first battery and your positive off of the open connector on your second battery. 

For example, these two 6-volt batteries joined in series now produce 12 volts, but they still have a total capacity of 10 amps.

Batteries joined in a series

6 Volts Batteries joined in a series 12 Volts

To connect batteries in a series, use jumper wire to connect the negative terminal of the first battery to the positive terminal of the second battery. Use another set of cables to connect the open positive and negative terminals to your application.

Note: Never cross the remaining open positive and open 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. Otherwise, you may end up with charging problems, and shortened battery life.

Connecting in Parallel

The other type of connection is parallel. Parallel connections will increase your current rating, but the voltage will stay the same. In the “Parallel” diagram, we're back to 6 volts, but the amps increase to 20 AH. It's important to note that because the amperage of the batteries increased, you may need a heavier-duty cable to keep the cables from burning out.

When connecting in Parallel you are doubling the capacity (amp hours) of the battery while maintaining the voltage of one of the individual batteries. This would be used in applications such as laptop batteries, some scooters, some ups backups, etc. Use a jumper wire between the positives of both batteries and another jumper wire between the negatives of both batteries. Connect your positive and negative wires to the same battery to run to your application. 

Batteries joined in a parallel

6 Volts Batteries joined in a parallel

To join batteries in parallel, use a jumper wire to connect both the positive terminals, and another jumper wire to connect both the negative terminals of both batteries to each other. Negative to negative and positive to positive. You CAN connect your load to ONE of the batteries, and it will drain both equally. However, the preferred method for keeping the batteries equalized is to connect to the positive at one end of the battery pack, and the negative at the other end of the pack.

Important notes: When connecting batteries in a pack there are some important things to keep in mind - - Find out the requirements of your application. For example: Don't double the capacity on your Power Wheels vehicle if you're not supposed to...you could burn up the engine. Follow the recommended guidelines for your application. - Don't use two different chemistries when connecting a pack. Usually the voltages will be different, but more importantly the charge rates will be different and the capacities may be different, thus resulting in a shortened life span. - Try to match capacities as much as possible. When connecting batteries in a pack you should try to match the capacities as much as possible to avoid discharging one battery quicker than another. A pack operates at a combined voltage so your one cell that discharges quicker will likely discharge deeper than it may be able to recover from. 

Connecting in Series and Parallel

Batteries equalized is to connect to the positive at one end of the battery pack, and the negative at the other end of the pack.It is also possible to connect batteries in what is called a series/parallel configuration This may sound confusing, but we will explain below. This is the way you can increase your voltage output and Amp/Hour rating. To do this successfully, you need at least 4 batteries.

Batteries joined in series and parallel

6 Volts Batteries joined in series and parallel 

If you have two sets of batteries already connected in parallel, you can join them together to form a series. In the diagram above, we have a bank that produces 12 volts and has 20 amp hours.

Don't get lost now. Remember, electricity flows through a parallel connection just the same as it does in a single battery. It can't tell the difference. Therefore, you can connect two parallel connections in a series as you would two batteries. Only one cable is needed; a bridge between a positive terminal from one parallel bank to a negative terminal from the other parallel bank.

It's alright if a terminal has more than one cable connected to it. It's necessary to successfully construct these kinds of battery banks.

In theory, you can connect as many batteries together as you want. But when you start to construct 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.

Choose a More Powerful Battery

Quick Vocabulary Reference:

AMP Hour is a unit of measure for a battery's electrical storage capacity. The standard rating is an amp rating taken for 20 Hours.

Voltage represents the pressure of electricity. Some applications require more "pressure," meaning higher voltage.

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