Dangers of Wiring batteries in series & parallel

If you want to purchase batteries, you have probably already done some research. While doing so, you have probably encountered terms like series or parallel. While these are simple words, their meaning is complex.


The biggest difference between wiring batteries in series and parallel is the output voltage of your setup. To minimize the potential danger of wiring batteries in parallel, you want to make sure voltage is distributed evenly across the batteries. To wire in series, each battery is connected to the next, whereas parallel battery wiring isn’t.

In this article, we’ll go more in-depth with the following:

  • How to do it right
  • How are amps affected?

Continue reading

Some people ask about the difference between series and parallel. Although they know what these words mean, they don’t know how they apply to the wiring. 

brand new batteries

These terms can confuse you if you are new to lithium batteries or even batteries in general. We are here to help you and teach you about the dangers of wiring batteries in series vs. parallel, and also show you how to do it.

Your battery bank is one of the most important aspects. When two or more are connected for a single application, it results in a battery bank.

If you increase it with more batteries, the voltage capacity also increases and allows you to generate more power. This connection is made through wiring, which is done in a parallel or series connection.

When you have multiple battery systems, it is essential to understand the difference between parallel wiring and series wiring. The performance and output of these will be determined by how you connect them. 

See below the differences between series wiring and parallel wiring in batteries. We will explain both of them, and you will be able to see how they perform and how efficient they are. 

Table of Contents

Dangers of connecting batteries in parallel

battery parallel series

Connecting batteries in parallel are not dangerous, and the risks are minimal. However, you should ensure that the voltage is distributed equally by both of your batteries. Both of them have the same life expectancy. 

It also depends on the way you use them. When you connect them in a parallel circuit, the voltage is equal, but the current increases. For some devices, this can be beneficial. For those that are sensitive without a protection circuit, it can be very dangerous for them.

There are 3 different dangers in connecting batteries in parallel:

  • Risk of explosion if the battery voltages are different
  • Primary batteries may leak or bulge
  • The lower voltage battery is more likely to overheat

For the health of your batteries, it is important to consider some aspects. Find information about their chemical construction and voltage, and capacity.

When you connect them in parallel, all of these specifications must be the same to provide the circuit with power efficiently. 

If you ignore these factors, working with such a system can be dangerous. You are exposed to the risk of injury and damaging your batteries and electronic devices. That is why the voltage and capacity of your batteries have to be the same. 

In the system, the better battery will charge the bad one. They will significantly affect their lifespan with this infinite loop of constantly charging and discharging themselves. In some extreme cases, this can generate a lot of heat and even start a fire. 

Series connections

These connections involve two or more connected batteries to increase the system’s voltage. While the voltage is increased, the amp-hour rating is stable and unchanged.

In the case of series connections, having all your batteries feature the same voltage and capacity rating is critical. If they are different from each other, you risk damaging them.

To connect your batteries in series, a positive terminal of one must be connected to the negative one. This way, the desired voltage can be achieved. Remember that you have to use chargers that match the system’s voltage.

We also recommend using a multi-bank charger. It will allow you to charge each battery individually and also avoid an imbalance between them. Explore the advantages and disadvantages of a series connection below.

Provides a higher system voltageYou can’t get lower voltages without a converter
Simple to understand and buildThe entire circuit will fall if one point in a series fails
All components carry the same currentThe circuit’s resistance grows as the number of components increases

Connecting batteries in series is ideal for larger applications that require high voltage output. Because the voltage is higher, you can use thinner wiring for a lower system current. Voltage drops will also be reduced significantly. 

A disadvantage of series connection is the lack of flexibility. All of your applications are required to work at a higher voltage.

If you connect two 12V batteries, you will get a system that produces 24V. Your 12V appliances cannot be supplied with power until you use a specific converter. 


In a parallel connection system, two or more batteries are connected. It’s done to increase the amp-hour capacity. It’s done while keeping the voltage at the same level. Positive terminals are connected through a cable. The same is done with negative terminals. 

You cannot power up anything above the standard voltage output with such a system. However, you can increase the time your equipment can be powered.

When connecting your batteries in a parallel connection, an increased amp-hour capacity might require a longer charging time. Take a look at the advantages and disadvantages of a parallel connection.

If one of the batteries fail, the other ones can still sustain the powerIt needs a large number of wires
Extended runtime with constant voltageThe voltage level will be lower and the current draw will increase

The main advantage of this connection is the increased capacity and longer applications of your system. If one malfunction, it won’t affect the others as they will continue to power up your appliances. 

The only inconvenience of a parallel system is a longer charge time. Voltage drops can also occur as the lower voltage means a higher current draw. Thick cables are also needed. Sometimes it can be difficult to power large applications. 

used car batteries

Connecting them in a series

When you connect them in a series, the voltage is added together while keeping the same amp-hour rating.

If you decide to join two 6-volt ones, your system will now produce 12 volts so you can power larger appliances. To connect them, use a jumper wire to connect a negative terminal to a positive one. 

When you connect batteries, do not cross the remaining open positive and open negative terminals.

This will result in a short circuit and damage the batteries. It also risks your safety, as this can lead to injury. When you work with batteries and electrical systems, you must take the necessary precautions.

All your batteries should be similar and have the same voltage and capacity. If they differ, you will face charging problems, and the lifespan will be significantly reduced. Here is a step-by-step instruction on how to connect them in a series. Follow them accordingly, and do not skip any step.

How to wire two batteries in series

  1. Connect a wire from the first battery’s negative terminal to the second one’s positive.

  2. Continue this connection for the rest of your batteries until they are connected in a line. This is your series.

  3. Use another wire to connect the positive terminal of your first battery with the positive terminal of the application you are trying to power up.

  4. Repeat the previous step. However, this time you will connect the last one’s negative terminal with your application’s negative terminal. 

After successfully following these steps, you should have a system of batteries connected in a series. You can also charge more batteries in this series, but you should also use a charger that can sustain the total voltage output. 

Depending on the manufacturer that produced them, it is important to know that not all of them are capable of connecting in a series. Read the instructions carefully and consult their manual for more information. 

Differences between the two methods

There are many differences between series and parallel designs. One of them is represented by the output voltage and the capacity of your system. Those wired in series will add together the voltages for an output of a total one. The parallel systems will have their capacity added together instead.

The total energy of both configurations is still the same. This energy is usually measured in amp-hours. For total available energy of 2,400 watt-hours, the series system will have two 12-volt batteries with a 100 Ah capacity each connected for a 24 volts output at a 100 Ah capacity. 

The parallel system will create 12 volts with a 200 Ah capacity. As you can see, the series system increased the voltage while the parallel ones increased the capacity.

Mixing voltages and capacities can damage your batteries. It is recommended to have them all similar to each other, with the same capacity and voltage specifications. 

high-capacity batteries

In series and parallel at the same time

You cannot simultaneously connect the same batteries in series and in parallel because it would result in a shortage of the system. But you can wire sets of batteries in series and parallel to create a larger system. 

When you connect them in parallel, you should have the proper jumper wire. For high Ah values, you will need thicker and bolder jumper wires.

It is necessary for connecting the battery to a safe environment. A thin wire will create problems using it for higher Ah values. 

To ensure your safety and the functionality of your battery system, it is important to take precautions and prevent unnecessary accidents. Because series and parallel connections have different functions, most people consider a combination between them to be the best option. 

Benefits of connecting your batteries in series and parallel at the same time include:

  • A significant increase in the voltage
  • An extended amount of runtime
  • Flexibility, allows you to form new connections

Eventually, it all comes down to your own needs. This combination can increase efficiency and functionality, but it should also be reliable and efficient for you. 

You can easily connect your batteries both in parallel and in series. It is done to increase both the voltage and amp-hour rating at the same time. This process is not complicated at all and can be done by anyone regardless of their electrical knowledge. 

When you purchase your batteries, make sure to check their specifications first. They have to share similar specifications, as not all can be connected in both series and parallel connections at the same time. Usually, the manufacturer will make this thing clear on the label. It makes it easy to find.

Although the process is easy, you can get it wrong if you do not follow the connection instructions correctly.

To prevent accidents, creating a system diagram is recommended and getting an idea of how connections will be made. You risk damaging your batteries and even injuring yourself if you get it wrong.

Seek the help of a specialist electrician if you are still unsure about connecting your batteries both in a series and parallel system. They will help you with advice and even give you specific advice for your electrical needs. 

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