Series vs. Parallel Connections Explained

Posted July 31, 2019

While researching lithium batteries, you’ve probably seen the terms series and parallel mentioned. We are frequently asked the questions like, "what’s the difference between series and parallel”, “can RELiON batteries be connected in series.” It can be confusing if you’re new to lithium batteries or batteries in general, but hopefully, we can help simplify it.

Let’s start at the beginning - your battery bank. The battery bank is the result of connecting two or more batteries together for a single application (i.e. a sailboat). What does joining more than one battery together accomplish? By connecting the batteries, you either increase the voltage or amp-hour capacity and sometimes both, ultimately allowing for more power and/or energy.

The first thing you need to know is there are two primary ways to successfully connect two or more batteries: The first is called a series connection and the second is called a parallel connection.

Series Connections

Series connections involve connecting 2 or more batteries together to increase the voltage of the battery system but keeps the same amp-hour rating. Keep in mind in series connections each battery needs to have the same voltage and capacity rating, or you can end up damaging the battery. To connect batteries in series, you connect the positive terminal of one battery to the negative of another until the desired voltage is achieved. When charging batteries in series, you need to utilize a charger that matches the system voltage. We recommend you charge each battery individually, with a multi-bank charger, to avoid an imbalance between batteries.

In the image below, there are two 12V batteries connected in series which turns this battery bank into a 24V system. You can also see that the bank still has a total capacity rating of 100 Ah.


Parallel Connections

Parallel connections involve connecting 2 or more batteries together to increase the amp-hour capacity of the battery bank, but your voltage stays the same. To connect batteries in parallel, the positive terminals are connected together via a cable and the negative terminals are connected together with another cable until you reach your desired capacity.

A parallel connection is not meant to allow your batteries to power anything above its standard voltage output, but rather increase the duration for which it could power equipment. It’s important to note that when charging batteries that are connected in parallel, the increased amp-hour capacity may require a longer charge time.

In the example below, we have two 12V batteries, but you see the amp-hours increase to 200 Ah.


Can RELiON Batteries Be Connected in Series or Parallel?

Our standard lithium batteries can be wired in either series or parallel based on what you’re trying to accomplish in your specific application. RELiON’s data sheets indicate the number of batteries that can be connected in series by model. We typically recommend a maximum of 4 batteries in parallel for our standard product, however, there may be exceptions that allow for more depending on your application.

When using RELiON’s lithium batteries, there are a few items to note, specific to our series:

· Our HP Series batteries can be connected in parallel only.

· Our InSight batteries can only be connected in parallel and allows for up to 10 batteries in parallel.

Whether you’re seeking an increase in voltage or amp-hour capacity it’s important to understand the difference between parallel and series configurations, and the effects they have on your battery bank’s performance. Knowing the differences between these parallel versus series configurations allows you to maximize your lithium battery’s life and overall performance.

Have more questions?
Visit our FAQs page for more commonly asked questions on lithium batteries.

Ready to purchase your next battery bank?
Check out our full line of lithium batteries.



  • Wilkin

    I currently have a golf cart using 6 - 8 volt batteries in series. It’s almost 4 years old and will need to be replaced soon. I am considering replacing them with your lithium batteries. What combinations of your batteries will best suit my needs? Also, will my current battery charger work on your batteries? Will there be warnings to tell me that my batteries are running low on power? Will your gauge work for my applications? Thank you.

  • RELiON

    @wilkin: We recommend our 48V InSight battery. What type of cart do you have? If Yamaha, we would recommend three batteries, if another brand, two should suffice. Your existing charger may work, but only (2) battery chargers have been approved presently. As such, we will include a FREE one with any purchase of two batteries or more. There are SOC (state of charge) indicators on the battery (LED lights) but they are not audible and would be under the seat. Yes, our Battery Indicator will work with these batteries.

    Let us know if you want to proceed. If so, I can put you in contact with Brad Green who is handling our direct efforts with this battery.

  • Jhon

    Thanks for making these concepts clear, guys at EP have also explained the concepts here: Connecting Batteries Together – Series, Parallel and Series/Parallel Combined
    Thanks for sharing

  • Christopher Allen

    It's been a long time since I was a Naval Electronics Technician, but I seem to recall that wiring batteries in Parallel first, then in Series (IE, wire together in parallel up to the desired amperage, then wiring those groups in series up to the desired voltage) produces a better balancing between the batteries, and thus will greatly extend the life of the batteries.

  • Pas

    how to you combine series and parallel conection

  • Venkata Su

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    0 votes
  • Towing Edmonton

    This is a great article. You have explained the difference between the two very clearly. I am sure that others will find this information helpful. Thanks for sharing!