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Is It Dangerous to Mix Battery Sizes? 

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When you’re building a battery bank for your mobile or off-grid application, it can be tempting to mix and match different battery sizes. Simply put, the answer is NO.

For the longer explanation on why this is a very bad idea, keep reading.

Mixing Battery Sizes: What Happens?

You cannot connect batteries of different amp-hours in series with good results.

We strongly recommend you DO NOT attempt to mix battery sizes (amp-hours) and connect together. Due to differences in battery management systems and battery cell counts, there may be a charging and voltage discrepancy between batteries.

This will cause the highest voltage battery to charge the lowest voltage battery attempting to create balance in the circuit. The greater the difference in voltage, the higher the probability of battery failure.

Can I Connect 100 Amp-Hour Battle Born Batteries to the 270 Amp-Hour Battle Born Batteries?

Here at Battle Born Batteries, we offer two different lithium battery sizes: our 100 Amp-Hour BB100 series and GC2 series, and the new 270 Amp-hour batteries.

These two different sizes of batteries should never be connected. Any attempt to connect Battle Born Batteries of different amp-hours will result in a voided warranty.

You should only ever connect batteries of the same size.

How Do I Connect Same Sized Batteries?

You may use two different types of connections for batteries of the same voltage and amp-hours together to make a larger bank. 

Proper Battery Connections

Parallel Connections – These connections are used when you want to increase the amperage of your battery bank. Most commonly, parallel-only connections are found in 12V systems.

The connections on this type of battery bank go from positive to positive and negative to negative.  Connecting this way will double your amps (see diagram below). 

Parallel Series Connection graphic
Parallel Connection


Series Connections – This type of connection is used when you need to increase the voltage of your battery bank. These types of battery connections are found in all types of battery banks including 12V, 24V, and 48V systems. 

For instance, making a connection to the positive and negative terminals in this orientation is different than a parallel connection. Doing so links the batteries together increases the voltage of the battery bank (see diagram below). 

Series Connection graphic
Series Connection


*If you plan to wire your batteries in series, please let us know when you place your order so we can make sure to match your capacity. 

Mixing Connections Vs. Mixing Battery Sizes

In some instances with a larger size battery bank, it is common to have series and parallel connections in your battery bank. 

However, you should never be connecting different battery sizes together in the same bank!

The Importance of a Reliable battery Management System

In line with the proper battery size for your system, a Battery Management System is another component of a well-managed and maintained lithium battery system. Lets take a look at what that looks like. 

A battery management system (BMS) is an electronic system that manages rechargeable batteries, including individual cells or battery packs. It ensures the battery operates within a safe area by monitoring its state, calculating secondary data, reporting it, controlling its environment, authenticating it, and balancing it.

What a BMS Does Graphic

How Does a Battery Management System (BMS) Work?

The individual cells within a battery pack are monitored by the battery management system to ensure safe operation. By calculating the current capacity of each cell, the BMS regulates the charging and discharging to void damaging the battery. Through current limits, the BMS prevents the battery from being overcharged or overdrawing the source and load. This protection ensures that cell voltages remain within a safe range, enhancing the battery’s longevity. 

The BMS also keeps track of the battery’s remaining charge by monitoring the energy flow and cell voltages in and out of the battery pack.  When the battery is depleted, the BMS automatically shuts it down. Unlike lead-acid batteries, lithium-ion batteries do not exhibit signs of degradation but simply turn off when the charge runs out. 

Built-In Safety Features

At Battle Born Batteries, our proprietary internal BMS system has three different levels. 

  1. The first level is 100 amps continuous, or 1200 watts at 12 volts. This means the battery can provide a continuous current of 100 amps until the battery is fully depleted. 
  1. The second level is 200 amps for 30  seconds (2400 watts at 12 volts). This level allows the batter to handle device surges of up to 2400 watts for a period of 30 seconds. 
  1. The third level is a ½ second surge up to the battery’s maximum capacity. If a high moment over 200 amps happens, the battery can handle it for ½ second. 

Our battery management system has a safety feature that continuously limits the current to 100 amps and will cut off any surge over 200 amps after half a second.

Six Battle Born Batteries Powering an RV

BMS and High Current Disconnects

If a current in the system exceeds a certain threshold, a Battle Born Battery will disconnect and attempt to reconnect after five seconds, vis the BMS. This safety feature protects the battery and informs the user that it is approaching its designed threshold. This is a huge benefit for batteries stored in hard-to-reach places, such as RVs and marine applications. In alignment with this, a BMS system is a requirement for marine applications according to new ABYC standards that have been ratified. 

Let us know if you have any additional questions about wiring or want to purchase more batteries for your system. Check out our website or give our sales and tech team a call at 855-292-2831.  

Want To Learn More About Electrical Systems and Lithium Batteries?

We know that building or upgrading an electrical system can be overwhelming, so we’re here to help. Our Reno, Nevada-based sales and customer service team is standing by at (855) 292-2831 to take your questions!

Also, join us on Facebook, Instagram, and YouTube to learn more about how lithium battery systems can power your lifestyle, see how others have built their systems, and gain the confidence to get out there and stay out there.

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20 thoughts on “Is It Dangerous to Mix Battery Sizes? 

  1. Hello. I am considering the purchase of your BB10012
    6 new units12v 100 ah
    I would like to have 24v 600ah in my RV
    Can this be done

  2. My other point other than that is
    If I connect my batteries in parallel, how can I connect the inverter terminals? and have maximum efficiency

    1. Hello Henry, that’s a great question. You want to connect the positive and negative from the inverter to opposite ends of your battery bank. This will allow for an even discharge across all batteries in your bank. Please let us know if you have any additional questions.

    1. Hi Darin, thanks for reaching out. Please keep the same battery models together in the bank and do not mix them.

      1. Nikki, I’m not sure I understand your answer. The two Battleborn batteries mentions in Darin’s question are both the same Ah rating and most likely age. Other Battleborn reps have responded that these are the same size batteries and can be mixed.

        Given that they can be mixed, can I add two of the other form factor (but “same” battery) batteries that are one year newer?

        1. Hi Dave! The BB10012 and BBGC2 batteries can be wired together in parallel (only) in the same battery bank. We do not recommend wiring the BB10012 and BBGC2 together in series. As far as the age of your batteries, you can add new batteries to your original Battle Born bank up to two years down the road without damaging, reducing lifespan, or harming them in any way.

  3. I am planning to get several Dragonfly 100 ah batteries with my Keystone SolarFlex system. I already have 4 Battleborn 100 ah batteries with a home backup system. Can the Battleborn batteries be added to the Dragonfly battery bank?

    1. Hi John. Yes you can. The batteries are the same size and have exactly the same chemistry in them.

  4. I read the above. Not explicitly stated are the specific compatibilities. Are the 270 Amp Hour GC3 and BB8D compatible in the same system? Series or Parallel? Same Cells, Same BMS, different form factor? Can BB8d be mounted in any orientation?

    1. Hi Dale! We recommend that you keep the battery models in your system consistent and don’t mix them. Yes, our batteries can be mounted in any position that is suitable to you.

  5. Is there a limit to how many batteries can be in parallel? If I insisted on a 12 volts system could I have… 18?
    With that many in paraellel is it still best to attach load to opposing ends? ( + on battery one and – battery 18)

    1. Hi Justin! There is no limit to how many batteries you can wire in parallel. The more batteries you add in a parallel circuit, the more capacity and longer runtime you will have available. With very large parallel battery banks comes much higher current availability as well. This means the proper system fusing is critical to prevent accidental shorts that could have catastrophic consequences with so much current available.

  6. I have 4 100 amp hour bb and want to add 4 more is it best to have them in parallel as one large bank or can I have 2 separate banks

    1. Hi Mark! There is no limit to how many batteries you can wire in parallel. The more batteries you add in a parallel circuit, the more capacity and longer runtime you will have available. Keep in mind that the more batteries you have in parallel, the longer it will take to charge the system.

  7. I have 1 GC3 270 ah and 1 100 ah bb battery. Both 12 volt. Both lithium. Can I connect them both in parallel?

    Can I connect them independently to the same Lynx power in?

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