how to connect two 12 volt batteries in parallel

How to Connect Two 12 Volt Batteries in Parallel:

A Comprehensive Guide:

Connecting two 12 volt batteries in parallel is a common solution for those looking to increase the capacity of their battery system without altering the voltage. This setup is especially popular in applications requiring extended battery life, such as in RVs, marine applications, solar power systems, and off-grid energy storage. This detailed guide will walk you through each step of connecting your batteries in parallel, discuss the advantages, and explain how Himax Electronics can enhance your setup.


Understanding the Basics of Battery Connections

When batteries are connected in parallel, the positive terminals are connected to each other, and the same is done with the negative terminals. This type of connection keeps the voltage the same but increases the overall ampere-hour (Ah) capacity. Here’s what you need to know:


Voltage: The voltage of the battery setup remains the same as one battery. If each battery is 12 volts, the parallel system will also be 12 volts.

Capacity: The capacities of each battery are added together. If each battery has a capacity of 100 Ah, the total capacity of the parallel system would be 200 Ah.

Advantages of Parallel Connections

Connecting batteries in parallel has several benefits:

Increased Capacity: More capacity means more energy storage, allowing for longer usage times between charges.

Redundancy: If one battery fails, the system can continue to operate on the remaining battery, which is crucial in critical applications.

Flexibility: Adding more batteries in parallel is a scalable solution that can be tailored to meet specific energy requirements.

To Connecting Two 12 Volt Batteries in Parallel

Step-by-Step Guide:

Here’s how to safely connect two 12-volt batteries in parallel:


Select Compatible Batteries: Ensure the batteries are of the same make brand, model, voltag, capacity, and roughly the same age and usage level.

Gather Materials: You’ll need suitable gauge cables, wrenches, wire brushes for cleaning terminals, insulated gloves, multimeter, and corrosion-resistant spray or grease.


Turn Off Power: Disconnect all loads from the battery.

Clean the terminals: Use a wire brush to clean the battery terminals, making sure to use the same size and length of wires.

The max connection in parallel is: no more than 10 pcs. Before connecting in parallel, fully charge the battery and test the voltage of each battery. It is recommended to control the battery voltage difference ≤ 20mV to extend the battery life.

Connect Positive Terminals: Use a cable to connect the positive terminal of the first battery to the positive terminal of the second battery.

Connect Negative Terminals: Similarly, connect the negative terminals (as shown in the picture).

Secure Connections: Tighten all connections with a wrench to ensure they are secure and apply corrosion-resistant spray or grease to prevent corrosion.

Testing and Activation:

Check the Connections: Double-check all connections to ensure they are tight and correctly configured.

Test with a Multimeter: Use a multimeter to check the voltage across the battery setup. It should read the same as one of the single batteries if connected correctly.

Power On: Turn on your system and monitor the initial performance to ensure everything is working as expected.

Safety Considerations and Maintenance

Regular Monitoring: Check the battery voltage and connections regularly to ensure there are no signs of corrosion or loose connections.

Equal Charge Levels: Always connect new batteries with similar charge levels to avoid imbalances.

Maintenance Checks: Regularly conduct detailed checks to ensure the batteries are functioning correctly and safely.

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The Himax Electronics Advantage

Partnering with Himax Electronics for your battery needs comes with significant benefits:

Quality and Reliability: Our 12-volt batteries are designed for high performance and reliability, ensuring they work perfectly in parallel configurations.

Expert Support: Himax Electronics provides expert guidance and support to help you design and implement the most effective and safe battery systems.

Custom Solutions: We offer customized battery solutions tailored to meet the specific requirements of your applications, whether for leisure, work, or critical backup systems.


Connecting two 12-volt batteries in parallel is an effective way to increase your system’s capacity and ensure longer operational times. With the right approach and adherence to safety practices, this setup can significantly enhance the efficiency and reliability of your energy system. Choosing Himax Electronics as your battery supplier ensures that you get not only top-quality products but also comprehensive support to make the most of your energy solutions. For more information about our products and services, visit Himax Electronics online or contact our customer service team today.