Connecting Lithium Batteries In Parallel

Sometimes running with one battery isn't enough. Maybe you need to boost your battery bank capacity? Or increase the run time of appliances when off grid.

Good news! There are ways to connect lithium batteries in parallel to double capacity while keeping the voltage the same.

This means two 12V 120Ah batteries wired in parallel will give you only 12V. But increases capacity to 240Ah.

Connecting your lithium batteries in parallel requires some preparation to ensure you don't do any expensive damage.

Before you connect your batteries always consult the product manual to ensure parallel connection is suitable. Parallel configurations will vary between battery manufacturers. 

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Here Is A General Outline:

1. Charge Them Up

Before you start, make sure any batteries you're going to run in parallel have been fully charged individually by matched chargers.

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2. Check The Open Circuit Voltage

The Open Circuit Voltage (OCV) between each battery should not have a difference greater than <0.2V.
After charging, set them aside for 8 hours.

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3. Find The Right Connecting Cables

The cables you use to join your batteries together play an important part in the performance of your batteries. You need to make sure your cables are the right size (diameter) to carry the required current - they need to be the same size as your maximum requirement, typically matched to your inverter. So make them the same size or larger than your inverter cables.

They also need to be the right length for efficiency. Ideally, make sure your cables are as a short as possible and the batteries are close together.

To find the right cable size, use Enerdrive's handy Cable Chart.

Next, ensure that the cables between each battery are equal length. This connects the batteries with the same amount of cable resistance, so all batteries in the system are working together equally.

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4. Check The Main System Cables

Where are the main system cables connected to the battery bank? The system cables supplying the loads are usually connected to the battery that's easiest to access or first, which simply results in poor performance and service life.

These main system cables should be connected across the whole bank, to ensure the batteries are charged and discharged equally for optimal performance.

Again, make sure the main system cables and the cables joining the batteries together are big enough to handle the total system current. That means if you have a large battery charger or inverter, the cables should be capable of carrying potentially large currents from these devices, as well as your other loads.

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5. Connect The Batteries

Connect the Positive poles to each other and do the same with the Negative poles. Then, connect the Positive of the first battery and the Negative of the last battery to the system.

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Be careful not to reverse connect the Positive and Negative.

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6. Try To Avoid 100% Discharge

Once you connect lithium batteries in parallel, you need to charge and discharge it as a whole system, so try to avoid a 100% discharge. A battery monitor can help you with this, cutting off the loads at a safe level long before your battery is close to discharge. Most lithium batteries on the market will have an inbuilt battery management system which will prevent over discharge.

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The Difference Between Lithium Battery Brands In Parallel

Enerdrive:

Enerdrive supports running its B-TEC batteries lithium batteries in parallel. It recommends a maximum battery bank size of four lithium batteries of equal voltage and amperage. For example, you can connect two 200Ah lithium batteries in parallel.

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Invicta:

Invicta also allows up to 4 batteries in parallel. All Invicta lithium batteries can be configured into a parallel configuration, providing you meet the manufacturer's conditions. For example, Invicta advises that all batteries in the parallel configuration must have been fully charged individually by matched chargers.

Always check the manufacturer's conditions before you connect your batteries in parallel.

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Renogy:

Renogy entered the market with their exciting "Core" range of Lithium batteries with a 100Ah and 200Ah model available the configurations are versatile and extensive. 8 of these batteries can be connected in parallel, please note batteries of the same model and capacity are required. 

The "Core" series allows for parallel connection, series connection and a hybrid parallel-series connection.

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Any questions about connecting your lithium batteries in parallel? Contact our experts on 1300 400 122.

DISCLAIMER* Please note, this advice is general in nature and we strongly recommend consulting the product manual and where relevant, a professional installer.