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, follow our essential guide.
How To Connect Lithium Batteries In Parallel
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.
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.
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.
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.
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.
Be careful not to reverse connect the Positive and Negative.
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.
The Difference Between Lithium Battery Brands In Parallel
Enerdrive supports running its B-TEC batteries lithium batteries in parallel. It recommends a maximum battery bank size of two lithium batteries of equal voltage and amperage. For example, you can connect two 200Ah lithium batteries in parallel.
Invicta goes to two better than Enerdrive, allowing 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.
The Victron LiFePO4 Lithium Battery Smart range can be paralleled up to 5 batteries. This massively increases your discharge current AND deep cycle storage.
If you paralleled 3 x Victron LiFePO4 Lithium Battery 12.8V/200Ah-a, you would have a recommended continuous discharge current of ≤600A . You could safely run a 6000W inverter from this set up. This is a huge capability and reserved for serious caravan and motorhome installations. Victron also boasts a large cycle life at various depths of discharge:
- 80% DoD 2500 cycles
- 70% DoD 3000 cycles
- 50% DoD 5000 cycles
Your battery will last longer than the competitors under the same conditions.
Victron Energy have closed the loop so all their “smart” products can be connected in the Victron Energy app. From here you can monitor performance and adjust settings to suit your needs!
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.