How to Build a Battery Bank for a Solar Panel System?

In previous articles, we have compared different battery types and Solar Panels. We have also covered choosing the suitable solar charge controller and recommended the Best inverter Chargers. 

This blog will go through a step-by-step guide for building a battery bank. And many essential factors that all solar panel owners need to consider.

First, do you even need a Battery Bank?

This question can not be answered with a definitive yes or no answer. Although the battery bank is valuable and beneficial, it is not always a must-have component in the system.

For example, in grid-tied systems, the grid works like a giant battery connected to solar panels. The grid provides the needed electricity when solar panels can not produce enough. 

In some places, energy production works both ways, called Net metering programs. In a net metering system, extra electricity will be transferred into the grid for incentives or credits in these programs.

In this case, where is a battery bank essential?

In almost all types of solar systems, there is a benefit to having a battery bank. Even if you participate in a net metering program, a hybrid solar battery bank will have many benefits.

At first, in these systems, the system will store excess electricity in the battery banks until the batteries are fully charged. Then you can transfer the extra electricity to the grid and make money from your solar panel system. In addition, when solar panels are not producing enough power, battery storage will provide the needed power. 

Furthermore, a battery power bank is essential when grid connection is non-existent or weak. In off-grid systems like Kanwata Outfitters, storing the extra production of solar energy in a battery backup system is crucial. Now that we have covered the importance of a battery bank let’s start building one!

Step 1: What kind of battery is better for you?

Before going into details, you need to decide between getting Lead-Acid or Lithium-ion batteries. There are advantages and benefits to using each type of battery. You can learn more about them in our blog post on "Best Batteries for your next project."

A lithium battery bank will be lighter and take less space with more Depth of discharge. However, lithium batteries are sensitive to charging in cold temperatures and must be kept in a warmer place.

On the other hand, Lead-Acid batteries do not need extra attention in colder times and are much cheaper. However, Lead-acid batteries are less efficient, with less than 50% efficiency. And have a life span of around five years, where Lithium batteries often last longer than 12-15 years.

Once you have decided on the Battery, we can move to the next step.

Step 2: What battery bank capacity do you need? 

We often recommend a battery capacity that provides at least 12-24 hours of autonomy. Autonomy in solar panel systems is required as a safety measure. Suppose solar panels fail to produce the needed power. The battery bank will provide you with at least 12-24 hours of uninterrupted electricity until the problem is resolved.

To calculate the required Battery bank capacity for 24 hours of autonomy. First, find how much power you consume each hour and then multiply this number by 24. Always make room for some error by multiplying the final number by 1.25, so the capacity is 25% higher.

Let's assume that the average off-grid household uses 15kWh of electricity. This number means that your parallel or series connection batteries must produce 15kWh. 

Step 3: How many Batteries do you need?

After deciding on the battery, you can calculate the nominal battery power by multiplying the battery voltage by its capacity. We will use this accessible energy to find how many connecting batteries are required to produce autonomous power.

Let’s look at the examples below:

A small off-grid house uses approximately 15 kWh a day. Using the power of each Relion 100Ah battery, we can use a battery bank of 10 to 15 batteries for 12 to 24 hours of autonomy. Also, you can use a battery with a higher capacity like Relion 200 or 300 Ah to use fewer batteries in your battery bank.

We recommend using batteries with higher capacity for larger off-grid systems such as lithium battery solution 12.88V - 271 Ah. These batteries can make a lighter and smaller battery bank with a higher accessible power.

Step 4: Assembly and install the Battery bank.

If you have decided to use Lithium batteries, it is best to keep them in a warmer place, where the batteries are safe from below zero temperatures. Otherwise, while using Lead-acid batteries, we usually recommend a place where battery acid spill wouldn’t cause damage to the building or surroundings.

Once you know which battery and exactly how many of them you need, you can start building your battery bank. A few additional components, like a BMV battery monitor for checking on battery status at all times and a Victron Energy Lynx distributor, are great additions to your battery bank. You can consult with one of our project managers. 

Step 5: How to connect the batteries in a power bank? Series vs Parallel

Connection batteries in series or parallel entirely depend on your usage and your required output. Connecting batteries in series from the Negative terminal of one battery to the positive terminal of another will result in higher voltage without changes in the amp-hour capacity of the system. On the other hand, connecting batteries in parallel will add up the amp-hour capacity without changing the voltage. 

Batteries must be of the same voltage when connecting in parallel and amp-hour when connecting in series. It is best to use the same battery when connecting in series or parallel batteries l for the best results.

Both Parallel and Series will provide similar run times; however, series connections can be considered more efficient due to higher voltage, which allows the transfer of electricity for longer distances with high voltage cables.

In conclusion

Battery, banks are not always a must-have part of your solar panel system, but getting well-made batteries would make a significant difference in your experience with solar energy. Battery banks are the only solution to building a genuinely off-grid solar panel system. Even in grid-tied systems, a battery bank will guarantee energy production by solar panels, even in a power outage from the grid connection.

You can contact us for further assistance at any step of the process. Here at Volts Energies, we can help you choose the correct battery for your project from the highest quality products such as Relion, Lithium Battery Solution and Battle Born Batteries.