Step-by-Step Guide: How To Connect Solar Panels To Battery In 7 Steps

Learn how to connect solar panels to battery bank in 7 easy steps.

Follow this step-by-step guide to discover how I connect solar panels to the solar battery(s) efficiently and safely.

Thousands of articles on the internet regarding how to connect solar panels to solar battery banks provide unclear instructions or leave out essential details.

Relying on incomplete advice may lead to improper connections, system inefficiencies, and added costs.

Solar power for home, business, or off-grid living is an extensive investment, and proper connections are essential to safeguard this investment.

That’s why in this post, you’ll learn how to connect your solar panels to a solar battery bank correctly in 7 easy steps:

1. Match solar panel voltage to battery voltage.
2. Use a charge controller.
3. Select proper solar cables, fuses/circuit breakers, and connectors.
4. Connect the solar battery bank to the solar charge controller.
5. Connect the solar charge controller to the solar panel output.
6. Configure your charge controller settings
7. Ensure secure connections and proper grounding.

Preparation

Gear Up: Assemble the Right Solar Energy Puzzle Pieces – Material and Tools.

Imagine a jigsaw puzzle – you need all the right interlocking pieces for the complete picture.

Solar energy systems are similar. Before jumping into wiring, get your ducks in a row.

So, what will you need to make this adventure a success:

Read The Ultimate Guide to Solar Power System Maintenance 2023 for more information about these tools. Most, if not all, of the tools used in solar power maintenance can be used when connecting solar panels to battery banks.

How To Connect Solar Panels To Solar Battery: The Key Points

In this article, I will describe connecting a Silfab Elite Mono 360W solar panel to a Renogy 100Ah Deep Cycle AGM Battery via a Victron Energy SmartSolar MPPT 150/70 solar charge controller rated for 150V and 70A. Therefore, the choice of solar cables and circuit breakers (or fuses) will depend on the wattage output of the 360W panel and the amperage capabilities of the 70A charge controller and 100Ah battery. Your system parameters may differ; however, based on the calculations I will provide, you can quickly adapt the wire and fuse sizing as needed.

Here are the steps to follow:

Step 1: Match voltages: panel to battery

When connecting solar panels to batteries, the very first thing to do is ensure the solar panel voltage matches the battery voltage.

This is crucial for proper charging and system performance.

For example, I’m using 380W Silfab solar panels with an open circuit voltage of 45.13V (in ideal conditions and about 42.36V in unideal conditions) and a 12V 100Wh Renogy deep cycle battery.

Note that you’ll get the best performance when the solar panel’s open circuit voltage (VOC) is 1.4 to 1.8 times the battery’s voltage.

My 380W Silfab solar panels have a VOC of 45.9V. So, it will charge my battery at 16.8 to 21.6 Volts.

1.4 x battery voltage = 16.8V OR 1.8 x battery voltage = 21.6V

To charge a 12V battery, you need at least 12.6V.

But thanks to the charge controller, this minor difference is no problem.

If the solar panel voltage is too high, it can damage the batteries by overcharging. If too low, the batteries may never fully charge.

The key is using a charge controller to convert the higher voltage panels to the proper level for the batteries.

Matching the voltages prevents damage and ensures efficient operation.

Taking the time to calculate voltage and select equipment properly gets your solar setup started right.

Read Solar Batteries: The Ultimate Guide to Solar Batteries and Solar Panels: The Ultimate Guide to Solar Panels

Step 2: Use a charge controller.

The second step is to use a charge controller to connect the solar panels to the batteries.

For smaller systems, a PWM controller works if sized properly.

The PWM controller should have a max input voltage rating above the solar panel’s VOC.

For example, the 30A PWM controller with a 60V max input rating exceeds the 45.13V VOC of my 380W Silfab panels.

In my case, I’m using an MPPT controller that can handle 70-150V, well above my panel’s VOC of 45.13V.

A simple PWM controller will protect your system. An MPPT controller will protect your system while maximizing the output of your solar panels.

Choose a controller sized appropriately for your actual panels’ and batteries’ specs. Closely checking the specs ensures compatibility.

Read Solar Charge Controller: Everything You Need To Know

Step 3: Choose cables, fuses, connectors

The third step is to select the right solar cables, fuses/circuit breakers, and connectors to link all the system components safely. 

For cables, 10 AWG wires work well for runs up to 10 feet in 12V systems like ours. 

Use copper cables for the best conductivity. 

Recommended fuses or circuit breakers are 1.56 times the short circuit current – so for our 380W panel, which has an 8.4A short circuit current (1.56 x 8.4A = 13.1A), use 15A fuses or breakers.

MC4 connectors are commonly used for the charge controller connections and make a secure, weatherproof link. 

Adding the proper overcurrent protection and high-quality connectors prevents hazards and power loss.

Take time to determine the proper size components for the current and voltage in your specific system.

Correct cabling and connections ensure all parts communicate efficiently.

Read Solar Wiring and Cables: Discover Everything You Need to Know

Step 4: Link battery bank to charge controller

The fourth step is connecting the solar battery bank to the charge controller. 

First, ensure the charge controller and batteries are powered off for safety. 

Locate the charge controller’s battery connection terminals, often labeled “Battery +” and “Battery —.” 

Double check polarity – positive + to positive + and negative — to negative —. 

Switch the controller on to begin regulation. 

Taking it slow helps avoid costly wiring mistakes during this crucial connection.

Step 5: Connect the controller to panel output

The fifth step is connecting the solar charge controller to the solar panel output. 

With all devices powered off, locate the charge controller’s solar input terminals, often labeled “Solar Panel +” and “Solar Panel —.” 

Check polarity again for accuracy. 

Once everything is securely connected, carefully switch on the controller to allow energy transfer from the panel to the battery bank through the controller.

Taking it slow during wiring helps prevent issues once the system is operational.

Step 6: Configure the Charge controller

Before operation, the charge controller must be configured to match your system and battery type.

For a PWM controller, key settings are battery type (i.e., Lithium Iron Phosphate (LIPO), lithium, iron phosphate, lead-acid, and Absorbent Glass Mat (AGM) batteries, etc.), charging voltages, and current limits. 

An MPPT controller adds settings like maximum power point tracking and multiple charging stages. 

When configuring either type:

• Select the correct battery chemistry and total capacity.
• Set proper absorb and float charging voltages.
• Enable temperature compensation if the sensor is installed.
• Limit maximum charging current to prevent overload.
• Activate MPPT tracking on MPPT controllers to maximize harvest.

Regardless of PWM or MPPT, customizing protects batteries and optimizes performance. 

Reference the manual and start conservatively. 

Proper configuration ensures the controller meets the needs of your specific components and setup.

Read Solar Charge Controller not Charging Battery: Causes and Solutions.

Step 7: Ensure secure connections and proper grounding.

The final step is verifying all connections are secure, properly grounded, and weatherproof. 

Use cable strain reliefs anywhere wires enter an enclosure to avoid loose connections from vibration or tension. 

Tighten all terminals to the torque specs in the manuals to prevent overheating. 

Ensure unused charge controller ports are sealed with rubber caps to prevent corrosion. 

Ground the system by connecting the battery bank negative to a copper rod driven into the earth, providing a safe path for stray current. 

Taking time to properly fasten and seal all connections and establish a good earth ground ensures your solar system operates safely and maintains performance through changing weather conditions.

Read The Ultimate Guide to Solar Power System Maintenance

What if I Have Two or More Batteries

When connecting two or more batteries in a solar system, the general procedure remains similar, but a few fundamental steps change.

Configure multiple batteries into a single battery bank by connecting them in series or parallel.

Use heavier gauge cables sized for the total bank amperage.

Fuse or breaker ratings must handle the entire bank’s current, not just a single battery’s.

Wire resistance can cause voltage differences with more batteries, so ensure robust interconnections.

Add termination bars as needed to consolidate connections to the charge controller or inverter.

Multiple batteries also require more maintenance and space, so plan accordingly.

However, following the same systematic process for a larger battery bank allows your solar system to store additional power.

Safety Precautions

Prioritizing safety throughout the process of connecting your solar panels to a battery is of paramount importance.

Reversing polarity or mismatching voltages can lead to disastrous results.

For example, accidentally connecting the positive and negative cables backward from the solar panel or the battery to the charge controller can instantly fry the charge controller due to reversed polarity. 

Always double-check wiring diagrams to avoid this mistake. 

Likewise, if the solar panel voltage doesn’t match the input rating on the charge controller, it could get overloaded and become damaged – if the output is too high.

Another risk is using undersized cables that can’t handle the system amperage. The cables may overheat, melt, and cause a fire hazard. 

Selecting the right gauge cables for the expected amperage is crucial. Skimping on cheap connectors that aren’t rated for outdoor use also asks for trouble down the road.

Before making any connections, use a voltmeter to verify that the solar panels and battery bank are disconnected and powerless. 

Always follow the manufacturer’s instructions exactly as stated. 

Lastly, only work in dry conditions and never take shortcuts. It may be tempting to solder wires in damp weather or skip installing fuses, but violating safety codes and best practices often leads to preventable problems. 

Taking the time to do the job correctly will prevent headaches and costs in the long run.

How to Connect Solar Panels to Battery: Final Thoughts

As you can see, connecting a solar panel to a battery bank is pretty straightforward.

Matching your solar panel and solar battery voltages and selecting the right cables and components can be tricky.

Ultimately, a proper solar panel to solar battery connection comes down to following instructions and ensuring you select the right components. Also, never forget the charge controller to avoid overcharging the battery.

Because that is how you ensure safe and secure connections – following instructions.

To recap, the seven steps are:

• Match voltages: panel to battery.
• Use a charge controller.
• Choose cables, fuses, connectors.
• Link battery bank to charge controller.
• Connect the controller to the panel output.
• Configure charge controller settings.
• Ensure secure, grounded connections.

While this process can be doubting, following these seven steps will make it easier.

Now it is your turn to get a solar panel, a charge controller, a solar battery, cables, fuses, connectors, and practice.