Mixed Panels

How Connecting Different Solar Panels or Adding New Ones Affects Your System

• Introduction
• Mixing Panels
• The Scenario
• Why Mixing Solar Panels Happens and What to Consider
• Strategies for Successfully Mixing Panels
• Conclusion

Introduction

I often visit locations with very old solar panels, some of which seem like relics from another era. They often have an unusual appearance, and it's common to find just one or two panels, occasionally three if you're lucky. These panels are typically over 15 years old, sitting on rooftops as 12-volt systems. They were very expensive in their day and it is why there are only one or two them. If a second panel was added, it was likely installed a decade ago when it was considered the latest technology, but now it too is outdated. These setups are usually the easiest to address: simply replace them with more affordable, modern 24-volt panels that are five times more powerful.

Then there are situations involving solar panels that are only 3 to 5 years old. Five years ago, these panels were fairly decent, but now they may not meet current standards or expectations. In such cases, we face a decision: either find a way to integrate and continue using these panels, or consider selling them and upgrading to brand-new ones. What is the best approach in these scenarios?

While this article primarily focuses on off-grid setups, similar challenges can arise in grid-tied systems when expanding or replacing panels. Grid-tied systems also require careful consideration of panel compatibility, inverter or microinverter capacity, and overall system design to ensure seamless integration, optimal performance, and long-term efficiency.

Mixing Panels

As solar technology continues to grow in popularity, many homeowners and businesses look to expand their existing solar installations. However, adding new solar panels or mixing different types of panels in a single system is not as simple as it may seem. Understanding how mixed panels interact and how they can affect your system’s performance is crucial for making informed decisions. In todays newsletter, we will explore the impact of connecting different solar panels, the challenges it presents, and strategies to optimize your system when upgrading or expanding.

If I came across a system with a mix of older panels, where one was added to increase power due to lower prices years ago, and connected was two 12-volt solar panels, one being a 100-watt panel with a 5-amp output and the other a 150-watt panel with an 8-amp output, what would the total output be in watts and amps for both parallel and series configurations?

If you connect the two panels in parallel, the voltage stays at 12 volts, but their currents combine, giving you a total of 13 amps. This setup would produce 156 watts of power. In series, the voltages add up to 24 volts, but the current is limited to the smaller panel's output of 5 amps, resulting in 120 watts of power. Essentially, parallel gives you more power because both panels contribute fully, while in series, the weaker panel holds the system back.

Now that we understand this, I would get rid of them and go with new every single time. It often makes more sense to replace old or mismatched panels with new ones to maximize performance and avoid inefficiencies.

The Scenario

With solar panel prices at record lows, issues like these mostly arise with older systems. However, the real challenge now comes when a system is only 5 years old and the owner wants to upgrade. Five years ago, 250-300 watt panels were the standard, but today, panels with capacities of 500-600 watts or more are common, and next year’s models are expected to be even more powerful. As solar technology advances at such a rapid pace, inverters and controllers are struggling to keep up. We are now seeing hybrid inverters with large, high-voltage MPPTs built in, along with microinverters for grid-tied systems, all expanding voltage capabilities to match the increasing size and power of solar panels.

Why Mixing Solar Panels Happens and What to Consider

Expanding or upgrading a solar panel system often involves mixing different panels. This can happen for several reasons:

• System Expansion: Adding panels to meet growing energy needs.
• Panel Replacement: Swapping out damaged or outdated panels.
• Availability Issues: Original panels are no longer produced or available.
• Cost Considerations: Using more budget-friendly options for expansion.

While these reasons are common, mixing panels isn’t always straightforward and requires careful planning to avoid performance issues.

Key Considerations When Mixing Panels

1. Electrical Compatibility: Panels should have similar voltage and current ratings to prevent energy loss.
2. Wiring Configuration: Parallel connections work better for mismatched wattages, while series setups rely on matching current output.
3. System Components: Ensure your inverter, charge controller, and wiring can handle additional panels without causing inefficiencies.
4. Regulations: Adding panels may require permits or updated interconnection agreements.

Common Challenges

• Reduced System Efficiency: Mismatched panels often lead to energy losses, as the system typically operates at the level of the lowest-performing panel.
• Inverter and Controller Compatibility: Modern panels may not be compatible with older inverters or charge controllers, necessitating additional upgrades.
• Potential Overheating: Differences in electrical characteristics can cause overheating, which may damage components over time.

Best Practices for Mixing Panels

• Use MPPT Controllers: These optimize power output from mismatched panels.
• Group Similar Panels: Keep panels with matching specs in the same circuit.
• Separate Arrays: For significantly different panels, set up a separate inverter or charge controller.
• Consult Professionals: Expert advice ensures your system remains efficient and safe.

In short, mixing solar panels can work, but it requires thoughtful design and sometimes additional equipment. For the best results, consult a professional to ensure your system runs efficiently and reliably.

Strategies for Successfully Mixing Panels

When I assess an older off-grid roof with a solar array, let's say 3 or 6 panels, that's 5 years old and still functioning well with its existing controller, the system is likely operating at 24 volts, with either a 24-volt or 48-volt inverter and battery bank. In this case, I’d leave the existing array as is and add a new array with similar wattage, along with a new controller to integrate with the system. We can't simply expand the old controller, and if it had room for expansion, that should have been done within the first couple of years. Although it might be possible to match the new array with the old system, the simplest approach is to add a new controller, new panels, and connect them to the matching battery bank.

If the system were 12 volts, however, I would already recommend upgrading to a 24-volt or 48-volt system. A 12-volt system has very limited options for expansion, and it's not practical to continue with that setup.

If we're talking about an RV with a 12-volt system, and there’s still room on the roof or the option to connect a second portable array with an extended cable to find more sunlight when parked under trees, this presents a different scenario. In this case, if the system is 12 volts, you would need a new controller to accommodate the additional panels. However not going the portable panel route, there is limited space on an RV roof, so expansion options are constrained.

Today, some RV owners are upgrading to 48-volt systems due to their increased efficiency, which allows for better performance with less space needed for wiring and components.

Conclusion

While expanding or upgrading your solar system by mixing different panels can be a practical solution, it is essential to carefully evaluate the potential challenges it may bring. Variations in wattage, voltage, technology, and age can all impact the overall performance of your system. However, with the right strategies, such as using MPPT charge controllers, installing microinverters in the grid-tie world, and consulting with a professional, you can mitigate these issues and optimize your system’s efficiency.

By taking the time to plan your system expansion thoughtfully, you can ensure that your solar investment continues to provide reliable, sustainable energy for years to come. At IOTG Solar, we are committed to helping you make the most of your solar system and guide you through every step of the process.

At IOTG Solar, we specialize in designing and upgrading solar systems tailored to your unique needs. If you’re considering expanding your solar installation, reach out to us for expert advice and solutions that maximize your energy production.

IOTG Solar: Helping you design smarter solar systems through education.

For individuals seeking consultation, education, or assistance in system designs related to off-grid solar applications, IOTG Solar stands ready to help. Our team is available to address questions, provide valuable insights, and offer support at every stage of the solar energy journey. Feel free to reach out to ?IOTG Solar? anytime for expert assistance and comprehensive solutions tailored to your specific needs.

IOTG Solar...

Keeping you powered through education.