Last updated on Aug 17, 2024

What are the pros and cons of using a bypass diode instead of a blocking diode?

If you have a solar system, you might have heard of diodes. Diodes are electronic devices that allow current to flow in one direction only. They are often used in solar systems to protect the batteries from reverse current and to improve the performance of the solar panels. But not all diodes are the same. In this article, we will explain the difference between a bypass diode and a blocking diode, and the pros and cons of using one instead of the other.

1 What is a bypass diode?

A bypass diode is a diode that is connected in parallel with a solar panel or a string of solar panels. Its purpose is to bypass the current around a panel or a string that is partially shaded or damaged. This prevents the shaded or damaged panel or string from reducing the output voltage and power of the whole system. Bypass diodes also reduce the risk of hot spots, which are areas of high temperature and resistance that can damage the solar cells.

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Ayush Bajpai

Senior Consultant ESG/Sustainability/Carbon Accounting/GHG /18K+ Followers/Content Writer Master of Business Administration - MBA Energy Management from School of Energy and Environmental studies DAVV, Indore
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Using a bypass diode instead of a blocking diode offers the benefit of allowing current to bypass shaded or malfunctioning solar cells, minimizing power loss in the entire panel. This enhances system efficiency, especially in partial shading conditions. However, bypass diodes do not prevent reverse current flow like blocking diodes, making them unsuitable for protecting the battery at night. The primary drawback of a bypass diode is its inability to stop reverse leakage, meaning a blocking diode is still needed for battery protection, which adds complexity to the system.

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2 What is a blocking diode?

A blocking diode is a diode that is connected in series with a solar panel or a string of solar panels. Its purpose is to block the reverse current from the battery to the panel or the string at night or when the panel or the string is not producing enough power. This prevents the battery from discharging through the panel or the string and losing its charge. Blocking diodes also protect the panel or the string from overvoltage and overcurrent that can occur due to faults or surges in the system.

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Corey Clemons

Renewable Energy Operations | Beekeeper | UAS Pilot
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In the case of miss wiring during installation a fire is prevented by a wiring in an in line blocking diode. A blocking diode will also help in fire prevention of damaged panels and panel reuse.

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3 Pros of using a bypass diode

Using a bypass diode has several advantages for your solar system. First, it improves the efficiency and reliability of your system by allowing the current to flow around the shaded or damaged panel or string, instead of through it. This means that you can get more power from your system even when some panels or strings are not working optimally. Second, it reduces the stress and degradation of your solar cells by preventing hot spots and overheating. This means that you can extend the lifespan and performance of your panels or strings.

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4 Cons of using a bypass diode

Using a bypass diode also has some drawbacks for your solar system. First, it adds some complexity and cost to your system by requiring more wiring and components. You need to install one bypass diode for each panel or string, and you need to ensure that they are compatible with the voltage and current ratings of your system. Second, it introduces some power loss and voltage drop in your system by diverting the current around the panel or string. This means that you might need more panels or strings to achieve the same output power and voltage as without bypass diodes.

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5 Pros of using a blocking diode

Using a blocking diode has some benefits for your solar system as well. First, it protects your battery from reverse current and discharge by isolating it from the panel or the string at night or when the panel or the string is not generating enough power. This means that you can preserve your battery's charge and capacity and avoid wasting energy. Second, it protects your panel or the string from overvoltage and overcurrent by limiting the flow of current from the battery to the panel or the string. This means that you can prevent damage and fire hazards to your panels or strings.

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6 Cons of using a blocking diode

Using a blocking diode also has some disadvantages for your solar system. First, it reduces the output power and voltage of your system by consuming some of the current and voltage from the panel or the string. This means that you might need more panels or strings to achieve the same output power and voltage as without blocking diodes. Second, it creates some heat and resistance in your system by dissipating some of the power and voltage from the panel or the string. This means that you might need to provide some cooling and ventilation for your diodes and your system.

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Clive T.

Change Agent | CXX | IoT | Strategic Project Leader | Coach-Mentor | 20+ Years in Blue Chip organisations
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Note that this is a tiny disadvantage as the diode needs a mere 0.6v to overcome the forward direction of current, and once 'on' it consumes almost no current at all. It should not get hot if specified correctly, always use the short-circuit current of the string plus 20%. ( panel ISC x number of panels in the string, +20%).

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7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?

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What are the pros and cons of using a bypass diode instead of a blocking diode?

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1 What is a bypass diode?

2 What is a blocking diode?

3 Pros of using a bypass diode

4 Cons of using a bypass diode

5 Pros of using a blocking diode

6 Cons of using a blocking diode

7 Here’s what else to consider

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