Why Are Only Half My Solar Lights Working


The most likely reason only half of your solar lights are working is that the lights are wired in two parallel strings, so when one string fails, the others continue working.

This article will explore the internal wiring that allows solar lights to operate this way. We will also provide troubleshooting tips to identify and fix the main issues causing half of your solar lights not to work.

Let’s look at the basics of how solar lights work. By understanding solar lights’ fundamentals and wiring, you can diagnose the root causes of partial outages and get all your lights working again.

How Do Solar String Lights Work?

The key component in solar-powered lights is the solar panel. Inside the panel are solar cells that convert direct sunlight into electricity during daytime hours.

This generated power charges a built-in lithium battery that stores the electricity. The battery acts as a solar power reservoir, holding the power until needed at night.

After sundown, when it’s dark, the stored solar electricity flows from the battery to illuminate the strand of bulbs.

Next, let’s talk about wiring.

What Are the Possible Wiring Configurations?

There are a few different options when it comes to wiring configurations:

Series Wiring

String lights in series wiring arrangement

In series wiring, the bulbs are connected end-to-end in a continuous loop. Electricity flows from the battery through each bulb in sequence before returning to the battery.

Like old-fashioned Christmas lights, if one bulb goes out, it creates an open circuit, and the whole string turns off.

Parallel Wiring

String lights in parallel wiring arrangement

In parallel wiring, each light bulb has its own individual wire connecting it directly to the battery. They are on separate parallel circuits rather than one continuous loop.

If one bulb burns out, the others stay illuminated. However, parallel wiring requires more extensive wiring and is more expensive.

Series-Parallel Combination

String lights in series- parallel wiring arrangement

This hybrid approach combines aspects of series and parallel wiring. Shorter series strings of bulbs are wired together in parallel.

For example, two series strings of 15 bulbs may be wired in parallel. If a bulb goes out in one series, the other continues working.

What is the Most Common Wiring Arrangement?

The most common wiring arrangement is two solar light strings connected in parallel

The most common configuration for solar string lights is two parallel strings of lights. Each string consists of a string of bulbs connected in series.

This dual parallel wiring requires less wiring than a fully parallel design. Two wires run the length of the light strand, connecting to each series loop at intervals. The parallel circuits then connect back to the solar panel and battery.

What Are the Reasons Behind Only Half the Lights Working?

Having two separate series strings connected in parallel is why only half of your solar lights stop working while the other half continues to run.

Since each series circuit is independent, the others connected in parallel can keep glowing if one series fails.

Several common factors can lead to this partial failure. As we examine below, identifying the specific problem is key to getting all your lights glowing again.

Loose, Corroded, or Damaged Bulb

One possible reason half of your solar string light not working is a problem with an individual bulb’s connection. Over time, bulbs can loosen in their sockets. This breaks the vital electrical contact needed to complete the circuit.

Corrosion is another enemy, especially in seaside climates. This adds resistance that impedes the flow of current.

Sometimes the culprit is physical damage to a bulb or its socket. This degrades the connection and again opens the circuit.

Blown Fuse

Many solar string lights contain a small glass fuse inside the battery housing. This fuse is designed to blow and open the circuit if there is a significant electrical overload.

Problem with Shunt in the Bulb

Incandescent bulbs are prone to malfunction. A tiny wire called a shunt is in a light string inside each bulb. If the bulb dies, the shunt acts as a detour to bypass the dead bulb and complete the circuit.

But sometimes, these microscopic shunts break down as well. When this happens in a single LED bulb, it creates an impassable roadblock in the electrical loop. And just like a fallen tree across a highway, that obstruction shuts off power to all the bulbs that follow.

Damaged Wiring

The thin wiring inside solar lights is exposed to the weather and animals like squirrels. Any compromise in the wiring insulation can lead to an open circuit and a half-dead string of lights.

Wires can also crack and fray from repeated bending.

Moisture Causing Damage

Outdoor moisture is unavoidable, but its infiltration can be minimized with good weatherproofing. When water seeps into light strands, it can cause corrosion and oxidization over time.

This buildup degrades the conductive properties of the wires and connectors. The accumulated resistance eventually causes an open circuit failure in parts of the loop.

How to Fix Partially Turned Off Lights

Partially turned off string lights at dawn

Finding that only some of your solar string lights turn on while others remain dark can be frustrating. But don’t worry – with some troubleshooting, you can easily fix solar lights.

Here are the steps you should take to fix solar lights that are partially off:

Check Connections

Inspect all the wiring connections between solar panels, batteries, junctions, and individual bulbs. Look for any corroded, loose, or damaged wires and connectors.

These faulty connections create openings in the closed circuit, preventing electricity from flowing properly.

  • Use a wire brush to clean any corroded connections gently.
  • Tighten any loose wiring connections.
  • Replace cracked wire coverings with electrical tape.
  • If any wires are broken, splice in a new section of wiring.
  • If connection points are severely damaged, you may need to replace the solar panel, battery housing, or other components.

Replace Blown Fuses

To replace blown fuses, follow these steps:

  • Check each fuse and look for any that are blackened or appear blown.
  • Carefully pull these out and replace them with the same amp-rating fuses.

Check Shunts in Incandescent Bulbs

A single bulb going out should not result in half of your solar lights not working due to the presence of the shunt. But if the shunt is also blown, do the following:

  • Test the blown-out bulbs with a multimeter or bulb tester to identify faulty ones.
  • Remove any dead bulbs and check that the shunt wires are intact.
  • If the shunt is broken, replace the entire bulb.

Fix Broken Wires

Inspect the entire length of the wires for any cracks, frays, or breaks in the plastic insulation. Also, look for sections with exposed copper wire. Damage often happens at connection points or where wires are exposed to the elements.

  • Use electrical tape to seal small cracks or frays in the wire covering.
  • For broken wires, splice in a new wiring section using wire nuts.
  • Replace any sections with severe wire damage.

What Causes a Full Set of Solar Lights to Not Turn On?

If your entire string of solar lights fails to turn on at night, there are several possible reasons:

  • The on/off switch is turned off.
  • You forgot to remove the pull tab on the battery from a new solar light.
  • Your outdoor solar lights are dirty or covered in debris.
  • A solar light wire is damaged.
  • Rechargeable batteries are old and can no longer hold a charge.
  • The solar panel is not getting enough sunlight per day.
  • Rain, snow, or moisture has caused internal water damage.
  • Nearby light sources like streetlights are confusing the solar light sensor.
  • The solar light sensor or motion sensor is faulty.
  • The timer function has automatically turned off the lights
  • Internal electrical components or circuitry have failed.

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