Solar Street Light Flickering: Causes & Solutions

Solar street lights are widely used in urban roads, parks, residential areas and remote regions due to their advantages such as environmental friendliness, energy conservation and no need for wiring. However, in actual use, the "flickering" problem frequently troubles users and operation and maintenance personnel. This not only affects the visual comfort of night lighting and pedestrian safety, but also may indicate potential electrical faults - such as loose wiring, driver damage or battery aging. If neglected for a long time, it may also accelerate the aging of circuit components and even cause fire hazards.
 

Next, NOKIN will systematically analyze the causes of solar street light flickering, the methods for judgment, and the corresponding solutions. It will also provide a set of actionable troubleshooting lists and preventive suggestions to help you quickly locate and thoroughly solve the problem.

How to accurately determine if a solar street light is "Flickering"?

Flickering ≠ Normal Switch

In technical terms, "flickering" refers to the periodic or irregular fluctuations in the brightness of light within a short period of time. It is different from normal switch actions and can be divided into two categories:

Continuous flashing: The light alternates between bright and dark at a fixed frequency.

Intermittent flickering: Suddenly dimming or going out and then brightening up irregularly.

Naked Eye vs. Tools: How to Identify Solar Street Light Flickering?

The naked eye is more sensitive to low-frequency flicker (<80Hz), but high-frequency flicker (>100Hz), although invisible, may interfere with the operation of cameras, mobile phone shooting or electronic devices.

Practical judgment method

Mobile phone video recording method:

Record the video at 60fps or a higher frame rate, and observe whether there are stripes or light and dark transitions when playing it back.

Multimeter measurement:

Monitor whether the voltage at the power supply terminal of the light is stable (normally, the fluctuation should be less than ±5%).

Oscilloscope detection (professional scenario) :

Directly observe the output waveform of the LED driver to determine if there is excessive ripple or unstable current.

6 Reasons for the Solar Street Light Flickering

LED Driver/Power Supply Failure

Driver failure not only causes flickering but may also burn out the LED beads.

The driver is responsible for converting the direct current from the battery into a constant current output for the LED to use. If its voltage stabilizing or constant current function is abnormal, it will cause current fluctuations, thereby triggering flickering. This is the most common and frequently-occurring fault point.

Insufficient Battery Voltage or A Decline in Health

The battery is the energy core of the system, and its condition directly affects the stability of the entire light. When the battery ages (capacity attenuation >30%) or is undercharged, the discharge voltage drops rapidly at night, triggering the low-voltage protection mechanism of the controller and causing the lights to flicker.

Loose Wiring, Corrosion or Poor Contact

Poor contact is a "hidden killer". It is not easily detectable in the early stage but has serious consequences. Changes in temperature and humidity in the outdoor environment, salt spray corrosion or improper installation can lead to an increase in the resistance of the terminal blocks. When the load changes, a voltage drop occurs at the contact points, which is manifested as intermittent flickering.

Abnormal Behavior of Charge and Discharge Controller (PWM vs MPPT)

The controller algorithm directly affects the quality of the system's dynamic response. Some low-cost PWM controllers adjust power in a pulsed manner under low light or light load conditions, resulting in visible flickering to the human eye. The MPPT controller usually has a smoother output.

Internal Faults of the Light Beads or Light Board

Poor soldering at the internal solder joints of the LED module, damage to the driver IC or short circuit of individual LED beads can lead to an imbalance in current distribution, causing local areas to flicker or not light up at all. It should be noted that for module-level faults, the entire board needs to be replaced, which incurs relatively high costs.

The Failure of Waterproofing/Sealing Led to Moisture and Short Circuit

A damp environment can accelerate metal corrosion and insulation failure. When the sealing ring of the controller or junction box ages or the casing cracks, moisture can invade and cause short-term circuit failure, which is manifested as intensified flickering after rain or in the early morning.

6 Solutions for the Solar LED Street Light Flickering

Replace or repair the LED driver

Test method

Disconnect the light and measure the output current/voltage waveform of the driver with an oscilloscope. If the ripple is greater than 10%, it is considered abnormal.

Solution

Replace it with a driver featuring constant current output, low ripple (<5%), and high power factor (PF>0.9).

Give priority to industrial-grade models with four protections: overvoltage, overcurrent, short circuit and overheating.

Cost reference

High-quality drives are priced at approximately $15 to $35 each.

Check and restore the battery health

Measurement steps

During the day: Measure the charging voltage of the solar panels (for lead-acid batteries, it should reach 13.8-14.4V, and for LiFePO4, it should be 14.2-14.6V).

At night: Measure the terminal voltage of the battery under load. If it is 10% lower than the nominal value (for example, in a 12V system, it is less than 10.8V), it indicates that the battery is aging.

Solution

Aged batteries (used for more than 2 years and with a significant decrease in capacity) should be replaced.

Make sure the controller Settings match the battery type (for example, a dedicated charging curve is required for LiFePO4).

Battery cost reference

A 12V 20Ah LiFePO4 battery costs approximately $80 to $120, while a lead-acid battery costs around $30 to $50.

Fixed and anti-corrosion treated wiring

Key inspection points

The junction box inside the light pole, battery terminals, solar panel connectors, and grounding wires.

Solution

Re-crimping the terminals, using waterproof terminal caps or IP68-level waterproof connectors.

Apply conductive anti-oxidation paste and wrap it with heat shrink tubing to enhance sealing.

Cost reference

The cost is extremely low (< $2 per point), but the effect is remarkable.

Adjust or upgrade the controller (PWM → MPPT)

Test method

At night when the load is low, use an oscilloscope to observe whether the controller output shows sawtooth-shaped pulses.

Solution

Upgrade the low-end PWM controller to a high-quality MPPT controller, which features a faster dynamic response and more stable output.

Or choose an advanced PWM model with "soft start" and "constant current maintenance" functions.

Cost reference

The price of an MPPT controller is approximately $40 to $80, which is more expensive than a regular PWM ($15 to $25), but it offers higher long-term reliability.

Inspect or replace the light board /LED module

Inspection method

Visually check for black spots, bulges, or cracked solder joints.

After powering on, observe whether there is a single LED not lighting up or flashing partially.

Solution

Replace the faulty light board as a whole to avoid uneven light efficiency caused by local maintenance.

When purchasing, choose products with good heat dissipation of aluminum substrates, IP65 or above protection, and a warranty of more than 2 years provided by the manufacturer.

Cost of the light board

A 30W street light panel is approximately $20 to $40.

Check for waterproofing and sealing issues

Key points for inspection

Are there any cracks in the controller housing?

Is the sealing ring of the junction box hardened or deformed?

Are there any water stains, mold spots or condensation inside?

Solution

Replace the aged sealing ring (silicone material is more weather-resistant).

Drill micro-drainage holes (with a diameter of 1-2mm) at the bottom of the junction box to prevent water accumulation.

Use potting compound to perform secondary sealing on the key circuits.

Solar Street light Flickering Check Practical Operation List

Step 1: Visual Inspection and Environmental Examination

Check if the solar panels are blocked by leaves or dust (observe if they recover after cleaning).

Check whether the light body and junction box are damaged, rusted or have any water ingress marks.

Step 2: Measure the Battery and Panel Data

Measure the open-circuit voltage (Voc) and operating voltage (Vmp) of the solar panels during the day.

Measure the no-load voltage of the battery and the load voltage when it is lit at night.

If Vmp is less than 80% of the nominal value, it indicates insufficient power generation. If the load voltage drops sharply at night, it indicates a battery problem.

Step 3: Test the Drive Output

Disconnect the LED load and connect a dummy load (such as a resistor) to measure the driver output.

Capture the waveform with an oscilloscope or a high sampling rate recorder to determine if it is stable.

Step 4: Check All the Terminal Blocks

Manually tighten all the screw terminals and observe whether the flashing disappears immediately.

If it disappears, it is confirmed to be poor contact and permanent anti-corrosion sealing treatment is required.

Step 5: Diagnosis by Substitution Method

Temporarily replace the test with a known good drive or battery.

If the problem disappears, the faulty module can be identified to avoid blind replacement.

Suggestion: Record the voltage/current data after each operation, establish a maintenance file, and facilitate subsequent analysis and claims from the manufacturer.

Eliminate the Flickering of Solar Street Lights from the Design Source

Key Points for Selection

Driver: Select a model with low ripple (<5%), high PF (>0.9), and multiple protections.

Battery: LiFePO4 batteries are preferred (with a cycle life of over 2000 times and a wide operating temperature range of -20 ° C to 60 ° C). Although the initial cost is high (about $100), the TCO over 5 years is lower.

Controller: Avoid ultra-low-priced PWM products and choose models with temperature compensation and intelligent charge and discharge management.

Design Optimization

All exposed wiring uses tin-plated copper wire with waterproof connectors.

The interior of the junction box is sealed with secondary potting, and the outer shell is reserved with a micro-ventilation/drainage structure.

The light body structure avoids dead corners with water accumulation, and the inclination Angle is ≥5° to facilitate drainage.

Solar Street Lights Maintenance Plan

Quarterly inspection: Clean the photovoltaic panels, check the wiring tightness, and test the waterproof performance.

Annual test: Evaluate the battery health (SOH) using a battery internal resistance meter or discharge tester.

Establish an electronic maintenance log to track the historical faults of each light.

Analysis of Solar Street Light Flickering Real Cases

Case A: 50 Solar Street Lights in the Community Flicker Intermittently at Night

Phenomenon: After nightfall, a few solar street lights flicker randomly without any pattern.

Investigation: Technicians opened the junction box of the light post and found that a large number of terminals were loose and severely oxidized.

Solution: Re-crimping + replacing the IP68 waterproof connector + applying anti-oxidant.

Result: The problem was solved 100%, and there was no flickering of solar street lights in the following year.

Case B: The surveillance footage on a remote section of the road flickers

Phenomenon: It is almost invisible to the naked eye, but strong stripes appear in the surveillance video at night.

Reason: The use of a cheap PWM controller causes high-frequency pulses to interfere with the camera's CMOS sensor.

Solution: Replace with an MPPT controller (with EMI filtering).

Effect: Flickering disappears, and the system's power generation efficiency increases by 12% (measured data from YouTube).

FAQ

What is the most common cause of solar street lights flickering?

It mainly includes: insufficient battery voltage/capacity attenuation, abnormal driver, loose wiring, low-load adaptation issues of the PWM controller, and failure of the waterproof seal.

I can't see the flicker when recording videos on my mobile phone. What should I do?

Record with a high frame rate camera of ≥60fps (slow playback observation), or detect with an oscilloscope/high sampling rate voltage recorder; Simple method: Use a multimeter to measure the static voltage of the battery and the load voltage. If the difference exceeds 0.5V, it is very likely that there is a problem with the battery or the wiring.

Can replacing the battery solve the flickering problem?

It is only effective when the flickering of solar street lights is due to insufficient battery voltage or capacity attenuation. If the problem lies with the driver, wiring or controller, replacing the battery will be ineffective.

Can a PWM controller cause solar street lights to flicker?

Yes, it is more likely to occur under low-load conditions. In the short term, the power reduction threshold can be adjusted. In the long term, it is recommended to upgrade to an MPPT controller or match it with a higher-power LED light source.

Can the "tightening terminal" be used on site as a temporary repair?

Temporary repair: Sure! The flickering caused by loose wiring can be quickly restored by tightening the terminals on site with tools, cleaning the oxide layer on the joints (sanding and rewiring), but anti-corrosion treatment should be carried out and permanent repair should be done under safe conditions.

 

The problem of solar street lights flickering sometimes does not draw much attention from people. However, when it occurs and is not dealt with in time, it will affect the service life of the solar street light system and the user experience. The above content is a summary of the causes of solar street light flickering and the methods for troubleshooting and solving problems, compiled by NOKIN based on years of industry experience and user feedback. Through scientific troubleshooting, reasonable selection and regular maintenance, the flickering problems of the vast majority of solar street lights can be prevented or quickly resolved. Remember: Early detection and early handling can ensure that green lighting truly "shines" with peace of mind.