Why Is My Solar Street Light Not Working? A Troubleshooting Guide

A solar street light has four parts that can fail: the panel that charges, the battery that stores, the controller that decides, and the LED that lights. When a light goes dark, the LED is the least likely culprit. This guide sorts the symptoms into causes, so a maintenance crew can find the problem in one visit instead of swapping parts until it works.

Start with the symptom

The most common cause: charging

Most lights that “stop working” are simply not charging enough. A light that was sized with a sensible margin can lose it to dirt, shade or a failing connector.

We ran an example in our battery autonomy calculator: a 30 W light with a 60 Ah, 12.8 V LiFePO4 battery and a 100 Wp panel at 4.5 sun hours.

• Clean panel: about 324 Wh collected on a sunny day against 237 Wh used at night. The light covers about 3.7 rainy days and refills in about 6 sunny days.
• Panel output halved by dust or shade (effectively 60 Wp): only about 194 Wh collected. The panel can no longer cover a single night, even on a sunny day. The battery drains a little every day until the light switches off early.

Open this example and set the panel back to 100 Wp to see the difference.

Check the panel

• Dust, bird droppings, leaves: clean with water and a soft brush. In dusty regions, clean every few months.
• New shade: trees grow and buildings go up. Check shade at midday and in the season when the sun is lowest.
• Orientation: a panel knocked out of alignment, or installed facing away from the equator.
• Damage: cracked glass, burned cells or a damaged junction box.
• Connections: in split systems, check the panel cable and connectors for corrosion and looseness.

Second most common: the battery

Batteries wear out. A LiFePO4 battery typically lasts 5–8 years in street lighting, a gel battery 2–4 years. As capacity falls, autonomy falls with it: in the example above, a battery that has lost 30% of its capacity covers only about 2.6 rainy days instead of 3.7. The light still works in good weather, so the problem appears first in the rainy season.

Signs of a worn battery and how to plan replacement are covered in how long do solar street lights last.

Controller and settings

• Wrong schedule: check the light is not set to full power all night when it was sized for dimming.
• Wrong battery type setting: a controller set for lead-acid on a lithium battery (or the reverse) charges incorrectly.
• Low-battery protection: the light may be correctly switching off to protect a battery that is not charging. Fix the charging, not the controller.
• Reset after faults: some controllers need a reset after the battery has been fully discharged.

Wiring, water and the LED

• Water ingress into the housing or battery box: look for condensation, corrosion and failed seals.
• Loose terminals after transport, vibration or theft attempts.
• LED or driver failure is rare compared with the issues above, but a light with good battery voltage, correct settings and no output points to the driver or LED board.

When the system was too small from the start

If a light fails every rainy season from the first year, the system was probably undersized for the site. No maintenance will fix that; the panel, the battery or the schedule must change. Check the original design against the site’s worst-month sun hours with the solar street light calculator, and see how many rainy days a solar street light can last.

A 15-minute field check with a multimeter

A technician with a multimeter, a ladder or platform and the controller’s remote or app can find most faults in one visit. A practical order:

1. Look first. Panel dirty or shaded? Housing cracked or full of water? Cables chewed, cut or loose?
2. Panel voltage in daylight. Disconnect the panel from the controller and measure across its leads. A typical “12 V” panel (36 cells) should show roughly 19–23 V open-circuit in good light. Near zero means a broken cable, connector or junction box; a low reading in full sun points to damaged cells.
3. Battery voltage. Measure at the battery terminals with the load off. See the table below.
4. Charging current. With a clamp meter or the controller display, check that current flows into the battery in sunlight. Good panel voltage but no charging current means a controller or wiring fault.
5. Controller settings. Battery type, schedule, dimming levels, low-voltage cut-off and the dusk threshold.
6. Load test. Cover the panel (or use the test mode) and check that the light switches on and the LED draws the expected current.

Reading a 12.8 V LiFePO4 battery

LiFePO4 holds an almost flat voltage over most of its charge, so voltage is only a rough guide, best measured after the battery has rested for an hour:

A battery that reads full in the afternoon but cannot run the light for a whole night has lost capacity: the voltage looks fine because voltage measures charge level, not how much energy the battery can still hold. For gel batteries the voltages are lower (about 12.7 V full, 12.0 V nearly empty) and the curve is steeper.

Repair or replace?

On large projects, replacing all batteries on a street at once is usually cheaper than chasing individual failures.

Keep a record

For every light visited, note the pole number, symptom, battery voltage, panel condition and what was fixed. Patterns across a project (all lights on one street, all lights from one batch) point to causes that a single visit cannot. If you have our solar street lights on site, send us the pole numbers and symptoms and our engineers will help diagnose them.