Why Does My LED Strip Get Dimmer at the Far End?
If you have ever installed an LED strip longer than 5 meters and noticed the lights gradually dimming toward the end, you have experienced voltage drop. This is the single most common installation issue reported by contractors and DIY installers alike — and it is entirely preventable with proper planning.
In this guide, BrightLink LED explains the science behind voltage drop, shows you how to calculate it before your installation, and provides proven solutions to ensure uniform brightness across your entire LED strip run.
Understanding Voltage Drop: The Science
LED strips operate on low-voltage DC power — typically 12V or 24V. As electrical current travels through the copper traces on the strip’s PCB, it encounters resistance. This resistance causes the voltage to decrease progressively along the length of the strip.
The key principle: the longer the run and the higher the current draw, the greater the voltage drop. A 12V strip might receive 12V at the connection point but only 10.5V at the far end of a 10-meter run — resulting in visibly dimmer LEDs.
Why 24V Systems Are Preferred for Commercial Projects
This is exactly why professional installations favor 24V LED strips over 12V for runs longer than 5 meters. At double the voltage, the current is halved for the same power, which reduces voltage drop by approximately 75%. With 24V strips, you can achieve uniform brightness up to 10 meters from a single feed point.
How to Calculate Voltage Drop
The formula is straightforward:
Step 1: Determine Total Current Draw
Multiply the strip’s power per meter (W/m) by the total length, then divide by the system voltage:
Current (A) = Power per meter (W/m) × Length (m) ÷ Voltage (V)
Example: A 14.4 W/m, 12V strip at 8 meters draws: 14.4 × 8 ÷ 12 = 9.6A
Step 2: Estimate Voltage Drop
Most manufacturers provide voltage drop data per meter. As a general rule for standard 2-layer PCB strips with 8mm width:
- 12V systems: Maximum recommended run = 5 meters from single feed
- 24V systems: Maximum recommended run = 10 meters from single feed
- Constant current (CC) strips: Up to 20 meters with minimal drop (see below)
As a guideline, voltage drop should not exceed 5% of nominal voltage (0.6V for 12V, 1.2V for 24V) to maintain consistent brightness and color temperature.
Five Proven Solutions to Prevent Voltage Drop
1. Use 24V Instead of 12V
As discussed, switching to 24V strips immediately doubles your maximum run length. For any commercial project with runs exceeding 5 meters, 24V should be your default specification.
2. Feed Power from Both Ends
For runs between 10–20 meters, connect the power supply to both ends of the strip. This effectively halves the electrical length, as current travels from each end toward the center. This is the simplest and most cost-effective solution for medium-length installations.
3. Add Intermediate Feed Points
For very long runs (20+ meters), run a parallel set of main cables alongside the strip and tap power into the strip every 5–10 meters. This approach is commonly used in commercial cove lighting and linear installations.
4. Use a Larger Wire Gauge for Extension Cables
If your power supply is located far from the strip, the extension cables themselves can contribute to voltage drop. Use 14 AWG or thicker wire for runs over 3 meters from the driver to the strip. For runs over 10 meters, consider 12 AWG.
5. Specify Constant Current (CC) LED Strips
Constant current LED strips use onboard IC chips that regulate current regardless of voltage fluctuations along the strip. These strips maintain identical brightness from start to finish — even on 20-meter runs from a single feed point. They are more expensive per meter but eliminate voltage drop entirely and reduce installation labor costs.
Diagnosing Existing Voltage Drop Problems
If you are troubleshooting an existing installation with dim sections, check these items in order:
- Measure voltage at the strip input: Use a multimeter to confirm the power supply is delivering the correct voltage under load. A 12V supply reading 11.2V under load may be undersized.
- Check wire gauge and connections: Thin wires and loose terminal connections add resistance. Tighten all connections and replace undersized wires.
- Verify power supply capacity: The driver should be rated for at least 120% of the total strip wattage. Running a driver at 100% load causes voltage sag.
- Look for corrosion or oxidation: In outdoor or high-humidity installations, corroded solder joints and connectors can create significant resistance points.
Best Practices for Contractors
Professional installers should adopt these habits to eliminate voltage drop callbacks:
- Always calculate voltage drop before quoting a project
- Default to 24V strips for any run over 5 meters
- Include a wiring diagram showing feed points in your installation proposal
- Use a voltage drop calculator app during site surveys
- Keep constant current strips in inventory for long-run applications
At BrightLink LED, we provide complete technical support for your LED strip installations — from voltage drop calculations and wiring diagrams to on-site commissioning guidance. Our 12V and 24V strips are manufactured with heavy-duty 2oz copper PCBs to minimize resistance, and our constant current series delivers uniform brightness on runs up to 20 meters.
Need Help Planning Your LED Strip Installation?
Contact BrightLink LED for free installation consultation and wiring diagrams. Our technical team supports contractors and project specifiers worldwide.
Email: sales@brightlinkled.com | WhatsApp: +86-135-1234-5678