Why Are My LED Lights Dim? Stopping Excessive Voltage Drop

Have you ever asked yourself, why are my LED lights dim after completing a project? The answer is likely voltage drop.

While the voltage of every LED strip light decreases from the power source to the end of the strip, most individual five meter LED strips are designed so that dimming from typical voltage reduction is not noticeable.

When connecting multiple strips, the voltage drop can cause LEDs at the end of the strip to appear dimmer than those at the beginning. The longer the LED strip, the more significant the voltage drop will be.

Ultimately, the LEDs at the strip's end may not illuminate. Preventing excessive voltage drop requires using the appropriate wire gauge and power supply for the length of your LED strip.

The main contributing factors to excessive voltage drop in LED strip lights are project length, maximum run, and voltage. This article will cover several approaches to reduce the impact of voltage reduction across LED strip lights and solutions for long LED strip light runs. 

Completing your installation without excessive voltage drop across LED strip lights is easy if you follow these guidelines.

Start by selecting a power supply that will offer enough power to your strip lights. Use our convenient LED Strip Light Power Supply Calculator to determine the output your project requires and round up to the nearest wattage.

Manufacturers design LED strip lights to use only the required power from the power supply. Additional padding of extra wattage from a larger power supply allows more efficient operation reducing heat and extending the life of your components.

Also, consider that you may need a power supply that meets NEC Class 2 standards for safety and code compliance. Class 2 standards help reduce the risk of shock and fire hazards and may be required in some areas. See our post on the Difference Between Class 2 and Class II Power Supplies for more information.

If installing a strip in a vehicle, you will connect it directly to the vehicle’s electrical system and do not need an additional power supply so long as the vehicle's operating voltage matches the strp's voltage.

See our article LED Strip Lighting: Choosing the Right LED Power Supply for more information.

For LED strip lights that do not exceed the maximum run, simply install the power supply, strip, and any accessories, and you are ready to go. If your project calls for going beyond the max run of your strips, you have a few options. If you can place your power supply near the center, you can effectively double the length of your run if the strips do not need to be connected.

Once you have decided on the correct power supply and defined the max run of your strips, you can plan the circuit wiring.

There are two wiring options for a project that exceeds the max run length of your LED strip lights.

For directly connected strips, power the run from both ends to extend the run length to double the max run of the individual strip lights.

Choose option two for multiple strips covering a long distance. Wire the strips back to the power supply at intervals, allowing you to extend the run indefinitely within the limits of the power supply specifications.

We offer 22 AWG wire for simple installations and 18 AWG wire for more demanding installs. The larger the gauge, the lower the resistance per meter and the lower the voltage reduction. Contact your electrician for assistance or one of our customer support specialists for more information.

Use an amplifier to avoid excessive voltage drop across LED strips with multiple colors. An amplifier is needed because each wire on a multi-color strip needs its voltage boosted. Amplifiers are placed between max run strips to increase power from the end of one strip to the beginning of the next. This power boost helps to extend the run of multi-color LED strip lights. For single-color strips, you can add power further down the run.

See an example of how to use an amplifier in our cove lighting article.

If your project calls for very long runs or you may want to expand the circuit in the future, consider getting an additional constant voltage power supply. With multiple power supplies, you guarantee ample power for the strips in your project and allow you to expand your system anytime.

Disclaimer: LED strip lights generate heat when illuminated. Please do not try this at home.

Follow these steps to stop excessive voltage drop in your LED strip light installations.

If you would like a more in-depth look or for information beyond the scope of this article, see our Ultimate Strip Lighting Guide or contact us for customer support. Or, shop various AC/DC and DC/DC power supplies here.