Voltage Drop in LED Strips: Why the Far End Is Dimmer and How to Fix It

Voltage drop is the loss of part of the supply voltage along the strip's copper traces and power cables due to their own electrical resistance. The longer a run fed from a single end, and the higher the current flowing through it, the more the voltage sags by the far end — the diodes there receive fewer volts and glow dimmer, while RGB strips also shift in color tone. The fix isn't a new strip, it's correctly calculating power feed points. In this guide, the ARTLED team explains the mechanism, gives a calculation formula, and lists ready-made solutions.

What Voltage Drop Is and Why It Happens

An LED strip is a flexible PCB with two copper traces (+ and −) to which groups of LEDs are connected in parallel every 2.5–5 cm. Current from the power supply enters one end of the strip and flows along these traces to every subsequent group of diodes. Copper has resistance, so by Ohm's law (U = I × R) a small share of voltage is lost on every centimeter of trace. The farther from the feed point, the more diodes have already drawn their current, and the remaining trace carries the accumulated resistance of the whole path already covered.

Main Factors Behind the Sag

✓ Run length from the feed point. Trace resistance grows directly with length — 10 m produces four times the voltage drop of 5 m at the same power.

✓ Operating voltage. At the same power, a 24V strip draws half the current of a 12V strip — and resistive losses scale with the square of current, so the drop falls roughly fourfold.

✓ Strip density and power. A 240-diode/m, 19.2 W/m strip draws twice the current of a 120-diode/m strip — and sags twice as much over the same length.

✓ Copper trace thickness. Strips with 2oz copper traces (70 µm) have roughly half the resistance of budget 1oz (35 µm) versions.

✓ Feed point placement. Feeding from one end produces twice the voltage drop at the far point compared to feeding both ends simultaneously.

How Many Meters You Can Feed From One End

Approximate limits for a standard medium-power strip (9.6–14.4 W/m) with no additional feed points:

How to Calculate Voltage Drop: The Formula

A simplified formula for estimating drop on a run fed from one end:

Example. A 12V strip, 14.4 W/m, a 5 m run fed from one end, trace resistance 0.15 Ω/m:

✓ Total power: 5 m × 14.4 W/m = 72 W

✓ Total current: 72 W / 12V = 6 A

✓ Drop: (6 / 2) × 0.15 × 2 × 5 = 4.5V — that's 37.5% of 12V, a visibly dimmer far end

✓ Fed from both ends, each half "sees" only 2.5 m — the drop falls to roughly 1.1V (9%), which is already visually unnoticeable

Actual trace resistance varies between ARTLED strip models — for an exact calculation for a specific project, ARTLED's team can size the feed points and cable gauge individually.

How to Fix Voltage Drop

✓ Feed from both ends. The simplest fix for 5–10 m runs — connect both ends of the strip to the power supply, so each half only "sees" half the distance.

✓ Power injection points every 5 m. A separate 0.75–1.5 mm² wire feeds power from the same PSU or a junction box at several points along the run — the strip's own traces no longer carry the entire load.

✓ Switch to a higher voltage. A 24V or 48V system at the same power draws 2–4 times less current — the drop falls proportionally.

✓ Several separate power supplies. Instead of one high-power PSU for the whole perimeter, use several smaller ones placed closer to each section — shorter cable runs mean smaller losses.

✓ Thicker feed cable. The resistance of the power cable itself between the PSU and the strip often causes more drop than the strip's own traces — use at least 1.5 mm² gauge for runs over 3 m.

Common Mistakes

Voltage drop is most often mistaken for a defective strip, and people try to "fix" it by replacing the strip — when the real cause is the power feed layout. Other common mistakes: feeding an 8–10 m run from one end instead of two, using thin wire (0.5 mm² or less) for feed cable runs over 3 m, installing a single central power supply for a 15–20 m perimeter instead of several distributed feed points, and not planning for 24V during the design stage of a long run.

Frequently Asked Questions

Can voltage drop be eliminated completely?
Not completely — it's a physical property of any current-carrying conductor. But it can be reduced to a visually unnoticeable level (under 5%) with the right choice of voltage, run length, and feed points.

Does voltage drop affect the strip's lifespan?
Indirectly, yes: the section near the feed point receives full voltage and runs at its rated limit, while the far end runs underpowered. This uneven load accelerates degradation specifically in the section closest to the PSU.

Can a dimmer compensate for voltage drop?
No — a dimmer only scales the PWM signal for the entire strip at once; it doesn't compensate for the voltage difference between the start and end of a run, so the brightness gradient remains.

How much better protected against voltage drop is a 48V system compared to 12V?
At the same power, a 48V system draws four times less current than a 12V system, and voltage drop scales with current — so losses over the same cable run fall by roughly 8–16 times.

Conclusion

A dimmer far end is almost always voltage drop, not a defective product or diode degradation. The fix belongs at the design stage: choosing the right voltage (12V, 24V, or 48V), feeding from both ends for runs over 5 m, and adding power injection points on long runs completely remove the brightness gradient.