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How Long Should Your Headlamp Last in a 100-Mile Ultramarathon?

  • Writer: TheTallNomad .
    TheTallNomad .
  • Jun 13
  • 3 min read

Running a 100-mile ultramarathon means facing extreme terrain, unpredictable weather, and—critically—long hours in the dark. Whether you're chasing a sub-24-hour buckle or grinding it out past 30 hours, your headlamp is one of the most important pieces of gear you’ll carry. Here’s how to make sure it lasts the full distance—and keeps you moving strong all night long.

🌘 How Many Hours of Darkness Will You Actually Face?

Most 100-mile races start early in the morning (around 5–7 a.m.). That gives you around 12–14 hours of daylight. For most runners, night begins in the back half of the race—and lasts 10 to 14 hours depending on pace and time of year.

  • Sub-24-hour runners: Expect ~7–9 hours of darkness

  • Average finishers (~28 hours): 10–12 hours

  • Winter races or >30-hour finishes: 13–14+ hours of darkness

Planning for 12 hours of reliable light is a safe bet for most.

🔦 How Bright Does Your Light Need to Be?

The right brightness depends on your terrain. Too dim, and you risk a fall. Too bright, and you waste battery—and your eyes can fatigue faster.

Terrain

Ideal Lumens

Notes

Smooth trail/fire road

100–150 lm

Conserve battery on easy stretches

Technical singletrack

200–350 lm

Optimal for roots, rocks, uneven terrain

Steep descents or nav

400–600+ lm (brief bursts)

Use “boost” modes when needed

A steady 200–250 lumens is ideal for most trail conditions during a 100-miler.

🔋 How Long Should Your Headlamp Last?

Let’s do the math. If you're running 12 hours at 200 lumens, you need at least 2,400 lumen-hours of battery power. Here’s what the best ultra-running headlamps offer in real conditions:

Top Headlamp Picks for 100-Milers (2025)

Headlamp

Runtime @ ~250 lm

Features

BioLite 800 Pro

8.5 h regulated + 8 h reserve

USB pass-through lets you charge while moving

Petzl Nao RL

9–12 h in Reactive Lighting (avg 250 lm)

Lightweight, swappable R1 battery

Fenix HM65R-T V2

10 h @300 lm

Dual-beam, rugged, uses 18650 battery

Petzl Bindi (backup)

2 h @200 lm

Featherlight emergency option

💡 Pro Tip: Cold weather can reduce battery life by 15–30%, so plan accordingly for mountain races.

✅ The Smart Ultra-Runner’s Lighting Checklist

Here’s how to ensure you’re covered from sundown to sunrise:

1. Target Runtime

Plan for 12 hours of continuous runtime at 200 lumens:200 lumens x 12 hours = 2,400 lumen·hours

2. Primary Headlamp

Use a headlamp rated for at least 8–10 hours at 200–250 lumens. Choose one with regulated output so it doesn't dim as the battery drops.

3. Backup Strategy

  • Carry a charged spare battery, or

  • Bring a second lightweight headlamp (e.g. Petzl Bindi)

4. Charge While You Run (Optional)

Use a pass-through USB cable and a 5,000 mAh power bank (~110g) to extend runtime without stopping.

5. Redundancy is Safety

Many races require two lights. Your backup isn’t optional—it’s life insurance when things go sideways at mile 83.

🧠 Field-Test Everything

Never trust packaging claims. Test every setting on long night runs in training, especially in cold or wet conditions. Know exactly how long your setup lasts in race-like conditions.

Final Thoughts

Lighting isn't just about visibility—it’s about performance, confidence, and safety. The right setup lets you bomb descents at 2 a.m., keep your rhythm on exposed ridgelines, and handle navigation when your brain is fried. Don’t wing it. Plan like a pro and light up your 100-miler with strategy.

Author: Andrew Hey CEO, Entrepreneur, Ultra Strategist, Helping high-performers train, race, and live at elite levels.

🔗 Share this article with your crew, and drop a comment if you want a gear list or real-world reviews of top lighting systems. Let’s get you across that finish line—fast, focused, and fully lit.


 
 
 

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