When you’re shopping for a bike light, one of the first decisions you’ll face is whether to go with a self-contained light system or an external battery light system. Both have their place in a rider’s kit, and understanding the engineering behind each design will help you choose the right light for your riding style.
As a manufacturer that produces both types, we’re often asked: “Which one should I buy?” The answer isn’t about one being better than the other. It’s about matching the right tool to your specific needs.
Understanding the Two Designs
Self-contained light systems integrate the battery, LEDs, and electronics into a single unit. Everything you need is housed in one compact package that mounts directly to your helmet or handlebars.
External battery light systems separate the battery pack from the light head, connecting them via a pluggable cable. The battery typically mounts to your frame or sits in a backpack, while the lighter head unit goes on your helmet or bar.
Each design exists for good reasons. Let’s look at what drives these different approaches.
The Case for Self-Contained: Simplicity and Convenience
Cable-Free Setup
The most immediate benefit is the absence of cables. There’s no battery to attach separately, no wire to route, and no connections to worry about. You click the light onto the mount, pair your wireless remote, and you’re riding. Our testing shows it takes roughly half the time to mount a self-contained light compared to setting up an external battery light system.
For commuters rushing to work or riders who switch between bikes frequently, this convenience is significant.
Cleaner Cockpit and Low Profile
If you’re bar mounting your light, a self-contained system keeps your handlebars tidy without additional cables alongside your brake lines and other accessories. The design works seamlessly with GoPro and quarter turn mount options for integrated over/under combo mounts.
For helmet mounting, self-contained light systems offer a lower profile with less chance of catching on a branch during technical trail riding. Our Gloworm CX Core Light System comes with a low profile helmet mount adapter as standard, designed specifically to minimise profile while maintaining secure attachment.
Fast Charging for Real-World Use
Modern self-contained light systems like our Gloworm CX Core use USB-C fast charging technology. You can go from completely flat to fully charged in under 1.5 hours. If you forget to charge your light and realise it on your way out the door, a quick 15 minute charge will give you enough runtime to get to work and back.
This fast turnaround also suits riders who do multiple short rides in a day or week, rather than single long expeditions.
Flexibility Through Power Pack Compatibility
While the integrated battery provides excellent runtime for most rides (our Gloworm CX Core delivers 80+ minutes at maximum 1,750 lumen output) you’re not locked into that runtime. Pass-through charging via a Gloworm Power Pack G2.0 gives you the flexibility to extend your runtime for multiday bikepacking missions, delivering up to an additional 4 hours at maximum power.
App Control and Customisation
Self-contained light systems offer smartphone app compatibility through the Gloworm Link mobile app, allowing you to fine-tune runtime by adjusting output levels and customise flashing modes for visibility when commuting in traffic.
The Case for External Battery Light Systems: Maximum Performance
Form Factor Efficiency and Extended Runtime
When you separate the battery from the light head, each component can be optimised for its specific function. The Power Pack is shaped for maximum capacity, while the light head is designed purely to maximise heat dissipation and efficiently place the LEDs. This results in a much smaller, lighter form factor on your handlebars.
Because you’re not constrained by integrating the battery into the light head, you can use much larger capacity Power Packs. Our Gloworm X2 Lightset (G2.0) provides 4 hours runtime at its maximum 2,000 lumen output. For riders doing long night rides, multi-hour endurance races, or technical trail riding where you need sustained high output, this extended runtime becomes essential.
Battery Fast Charging Technology
Our external battery Power Packs support fast charging via USB-C, meaning you can quickly top up between rides or get back out on the trail sooner after a full discharge.
Superior Weight Distribution
For helmet mounting, external battery light systems offer a significant advantage in weight distribution. The light head itself is considerably lighter, often less than half the weight of a self-contained unit. This reduced weight on your head means less neck fatigue during long rides and better balance, particularly when looking down at technical trail features.
The Power Pack sits in a pack or on your frame, placing the weight closer to your centre of gravity.
Higher Lumen Output Options
External battery light systems can deliver higher maximum output because the larger Power Pack can support the power draw, and the separate light head has more surface area dedicated to heat dissipation. Our Gloworm XSV Lightset (G2.0) (our most powerful light) delivers 3,600 lumens with 2 hours runtime at maximum brightness, ideal for high-speed technical descents or wide open terrain.
App Control and Low Profile Design
Like our self-contained lights, all external battery light systems feature smartphone app compatibility through the Gloworm Link mobile app, allowing you to fine-tune runtime and customise output settings. The light heads also use low profile mounts, combining the benefits of reduced helmet weight with a streamlined, snag-free setup.
Matching Light Type to Riding Style
Choose Self-Contained If You:
- Commute regularly and need a light that’s quick to charge and mount
- Switch between bikes frequently and want hassle-free setup
- Ride 1 to 2 hours at a time, where integrated battery capacity is sufficient
- Value simplicity and want minimal cables and components
- Mount on your helmet for trail riding and want a low profile setup with minimal setup time
- Occasionally need more runtime but can use a Power Pack when required
Our recommendation:
The Gloworm CX Core Light System delivers 1,750 lumens with 80+ minutes at maximum power, extending to up to 10 hours at lower settings. With USB-C fast charging (under 1.5 hours) and optional Gloworm Power Pack compatibility, it’s ideal for commuters and riders who value convenience without sacrificing performance.
Choose External Battery Light Systems If You:
- Ride for 2+ hours regularly and need extended runtime at high output
- Race endurance events or do bikepacking trips where maximum runtime is critical
- Need maximum light output for high-speed or technical riding or wide open terrain
- Want the lightest possible helmet mount with weight distributed away from your head
- Prefer a one bike setup that stays configured rather than swapping lights between bikes
Our recommendations:
- For balanced performance: The Gloworm X2 Lightset (G2.0) offers 2,000 lumens with 4 hours runtime at maximum brightness, perfect for serious nocturnal adventures
- For maximum output: The Gloworm XSV Lightset (G2.0) leads with 3,600 lumens and 2 hours runtime at maximum brightness, changing the way you ride at night
The Middle Ground: Modern Flexibility
The gap between these two types has narrowed considerably. Self-contained light systems now offer impressive runtime and the option to add external battery capacity when needed through Gloworm Power Pack G2.0 compatibility. External battery light systems have become lighter and more streamlined, with improved weatherproofing and reliability.
Many riders run both types depending on the ride. A self-contained light system might live on the commuter bike for quick daily rides, while an external battery light system stays configured on the mountain bike for longer trail sessions.
Runtime Reality Check
When comparing lights, pay attention to runtime figures at the actual output levels you’ll use. A light that claims “10 hours of runtime” but achieves that only at 200 lumens won’t help you on a fast night ride where you need 1,500+ lumens.
For reference:
- Gloworm CX Core Light System: 80+ minutes at maximum 1,750 lumen output, up to 10 hours at lower settings
- Gloworm X2 Lightset (G2.0): 4 hours at maximum 2,000 lumen output
- Gloworm XSV Lightset (G2.0): 2 hours at maximum 3,600 lumen output
All our G2.0 lights feature Gloworm Link mobile app compatibility, allowing you to customise your light output to fine-tune your exact runtime requirements
Universal Mounting Options
Both light types benefit from Gloworm’s universal mounting system. Our Gloworm Universal Light Mount and Gloworm Universal Helmet Mount options give you flexibility to adapt your setup as your riding changes. The Gloworm CX Core comes standard with helmet mounting options, with an optional CX Core Bar Mount Upgrade available, that includes a wide beam optic specifically optimised for handlebar use.
The Bottom Line
There’s no universal “best” bike light type. Our Self-contained light systems excel at convenience, quick charging, and clean installation, making them ideal for commuters and rides of 2 hours or less. External battery light systems provide longer runtime, higher potential output, and better weight distribution for helmet mounting, making them the choice for endurance rides and situations where you need maximum performance.
Consider your primary riding style, typical ride duration, and whether you value convenience or maximum runtime. Many riders eventually end up with both types, using each where it makes the most sense.
Whatever you choose, the most important thing is having reliable light when you need it. Both designs will get you home safely.
Ready to find your perfect light? Browse our complete range of mountain bike light systems and accessories.