LEP flashlights are either something to play around with (but not for children!) or are used in very specific situations where a very narrow, long-range beam of light is required.
The Vastlite Versa Bow can not only shine far but, thanks to the integrated zoom mechanism, can also produce a wide beam if needed. With its compact size, it also fits comfortably into your pockets.
You can find the German version of this review on my website: SammysHP Blog › Vastlite Versa Bow
The flashlight was kindly provided to me by flashlightgo for this review. The online store, based in China, offers a wide selection of flashlights from various manufacturers and ships worldwide.
Overview
The Versa Bow is delivered in a black box with a subtly patterned surface.
- 21700 Li-ion battery (5000 mAh, unprotected, flat-top, 3.65 V at arrival)
- USB-C charging cable
- 2x replacement o-ring
- Manual (EN, CN)
The manual summarizes the technical specifications and operation of the flashlight in concise terms and is easy to understand.
One advantage of LEP flashlights is that they don’t require a large head to achieve impressive range. This makes the Versa Bow easy to fit into a jacket pocket and even a pants pocket.
Length: 128 mm
Diameter (head): 35.3 mm
Diameter (battery tube): 25.5 mm
Diameter (tailcap): 28.0 mm
Weight (without battery): 109 g
Weight (21700 battery): 67 g
Weight (total): 176 g
In the comparison image, the Versa Bow is indeed the longest, but it also has the largest battery. Those who prefer something really small and compact should take a look at the Vastlite Minima Bow.
In addition to black, the flashlight is also available in orange and “sand” (a beige-gray color). The slightly matte anodizing prevents fingerprints from showing on the surface.
On a flat surface, the flashlight is hardly stopped from rolling away. Only the button protrudes enough to be pressed, which can cause the flashlight to turn on unintentionally.
The front part of the head, from the area with the labeling to the small, circular dimples, can be rotated. I will discuss the zoom mechanism later. There are four grooves, each about 2 × 8 mm in size, which can be used for glow sticks.
The battery tube has a deep, spiral pattern, ensuring a secure grip even in wet conditions. Curved lines give the impression that the tube has a waist, but in reality, it has the same diameter throughout.
The flashlight does not come with a clip. However, there is a hole on the tailcap where a strap or lanyard can be attached.
The tailcap also contains a strong magnet, allowing the Versa Bow to be attached to magnetic surfaces. However, I can’t immediately think of a scenario where this would be useful for an LEP flashlight, which produces a very narrowly focused beam.
The magnet can be easily removed if needed by unhooking the spring with a pointed object. To support the spring afterward, the cavity must then be filled with something.
The Li-Ion battery can be charged directly in the flashlight via a USB-C port. During charging, the status LED on the button blinks red and once charging is complete, it lights up green.
The port is protected against dirt and water by a small silicone cover. It seems to do its job well, but it is in a very exposed position, which creates a certain risk of it being accidentally opened.
The battery charges at up to 2 A – though not continuously, but with short interruptions. At the end, the charging process finishes at 1.5 A.
I suspect that a 2 A linear regulator is used, with the charging periodically interrupted to measure the battery’s open-circuit voltage. After about 75 minutes, under load the battery reaches a voltage (5 V input minus the regulator’s dropout) at which the regulator can no longer supply the required current. Once the battery’s open-circuit voltage reaches the target of 4.20 V, charging is terminated.
Further measurements would be needed to confirm this, but at least it would be a plausible explanation for the observed behavior. This is not an allowed charging method for Li-ion batteries, as the maximum voltage is exceeded.
According to the manufacturer, it uses two LR5112 in a parallel, which according to the specifications should be suitable. However, my observations do not match the description in the datasheet, so there may be an error in the implementation. The battery voltage should not exceed 4.20 V. In addition, the charging process is restarted multiple times at the end (the status LED turns green in between). Interruptions of the charging process are neither useful nor intended for the charging controller.
Thanks to the springs on both ends – with the spring on the driver side being very stiff – all types of 21700 Li-ion batteries are supported.
Zoom flashlights are often only moderately water-resistant, as zooming changes the flashlight’s volume and can draw air inside. In contrast, the internal zoom mechanism of the Versa Bow allows for “protection against continuous submersion” according to IP68. It is also supposed to withstand drops from up to one meter.
User interface
The Versa Bow is operated via a side button made of plastic with a slightly concave surface.
The UI is well-designed and easy to understand. Two brightness levels with mode memory are available, each of which can also be accessed directly via its own shortcut.
| State | Action | Function |
|---|---|---|
| Off | 1 click | Turn on in previously used brightness |
| Off | 2 clicks | High |
| Off | 3 clicks | Strobe |
| Off | 4 clicks | Lockout |
| Off | 5 clicks | Turn locator LED on/off |
| Off | Hold | Low |
| On | 1 click | Turn off |
| On | 2 clicks | High |
| On | 3 clicks | Strobe |
| On | Hold | Change brightness (Low/High) |
| Strobe | 1 click | Turn off |
| Strobe | 2 clicks | High |
| Strobe | 3 clicks | Switch between Strobe/SOS/Beacon |
| Lockout | 4 clicks | Unlock and turn on in previously used brightness |
| Lockout | Hold | Momentary Low |
In addition, there is a strobe group containing an 8 kHz strobe, an SOS and a beacon with an interval of about two seconds. Unfortunately, the selected strobe mode is not retained after the flashlight is turned off.
The button contains a status LED that glows solid green when the flashlight is off, making it easier to locate the button in the dark. It is only visible in complete darkness, but consumes almost no power (just 22 µA). It can still be turned off with five clicks.
Illumination
White LEDs (light-emitting diodes) are typically made from a blue LED coated with a phosphor layer. This layer converts parts of the blue light into other wavelengths, making the emitted light appear white to the human eye. A challenge with this technology is heat dissipation: small LEDs can only dissipate a limited amount of heat, which restricts their maximum brightness. Conversely, if an LED is designed to be particularly bright, it needs to be larger, making it more difficult to focus its light into a tight beam.
LEP stands for “Laser Excited Phosphor” and describes the underlying principle: a blue laser is directed at a phosphor layer, creating a small, intense point of white light. Because the laser and the phosphor layer can be cooled separately, it’s possible to achieve a very small light-emitting surface with high intensity.
Currently, there are two common methods for implementing an LEP module: either the laser beam hits the phosphor layer from the front (sometimes with the help of a small mirror), or the laser is positioned behind the layer and shines through it – as is the case with the Versa Bow. A collimator lens then focuses the light into a tight beam.
A highlight of the Versa Bow is its zoom mechanism, which allows the width of the beam to be continuously adjusted by turning a ring on the head.
The mechanism is fully integrated inside the flashlight and protected by a glass with a greenish anti-reflective coating. The adjustment range from stop to stop is just under one full turn.
In the fully focused state, the Versa Bow produces a very narrow spot with a diffuse edge and a cool, slightly yellowish tint. When zoomed out, a bluish center and a yellow outer ring appear.
The color gradient becomes particularly noticeable from the side. It should be noted that an LEP flashlight like this is optimized for maximum range rather than light quality. And a zoom function does not make it better.
Anyone looking for an LEP flashlight has a very specific use case in mind. Fully focused, it produces a “pencil beam”. Like a lightsaber. A narrow streak of light dancing across the landscape. The zoom function makes the flashlight somewhat more versatile, but “floodlight” does not mean truly floody. Even at its widest setting, only a narrow circle is illuminated.
Driver and runtime
Unlike reflector-based flashlights, only the light that hits the lens is utilized. As a result, brightness varies depending on the zoom setting.
| Mode | Brightness ¹ ⁴ | Runtime ¹ | Intensity ¹ (Throw ²) | Current ³ |
|---|---|---|---|---|
| High | 320 lm 400 lm |
3 min + 5:30 h | 361 000 cd (1200 m) |
3.20 A |
| Low | 60 lm 80 lm |
7 h | 0.65 A | |
| Off | 34 / 56 µA ⁵ |
¹ According to manufacturer ² ANSI FL1 ³ Measured
⁴ Spot / Flood ⁵ without/with status LED
On low, brightness remains constant for most of the runtime. On high, it gradually decreases until the thermal regulation kicks in once the head reaches around 50 °C. Depending on cooling, this allows about five continuous minutes at full brightness.
My measurements suggest that the driver is a linear regulator. Using an oscilloscope, a minimal ripple can be detected, but no PWM. Below a battery voltage of about 3.25 V, the LED in the button starts blinking red. When the voltage reaches approximately 2.95 V, the flashlight automatically shuts off to protect the battery from deep discharge.
Conclusion
The Vastlite Versa Bow is a compact LEP flashlight with a convenient zoom mechanism. This extends its use beyond a narrow “pencil beam” and also allows for close-range operation. As typical for LEP flashlights, the beam exhibits a slight color fringe, which is particularly noticeable in the flood setting.
The implementation of the charging function is not particularly great: apparently, the Li-ion battery is being charged with an improper method, which could shorten its lifespan or even cause damage.
Got curious? Check out the Vastlite Versa Bow at flashlightgo.
