Acebeam was kind enough to provide me with a K1 in teal for review.
What’s in the box
The K1 is delivered in cardboard packaging with a viewing window.
The package contains the following:
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Flashlight
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14500 Li-ion battery with USB-C port
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USB-A to USB-C cable
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Lanyard with Acebeam branding
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Replacement O-rings
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User manual
Here are the specifications according to the user manual
Finish
As usual with Acebeam, the workmanship is excellent. The AL6061-T6 housing feels quite solid, has no sharp edges, and the hard anodization was flawless upon delivery.
The magnetic rotary ring for mode selection and the metal rear switch move smoothly and without any play. The rotary ring even has a sealing ring on the underside, which is presumably intended to prevent dust or sand from collecting underneath, causing creaking and wear.
The K1 can be disassembled into just two parts without tools: the battery tube and the head. The clip is attached with two TORX screws, the bezel appears to be glued on, the battery tube is milled from a single piece and therefore has no tail cap, and the mechanical rear switch appears to be pressed in. Overall, the K1 does not appear to be particularly maintenance-friendly, but this should not matter to more than 99% of users.
The clip is sturdy and the housing underneath has no knurling, so the lamp can be easily attached to the clip.
The emitters are protected by a non-tempered glass pane.
There is only a spring on the switch side. On the driver side, there is only the positive pole as a pin and another pin for reverse polarity protection. The driver itself is covered with a type of rubber, protecting it from damage.
The lamp is waterproof up to 2 m in accordance with IP68 and is designed to withstand drops from a height of 1.5 m. Since it does not have an integrated USB port, I have no doubt about its water resistance. Instead, it is used with rechargeable batteries with an integrated charging option. For EDC lamps, I prefer this solution in favor of increased robustness.
Power supply
The Acebeam K1 is an omnivore and likes anything between 1.2 and 4.2 volts. It can therefore be operated with alkaline primary cells, NiMH rechargeable batteries, or Li-ion rechargeable batteries.
The included battery is an Acebeam AB14CP10 USB-C rechargeable battery with date code 25-A8. It was delivered with 4.13 V, which is unusually high for a transport voltage. I subjected the battery to a capacity test using a Vapcell S4+ at a discharge current of 500 mA. It delivered 881 mAh. That is about 12% less than the rated capacity and corresponds to what I otherwise measure for cells with a rated capacity of 900 mAh. In fact, the measurement result is almost exactly the same as for my older Acebeam ARC14500 Type C with a nominal capacity of 920 mAh, which came with my Acebeam Rider RX. It seems to me that the same cell is hidden under the wrapper.
The battery can also be charged using a USB-C to USB-C cable with PD protocol. I measured a maximum charging power of 2.8 W and 560 mA charging current. This means that the battery takes quite a long time to fully charge, but it protects the cell chemistry and increases the service life.
There is no need to worry about deep discharge due to non-use: the rear switch is mechanical, so there is no parasitic drain. However, the K1 does not have deep discharge protection. Therefore, only protected 14500 cells should be used, and NiMH batteries should not necessarily be used until they are completely depleted.
The flashlight does not provide any information about the battery level.
Size comparison
One criticism of the K1 is definitely its size. Although it is basically a small and compact flashlight, it is quite large compared to other 14500 flashlights. In fact, even with the same maximum diameter, it is 10 mm longer than the Sofirn SC32, which also has a rear switch but an 18650 battery with more than three times the capacity (unfortunately, I no longer own this flashlight, so I was unable to take a comparison picture). To be fair, however, it must be said that lamps with mechanical tail switches are longer than those with electronic tail switches or side switches due to their design.
Here are a few lamps in comparison. The Sofirn on the far left is only included as an example. It has a 21700 battery with more than five times the capacity of the Acebeam K1.
Sofirn IF25 (21700) | Acebeam K1 | Acebeam Rider RX | Lumintop Tool AA 2.0 | Wurkkos HD12
Overall, in my opinion, the size is neither here nor there. For a 14500 lamp, it is surprisingly large. I would prefer it if the battery tube were 4 mm thicker and a little longer and if it housed a significantly more powerful 18650 battery instead.
Operation (UI)
The K1 fits very well in the hand thanks to its deep knurling and length, and has a lot of grip. It is also very easy to operate even when wearing gloves. The selector ring can also be used easily with one hand, making one-handed operation possible without any problems.
The mechanical rear switch is designed as a forward clicky and allows momentary lighting. This works very well and intuitively, and the pressure point is very comfortable. To switch it on permanently, you have to press the switch in about 3 mm. Due to the resistance and stroke, I consider accidental switching on in your pocket to be quite unlikely, despite the exposed switch. It has mode memory and the lamp always starts in the last mode used. However, it should be noted that the switch or the driver behind it has a relatively long input delay. I would estimate it to be around 100–200 ms. In practice, this does not play a major role, but if you pay attention, you will notice it.
Since the threads are anodized, it can be mechanically locked out by turning the head 1/4 turn.
In my opinion, the combination of selector ring and button is the optimal solution for lamps with different emitters. This allows you to switch between modes very easily, quickly, and without complicated click sequences. In addition, there is no need to compromise on the number of light levels. This is a really great solution and makes it a lot of fun to use. Incidentally, the brightness levels are retained when changing modes. If the lamp is switched on at the highest level with white light and you switch to UV light, the highest level is also set there.
The lamp even has a strobe mode. However, I consider this to be useless in practice, as it cannot be reliably accessed in an emergency situation. To activate it, you have to use the selector ring to select the middle mode and quickly turn it back to the white light. And you have to do this within 0.3 seconds. If you turn it too far, the strobe will not start. In a hectic emergency, this is unlikely to work very well. Switching quickly between the left and right stops would probably be the more reliable option here.
It has different numbers of brightness levels depending on the mode. There are three for white light, two for UV light, and only one for the laser.
Beam and performance#
When using white light and a 14500 battery, the K1 uses a linear driver; when using AA cells, it uses a boost driver. This results in good control for a lamp of this size.
The brightness of all light sources is naturally lower with AA batteries than with Li-ion batteries.
In the white wall shot with the white LED, a slight dent in the spill can be seen. This is caused by the bezel on one edge of the reflector. However, this is not visible outside of a white wall.
Overall, it delivers a very clean light image without any annoying artifacts. Due to the LED, the CRI is likely to be <70, but this is not particularly bothersome for a lamp of this type. At 6500K, its light color is very cold, but without a blue cast. My personal sweet spot is 5700K.
I could only detect PWM at the lowest level, and even then it was at a very high frequency, so it is not visible to the naked eye. This can be seen here in the close-up of the Cree XP-LR based on the many horizontal lines.
I find it amazing how much range the round domeless XP-LR delivers in the smooth reflector of this small lamp! According to the manufacturer, it is 12,400 cd at 1000 lumens, which is a cd/lm ratio of 12.4. Personally, I like the range between 12 and 15 best for general use. According to ANSI, this achieves a range of 223 m, which corresponds to a little more than 100 m of actual usable range in practice.
The same beamshot settings as always for me: 1/8 s | F/4.0 | ISO 6400 | 24 mm (FF)
In the close-up, you can see that the LED is not perfectly centered. However, I couldn’t see any effect on the photo. Perhaps round LEDs are more forgiving than square ones.
The type of UV LED used is not known in detail. However, it has a power of 1000 mW and a wavelength of 365 nm.
Switched off
Switched on
The performance data is excellent, and it is ideal for highlighting security features on ID documents or banknotes. It can also be used to quickly detect soap residue in the bathroom.
The green laser is not specified in detail, but in my case it has a cleanly centered beam and a usable range of over 100 meters.
At too great a distance, the dot becomes too small to be seen from afar. It is therefore quite powerful and should not be used carelessly outdoors.
Unfortunately, you can’t see much of the emitter in the close-up
The laser was not visible with my standard beamshot settings, so here is a picture 4 stops brighter than usual:
1/8 s | F/4.0 | ISO 102,800 | 24 mm (FF)
However, it is unclear how powerful it really is. In addition, the housing is labeled as laser class 1. The user manual, product page, and other images on the Internet indicate class 3R. When I inquired with the manufacturer, they replied that the US model is class 3R and the EU model is class 1 and complies with EU requirements.
Conclusion
Positive
- Exemplary workmanship
- Highly multifunctional thanks to three different emitters
- Excellent operating concept with selector ring and rear switch
- Powerful white light with long range
- UV light with 365 nm
- Powerful green laser
- Can be used with AA and Li-Ion batteries
- Robust and non-slip housing
Neutral
- Cold white light with a low CRI
- Strobe mode not fail-safe
Negative
- The switch has quite a large input lag
- Battery does not reach its rated capacity
- Very large for a 14500 lamp
Really great lamp that I like to have with me. If it were slightly larger than 18650 with neutral white light, it would be perfect for me!
