LED Test / review EN
2023-06-11
In recent years, chinese-developed LEDs have increasingly been used in flashlights. This was primarily driven by reasons of lower price as well as changing conditions for international business. Nowadays, many a lamp has a Chinese LED. Nevertheless, it is usually completely unclear to what extent Western technology or manufacturing processes are used - a matter that this test will not clarify either. But we will see how well the GT-FC40 performs as a high-power LED with very high color rendering and whether the light color is really as good as some have already reported.
In addition, at least some electrical data about this LED, which is unknown in the end, are collected here, because there are still almost no clear informations about the electrical characteristics around…
- Type: multi-die
- Bin: unknown
- Color group: unknown (5000-5500 K)
- CRI: 90
- Rated voltage: unknown
- Max. Forward current: 4000 mA
- Max. Peak current: unknown
- Viewing angle: unknown
- Thermal resistance: unknown
- Max. Temperature Tj: max. 150 °C
It is to be noted that no reliable data for this LED can be found. I am also not aware of an official data sheet, so that the above mentioned data should always be with caution!
The GT-FC40 is a multi-die LED without dome (called domeless). The yellow luminous surface (LES) is divided into 16 segments, 4 of which are connected in a row (4S), resulting in the configuration 4S+4P in the internal wiring.
A clear layer of silicone covers the light area. The substrate is dark gray with small gold colored markings at the corners. The size format is 7070 (7.00 x 7.00 mm). It should be noted that there is probably a second variant of this LED around, which is for example used in the Convoy L6 - the edge around the light area is larger, resulting in seemingly larger dimensions (possibly 9090 = 9.00 x 9.00 mm).
There is no marking for anode/carthode on the top of the FC40 I tested here.
The symmetrical package allows the use of rotated centering aids or those for XHP LEDs without any problems.
The arrangement of the contacts in the footprint corresponds to that of the 12 V XHP LEDs, which means that LED boards for 12 V XHP LEDs can also be used. A small ‚missing corner‘ indicates the cathode.
Through the 16 segments there is a kind of “grid pattern”. The individual luminous surfaces are clearly recognizable due to the distinct bluish discoloration. The individual segments seem to be interconnected with small bonding wires, which, however, do not cover any part of the illuminated area or segments.it The light color with a CCT of 5000 K is achieved here by means of mixing the blue and yellow portions of the illuminated area.
The luminous area is 30.8 mm² in size. Accurate luminous area determination is more difficult than with a single-die emitter due to the segmentation.
The lack of bonding wires on the top of the die increases efficiency due to the lack of shading. The segmented LES makes this LED less suitable for focal optics or reflectors and, if good light quality is desired, requires the use of diffusing screens or specially textured orange-peel reflectors.
As with many emitters with multiple LES or segments, not all luminous segments illuminate evenly at extremely low currents. This is one reason why many manufacturers specify minimum operating currents: to ensure uniform illumination in lamps with many individual emitters.
Within official parameters, as far as known:
- at 4000 mA (official maximum current): 3871 lm @ 12.51 V
- Power at official maximum: 50.04 W
- Efficiency at 4000 mA: 77.4 lm/W
Due to the lack of official information on binning and maximum currents, the informative value of the data is limited. It is noticeable that the power at the specified maximum current of 4 A results in almost exactly 50 W.
Overcurrent:
- Maximum reached at 10.8 A, at this point 6503 lm @ 14.31 V
- Power at maximum 154.5 W
- Sweet spot at about 7 A (5626 lm @ 13.41 V)
- Power at sweet spot 94 W
- Efficiency at maximum 42.1 lm/W
- Efficiency in the sweet spot 59.9 lm/W
Operating this LED beyond the given maximum current is only worthwhile to a certain extent. At maximum possible current, the efficiency drops to 42 lm/W, a range that can already be achieved by highly selected halogen lamps under ideal operating conditions. (Even the commercial IKEA 20 W G4 halogen lamp reached nearly 36 lm/W before the filament melted).
Compared to the XHP70.2 in the 12V configuration, the GT-FC40 has a fairly low Vf, which is already in the range of the latest XHP70.3 (test to follow), which increases the efficiency somewhat, especially at higher currents. This shows once again why the MT-G2 - which is already more than 10 years old – is no longer used in flashlights, especially in OP reflectors, despite the still attractive light quality, and simply no longer corresponds to the current state of the art.
Values at 25 °C Tsp, at 85 °C Tsp values are 6-14 % lower
Due to the lower efficiency and therefore lower luminous flux, the luminance is significantly lower than that of the XHP70.2, especially since the size of the LES is very similar for these LEDs and therefore primarily the lower luminous flux comes into play.
Despite the highest binning available since, the MT-G2 simply has no chance at all. The light area is too large and the efficiency is way too low.
Despite the strong color differences which can be seen on the LES, the light image is usable in a standard reflector. Due to the segmentation of the luminous surface, there are cross-like artifacts in the light image, but a strong color distortion does not occur.
This is probably one of the reasons why some manufacturers also use this LED with a smooth (SMO) reflector. When using an OP reflector, the light image should roughly correspond to what can be expected from a lamp with MT-G2 or the first generation of XHP70.
Despite the specified color temperature of 5000-5500 K, my sample achieves a CCT of over 6200 K in the test. Nevertheless, this GT-FC40 lies almost perfectly on the blackbody curve, resulting in a pure white without color distortion. For lighting tasks where color fidelity and a “pure” white as possible are important, this LED is highly recommended. However, it is unclear to what extent there is a color dispersion depending on the classification into individual color groupings - without a data sheet or further information from the manufacturer, this aspect can hardly be evaluated.
- Ra: 96
- R9: 96
- CCT: 6335 K
- duv: 0,0005
The biggest advantage of the Getian GT-FC40 is without doubt the very good light quality. In addition, the use of smooth reflectors is possible in principle, although I advise against this in the sense of a good light pattern without artifacts or color distortions and recommend OP reflectors.
The performance is not very high, with variants with very high color rendering having significantly lower efficiencies. 5000 lumens from a package are quite possible here - assuming sufficient cooling - although other emitters are also to be preferred here with almost 100 W power in terms of efficiency and coolability.
Pro
- extremely good light quality
- compatible with 12V XHP boards and accessories (7070 version)
Neutral
- strong deviation from stated 5000-5500 K CCT
- only available in 12 V variant
- light pattern in reflectors expandable
- Luminance corresponds to XHP70.2
Contra
- low efficiency, low luminous flux
- no reliable information about the LED publicly available
- only available in China or from Chinese sellers
Thank you for reading the test. 
Greetings, Dominik