2024-07-09
- Type: lateral, single-die domed
- Bin: G2 (min 720 lm @ 1,500 mA 85 °C)
- Color group: BA (6500 K)
- CRI: 70
- Rated voltage: 2.7 - 3.3 V
- Max. Forward current: 3,750 mA
- Max. Peak current: 5,000 mA
- Viewing angle: 120 °
- Thermal resistance: 1.2 K/W
- Max. Temperature Tj: max. 150°C
Datasheet can be downloaded here: SST-25-WES, 2.2 MB
The SST-25 tested here was purchased from Kaidomain in June 2024. Many thanks to BLF user @INeedMoreLumens for providing the LED tested here!
In principle, the SST-25 is very similar to the well-known SST-20. The LED chip, which is covered by a silicone dome, is manufactured in the classic lateral design, with bonding wires ensuring the connection of the anode. In the past, this has often led to total failures during such overcurrent tests.
The most important advantage of this technology is the lack of side emitting light from the LED chip. Earlier LEDs were almost exclusively constructed in this way. The 3535 footprint corresponds to that of the SST-20 and the symmetrical housing means that the standard accessories can be used for the 3535 footprint.
The illuminated area is 5.8 mm² in size. The bonding wires are connected at two corners, which means that the illuminated surface is not completely symmetrical. However, this should not cause any problems in optics. Similar to older Cree LEDs (XP-G2), the illuminated surface is covered with small, darker dots.
- at 3,750 mA (official maximum current): 1614 lm @ 3.56 V
- Power at official maximum: 13.5 W
- Efficiency at 3,750 mA: 119.2 lm/W
- Maximum reached at 7.4 A, at this point 2243 lm @ 4.29 V
- Power at maximum 31.7 W
- Efficiency at maximum 70.7 lm/W
Data for 25 °C Tsp (at 85 °C the luminance values are around 13 % lower).
The SST-25 is quite efficient - especially for the older lateral design. However, the Vf is very high, which can be a problem for FET-based (unregulated) drivers, especially at higher operating current. In order to utilize the maximum performance of this LED, a boost driver must be used.
The SST-25 was not damaged during the test. There was no significant increase in the forward voltage - which indicates imminent failure due to destruction of the bonding wires. Nevertheless, prolonged operation close to the maximum is not recommended, although the increase in luminous flux from around 6 A is limited anyway. More than 5 amps is not recommended for this LED.
The luminance is appropriate for an LED with such a large LES, so there are no surprises.
The beam is fine. There is a slight yellowish ring around the spot due to yellowish-green discoloration as the viewing angle increases, which looks clearer in the picture than it actually is. Depending on the optics and focus, however, this could be largely eliminated.
The spectrum corresponds to that of a cool white LED with low color rendering. The tint is greenish, but is still just within the ANSI color space. As is typical for Luminus, the tint shift is enormous as the operating current increases, so the SST-20 and SST-25 do not differ in this respect.
- Ra: 70
- R9: -32
- CCT: 7068 K
- duv: 0.0047
Summarized: the SST-25 is basically a more powerful version of the older SST-20, which can be operated with a higher current. The LED chip is larger and the thermal resistance has been reduced. However, the Vf is very high and the Luminus-typical tint is quite green at low operating currents, although the color group BA is pretty much exactly on the BBL.
It is likely that this LED will gradually appear in more and more flashlights in the future, especially as the footprint is identical to the SST-20 and there is no need to adapt LED boards and/or optics. In addition, the pricing is likely to be very attractive, especially for larger quantities, which should encourage rapid distribution among flashlight manufacturers, like known from SST-40 and SST-20.
Thank you for reading this test. 