Convoy T2 vs S2 UV brightness and runtime

LED Flashlights – General Info
1

I’ve been trying to buy a UV flashlight. I’ve seen good reviews of the S2 and S2+ but I haven’t seen any of the T2. A major problem with UV emitters is the high Vf, causing it to stop working when the voltage drops below ~3.7V, so you can effectively only use only less than half of the battery. The T2 is interesting in that it claims to support using AA, implying that it has a boost driver since there is no way to run a UV emitter directly with an AA cell. I intend to use 14500 cells, but I’m not sure how much this offsets the much smaller battery capacity. In addition, it is mentioned that it can only supply 540 mA with an 14500 cell, which makes me question the possible output levels. Can anyone with the T2 UV chime in?

2

A couple things that you should be informed about:

  1. Different UV emitters have different Vfs. While they are generally higher than those of white LEDs, many of them do function well below 3.7V.

  2. I’ve built a UV S2+ with the Seoul CUN66A1G emitter with a 4x7135 driver. Through even a crappy multimeter setup with more than 1m of test lead cable, I measured 1310mA at 4.18V down to 400mA at 3.59V, with almost linear decay in between. Actual current draw is higher due to test leads/poor contact. In fact, even with the reduced measurements, my light still draws 550mA at 3.71V, which is more than the 540 a T2 could manage.

If you want the most output for the usable battery life, S2+ should be a no-brainer. The advantage of the T2 is smaller size and potentially (as I don’t have the setup) more stable runtime, but IMO not worth it as the S2+ beats it in output at every battery level, more than doubling it at 4.08V+.

3

I’ve been out of it for a while, but the S2+ is great. Purple host, ZWB2 filter, what’s not to love?

Only I think it’s a bit overdriven, which isn’t great for longevity, so I limit myself to bursts not more than a minute or so.

4

Yeah UV emitters are generally much more fragile compared to white emitters. I’ve seen failures of the Nichia UV LED on the forum and heard of Seoul LEDs failing from Simon, but mine (Seoul CUN66A1G) is holding up well even after extended runs (had it about 2 years now). The official maximum current is 1400mA, so the 4x7135 driver is perfect for that.