4 Cree Light !!

[Steve L]

I was hoping I could use 18650's. 350 mA is weird, since everyone else reports 950 mA. That can't be right. :thumbsdow

That doesn't sound right at all. At 8.4v (fully charged-best case scenario) X 350 ma = 2.94watts / 4 = .735 watts per LED. At 950ma X 8.4v = 7.98w / 4 = 1.995 watts per LED, much better. These numbers do not take into account circuit losses(the actual watts per LED will be less).

 

[wasBlinded]

I like this light, it seems very well made for a mere $50. It isn't as bright as I would have expected from four good Crees, even being driven at a mere 500 mA each, which is what I calculate the stock driver circuit is doing.

I've ordered a Shark+Remora board from the Sandwich Shoppe so I can drive all four in series at 1000 mA on high. This should be OK for short periods hand held, or continuous use on the bicycle where air flow should keep it cool enough.

Hopefully I'll then have an impressively bright $100 light with a less frustrating user interface.

 

[Photon_Whisperer]

In fact, it's easy to unscrew the whole heatsink with leds glued on an driver inside

How did you unscrew it? By applying torque on the springs? Did you have to drill holes on the heatsink? Mine have some heatsink glue on the threads and are tight.

 

[freshmaker]

I like this light, it seems very well made for a mere $50. It isn't as bright as I would have expected from four good Crees, even being driven at a mere 500 mA each, which is what I calculate the stock driver circuit is doing.

I've ordered a Shark+Remora board from the Sandwich Shoppe so I can drive all four in series at 1000 mA on high. This should be OK for short periods hand held, or continuous use on the bicycle where air flow should keep it cool enough.

Hopefully I'll then have an impressively bright $100 light with a less frustrating user interface.

What are your plans for heat dissipation?

It seems to me that there might be a small market for an emitter board that incorporated the circuit path with more metal and more subsequent heatsinking .

 

[Photon_Whisperer]

What are your plans for heat dissipation?

It seems to me that there might be a small market for an emitter board that incorporated the circuit path with more metal and more subsequent heatsinking .

I think it's possible to drive the LEDs at 1A/ea if you just fill in the void between the module base and the tube head with thermal adhesive. There's a lot of surface area there that's just wasted. Most of the heat has to be conducted through the threads which doesn't transfer much it seems.

 

[Jazchau]

Hello all,

I've been reading this thread since I ordered this light from DX about 3 weeks ago. I finally received it yesterday and been playing with it using the different battery options. I noticed it is a lot brighter with 4x RCR123 vs. 2x 18650. So I decided to run it through the bench DC power supply to see what its V-I curve looks like. Below is a graph that reveals some interesting aspects of this light's performance.

From the graph, the take-away is:

1) To get the full brightness, you need to feed it 10V or higher. Above 10V the regulation is pretty flat at about 7.7W.

2) Below 10V the brightness takes a huge dip. The current went from 0.77A to 0.12A !!!

3) Between 10V and 8V this light not so hot, with the worst brightness at just below 10V. This explains why the brightness is disappointing with 2 fully charged 18650's at 8.2V.

4) At 8V the light flickers.

5) Below 8V there's no regulation at all and the brightness drops off linearly with decreasing voltage.

Hope this helps to shed some light on this topic.

 

[Mike Painter]

Hello all,

2) Below 10V the brightness takes a huge dip. The current went from 0.77A to 0.12A !!!
Hope this helps to shed some light on this topic.

Interesting, justr a few post above we have someone saying there is little differences between batteries and reading through all of them we can get WOW to ho-hum.

Something isn't right.

 

[dda]

I have two of these lights in black. One has the yellow base LEDs and one has the newer silver base LEDs. Both lights draw 950 ma on freshly charged 18650 batteries and 550 ma on freshly charged 123s. I can tell a little difference in brightness between the 2x18650 and 4xrcr123s but very little. When using the same battery configuration in both lights, the brightness appears to be equal between the two lights. When shined on a white wall one of the lights has a slightly purple tint and one a slightly blue tint. When shined separately, both lights appear to be white. I use magnet discs on the + end of the protected 18650s to make sure I get good contact.

 

[Photon_Whisperer]

Interesting, justr a few post above we have someone saying there is little differences between batteries and reading through all of them we can get WOW to ho-hum.

Something isn't right.

I'm thinking they may have made an undocumented change with the boards like they did with the emitters. Nothing unusual these Chinese lights. Some might call it inconsistency, some might call it improvements. I'm just glad I got the newer one

 

[Winx]

Somehow I'm glad, that here is another RC-T5 with same kind of problem.

I emailed them and I'm going to send this back to them. I Hope I don't get similar back.

 

[wasBlinded]

What are your plans for heat dissipation?

For relatively short periods hand held at 1 amp, the heat sinking won't be much of an issue. On the bicycle, constant airflow over the light will keep temperatures lower, even with less than optimal transfer from the mounting plate to the head. Some thermal compound on the threads will be of some help too.

 

[wasBlinded]

To address the findings of Jazchau, I'll post my measurements. There may be a lot of variablility in the Vf of the LEDs that are used in these lights, so voltage vs. current draws may vary quite a bit sample to sample. Here is what I got, measuring voltage at the head with a separate DMM.

Volt Amp
6.0 .26
6.5 .51
7.0 .80
7.5 .88
7.8 .87
8.0 .86
8.5 .84
9.0 .82
9.5 .76
10.0 .75
11.0 .68
12.0 .62
14.0 .54
16.0 .48

 

[Jazchau]

wasBlinded,

Thanks for posting your numbers. Obviously the driver on my light is doing something weird below 10V. As I noted on my previous post, the current took a big drop just below 10V and then it rises sharply again near 8V. I did this several times and the result is the same. So definitely the unit I have is not behaving normally compared to yours. Well I guess I'm going to contact DX to see what they can do.

Overall, I'm pleasantly surprised at how well made this light is for the price. I may order a couple more and hopefully those won't have the issue as the one I have.

 

[Winx]

Well I guess I'm going to contact DX to see what they can do.

I bet they'll ask you to send it back for replacement. They told me to do so.

 

[wasBlinded]

Francois -

What did you have to do to remove the circuit board assembly from the main heat sink???

 

[Glowjob]

I just got mine and I beleive its a dud. with 2 18650's its 1/4 as bright as a photon keychain led. with 4 RCR123, it either wont turn on or is bright as a glow in the dark sticker after 10 minutes in the dark. I've tried 2 other sets of batteries and had the same problem. Is there somthing that I should try before I send it back, or do I have to wait for its one month journey replacement trip? Such a bummer since the other light in my order had the same problem! very dissapointing!

 

[Photon_Whisperer]

I just got mine and I beleive its a dud. with 2 18650's its 1/4 as bright as a photon keychain led. with 4 RCR123, it either wont turn on or is bright as a glow in the dark sticker after 10 minutes in the dark. I've tried 2 other sets of batteries and had the same problem. Is there somthing that I should try before I send it back, or do I have to wait for its one month journey replacement trip? Such a bummer since the other light in my order had the same problem! very dissapointing!

Are you sure you are not over tightening it? That's similar to what happens when you crush protected batteries.

 

[Xak]

When you unscrew the tail cap, does the clickie switch/battery spring bounce around like in my light? I line it up, then screw it on and it works fine. Is the reason for this to accommodate other battery combinations or do I have a loose part?

Also can GITD epoxy be put in the 3 deep grooves below the bezel or are they there for heat dissipation?

Any idea if there is a way to replace the o-ring with a GITD o-ring between the glass and the bezel?

 

[chanamasala]

Is there a way to transform this into a 3x18650 torch? Perhaps by adding another battery segment tube or two? Has anyone tried?

 

[tmax]

Is there a way to transform this into a 3x18650 torch? Perhaps by adding another battery segment tube or two? Has anyone tried?

I was thinking along the same lines today. It looks to me that if you added two more of the removable sections, you might be able to cram another 18650 in there. Now all we need is a source for the sections, short of buying two more lights.