Crelant V4A mini-review

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Leif
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Crelant V4A mini-review

As I’m sure you all know this is a 4 AA light with an XPL-Hi LED, at a very reasonable price, claiming constant current circuitry, two output modes, max at 1000 lumens, and some hidden joke modes.

Mine is nicely made, not quite flawless, but pretty much on a par with Fenix et al externally at least. The integral battery carrier is nice. The switch design is nice, only two modes (plus hidden joke modes), and each is adjustable by ramping, just hold the switch down, very nice.

I did some measurements yesterday and it got very hot. By 1 hour is was dim, I forgot to measure after 35 minutes. After 35 minuttes it was down to 550 units from 780 at the start. Today I repeated the tests, and the regulation was worse (not sure what has happened, maybe room temperature changes?):

5:10 = 939
5:15 = 745
5:20 = 695
5:25 = 6:50
5:30 = 605
5:35 = 562
5:40 = 623
5:45 = 487
5:50 = 43*
5:55 = 400
6:00 = 366
6:05 = 330
6:10 = 300
6:15 = 268
I then got bored ….

The units are arbitrary since I cannot accurately measure output, only brightness in lux.

So it looks as if the previous run on high has burnt something out in the circuitry or the LED. My feelings are that this light is best avoided. It has poor regulation. I noticed from other reviews that Crelant lights seem to have poor regulation. What a shame. It seems also to be inefficient compared to my other lights, but then again it could be that running on very high (near 1000 lumens apparently) at the start takes its toll, since an LED drains battereries disproportionately when run at very high outputs.

As for mine, the poor regulation means it will be relegated to sitting in the car as an emergency light. Even then I’m not convinced the circuit efficiency is good, so perhaps it should not go in the car, where I might need light for a long while e.g. if walking at night after a breakdown.

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Edited by: sb56637 on 09/02/2017 - 11:48
Leif
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Here is the output in a graph form:

Dreadful regulation, and not consistent with the description on the sales page. Sad

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Leif
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Incidentally, to repeat what I said in post 1, these are arbitrary unit and NOT lumens.

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djozz
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Thanks for the output test. From what the few pictures show that people have posted, the driver seems a simple fet-driver with lower settings pwm-ed by a MCU. This curve is about what to expect from that, and in my opinion there is nothing wrong with it, the light is very useful with such a steady output slope. It is just not great, and certainly not as advertised.

WalkIntoTheLight
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Your output graph looks very similar to what I’ve seen with my light.

Stereodude
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djozz wrote:
This curve is about what to expect from that…

I’ve got to disagree with you here. The output slope should basically mirror the voltage discharge curve of a NiMH battery, which is not a constant linear decline.
WalkIntoTheLight
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Stereodude wrote:
djozz wrote:
This curve is about what to expect from that…
I’ve got to disagree with you here. The output slope should basically mirror the voltage discharge curve of a NiMH battery, which is not a constant linear decline.

That assumes that the LED produces light directly proportional to the voltage supplied to it. When I look at Cree’s spec sheets, that is not the case. Below about 2.6v, the LED isn’t producing much light at all. Then it’s close to a linear increase in lumens from 2.6v to 3.4v. Then it starts to taper off (or just blow the LED).

I estimate, based on the initial output of this light (close to 1000 lumens), that the LED is getting a forward voltage of about 3.3v. If 4xAA Eneloops are giving about 5v under load at this point, then the resistor that is dropping the voltage probably drops it by about a third.

I’d expect to see an exaggerated output curve of the light, that corresponds to the discharge curve of the batteries. That is, a steeper drop than what the battery voltage is. Because the LED goes down to zero when the forward voltage drops below 2.6v, which is about 3.9v from the battery (about 0.97v per cell).

Stereodude
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WalkIntoTheLight wrote:
That assumes that the LED produces light directly proportional to the voltage supplied to it…
No, it doesn’t. There has to be a current limiting resistor or some current limiting circuitry in the V4A. They are not just wiring 4 NiMH cells in series across the LED or it would fry something (LED, PCB traces, FET, wiring, etc) when you use cells with very low internal resistance.

So, as the batteries discharge their voltage drops (but the have a fairly large & flat plateau after the initial voltage drop). The voltage drop causes the current through the circuit to drop. This current drop means the voltage drop across the current limiting resistor (which sets Vf) decreases too. Meaning the LED gets a proportionately a greater share of the voltage coming from the batteries as they discharge because the resistor is taking a smaller and smaller share. This effect coupled with the voltage discharge curves of NiMH under load is how they can give psuedo regulation in a light with just a current limiting resistor even though the LED does not respond linearly to Vf. Vf is more stable than the voltage coming off the batteries.

Theodore41
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I received it today,put in 4 AA alcalines, and measured it with my luxmeter.The result is 32693CD.Some other measure done?

Stereodude
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Theodore41 wrote:
I received it today,put in 4 AA alcalines, and measured it with my luxmeter.The result is 32693CD.Some other measure done?
At what distance?
Theodore41
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Stereodude wrote:
Theodore41 wrote:
I received it today,put in 4 AA alcalines, and measured it with my luxmeter.The result is 32693CD.Some other measure done?
At what distance?

At 4.8m.
Theodore41
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I ordered a new luxmeter,and I measured again with this one.I had the same results,ie about 34000cd.As the manufacturer,writes in the user manual,the intensity should be 68000cd,so I see 50% less.If you find the same,we could complain to the seller.If we are many,it would be a response,otherwise,with me only complaining,who cares…