At what Iin is the P7 most efficient?

[Upplyst]

Hello.

I am going to rebuild my 2c Nimh Mag triple ssc p4 that is driven by 3 Sandwich Shoppe Madmax plus 700 mA drivers. Drawing just under 3 amps from two 4500 mAh C batteries.

I will use the parts I have and only order a suitable heatsink, probably the one Litemania sells for the P7. I will wait for results by others, since the piedestal seems a bit high for use with the mag reflector.

Anyway, this new rebuild would consist of the following components:

Mag 2c body. P7 LED. 2 c-size Nimh. 2 or 3 madmax plus drivers in paralell, delivering 1,4 Amps or 2,1 Amps to the LED.

My question is, where is the P7 most efficient? Would I gain noticable output If I fed it with 2,1 Amps rather than 1,4 Amps?

 

[LukeA]

At what current is the P7 most efficient? About 10mA. Lower current is always more efficient (to the point where the die stops emitting light).

With higher current, yes it will be brighter, but with the increase in light output comes an even larger increase in heat output.

 

[phantom23]

25mA per die. At 10mA it's much less efficient (equally to 1A!).

 

[LEDninja]

With my MTE 5 mode SSC-P7 it is noticeable when I switch from medium (1.1A) to high (2.1A). If I do not switch I can use the medium no problem.

Why the rebuild? You probably would not notice the difference in total output but you would notice the difference in hotspot size (P7 bigger) and throw (P7 less).

Brightness comparison:
Electrolumens My Little Friend 3xSSC-P4 Fraen optic left, MTE 5 mode SSC-P7 right.

Hotspot size comparison:
L-mini 1xQ5 left, MTE 5 mode SSC-P7 right. Both with reflectors.

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From jtr1962's test data of a Q5 (I am assuming 4xQ5 dies):
http://www.candlepowerforums.com/vb/showpost.php?p=2170040&postcount=141
1.4A > .35A/die >104.97 lumens/die > 419.88 lumens.
2A > .5A/die > 141.95 lumens/die > 567.78 lumens.
567.78 lumens/419.88 lumens = 1.3522911X brighter for 1.5X battery drain.

Note these numbers are LED lumens. To get torch lumens multiply by 0.7 if you are using the stock m@g lens or 0.8 if you are using a UCL lens.

 

[Upplyst]

Thanks everyone for the input so far.


LEDninja:

I am not 100 percent sure that the p7 in a mag reflector, which I intend to implement in this project, will have less throw than my existing setup.

Three small IMS 20 mm reflectors does not throw all that well, rather a wall of light with a huge seamless hotspot. I would guesstimate at least 300 lumen. (ssc at 700 mA about 100 lumen after losses x 3)

The main reason that made me interested in the p7 was the ability to put it in one large reflector, thus gaining throw with the same or better output. The inspiration came from StefanFS projects:
http://www.candlepowerforums.com/vb/showthread.php?t=198549

 

[IMSabbel]

Also, its not strictly true that the lower you go, the better the efficiency.

For a P7, with its huge parallel dies, at the single digit range a good part of the current might as well be intrinsic.

 

[LEDninja]

I am not 100 percent sure that the p7 in a mag reflector, which I intend to implement in this project, will have less throw than my existing setup.

Three small IMS 20 mm reflectors does not throw all that well, rather a wall of light with a huge seamless hotspot. I would guesstimate at least 300 lumen. (ssc at 700 mA about 100 lumen after losses x 3)

The main reason that made me interested in the p7 was the ability to put it in one large reflector, thus gaining throw with the same or better output. The inspiration came from StefanFS projects:
http://www.candlepowerforums.com/vb/showthread.php?t=198549

You may want to look at Ernsanada's review of Elektrolumens' P7 magmod. At the bottom of the post are outdoor beamshots of the P7 (tight and wide focus) compared to an MT3 (3xP4, 20mm reflectors).
http://www.candlepowerforums.com/vb/showthread.php?t=194716

 

[Upplyst]

I had a look at the pictures and as far as I could see with my deranged old eyes the P7 had a wider spillbeam and a more intense hotspot than the triple ssc MTE III.
And this even though it looked as elektrolumens had waisted quite a bit of the bottom part of the mag reflector. If this affects throw in a negative way, I do not know. The MTE III looks quite like my own setup in every aspect. It would be nice with a comparison picture between the P7 and MTE III on an even longer range to be absolutely sure.

When I receive the necessary parts the modding will yet again commence. I will go for the parallell MadMax plus 1.4 A version initially and possibly be the first to explore the P7's ability with 2 x nimh. Time will tell

 

[jtr1962]

I'm finding that with the Cree XR-Es and P4s efficiency hits a maximum at around 50 mA, stays more or less the same until about 20 mA, and then starts dropping. Therefore, there's no good reason to go under 20 mA per die in the interests of efficiency (although there might be for battery life). For the P7 you get peak efficiency in the 80 to 200 mA range (20 to 50 mA per die). Extrapolating my figures for the Seoul P4 where you get about 110 lm/W at 50 mA, you can drive a P7 at 200 mA, get the same efficiency, and obtain about 65 lumens using only around 0.6 watts of input power. And the higher binned P7 should manage 100 lm/W efficiency at a drive current of 600 mA!