Direct Drive P7 M@g Experience

[Alan B]

I'm putting together a few Direct Drive P7 D M@gs and I thought there might be interest collecting my and other's results into one thread. With DD there is always some question of what current one is actually going to get. I'm using a Taskled D2Flex, and I measured the PWM and the current as well.

Here are the components in this unit:

1D M@g from wgiles
3AA holder from mdocod with eneloops, or
1D unprotected Li-Ion from KD
Heatsink from Britelumens
DXSOJ P7 from photonfanatic
Modified stock switch, 20 ga wire
No extra resistance
Stock tailcap and spring (which were out of circuit when measured)

D2Flex PWM measured with scope:
1 4us 0.016A
2 50us 0.200A
3 130us 0.520A
4 280us 1.12A
5 Full On 2.0A

period was 511uS, times shown above were on-times

The above current is with the KD D cell at initial charge (as delivered). Three Eneloops well rested produced 1.8A.

Current measured with Fluke 189 DC true RMS meter. Above values are calculated from PWM, measured values were close except for setting #1 which likely exceeds the crest factor and capability of the meter to accurately measure it. Other measured values were slightly lower than above calculated results except at full on.

So the bottom line here is 1.8 to 2.0 amps max. The current did drift up slightly as the LED warmed.

So I'm curious what other setups folks tried and measured. What current did folks get with 3-4AA, 3C, 3D 18650, etc cells, "I" Vf bin LEDs, etc. Please post your summarized results and some details here. I've searched for this type of info but didn't find much. This info can be helpful to others. Also links to any other data would be good here as well.

Thanks for your info,

 

[sami_voodoo]

I've tried a Trustfire 18650 Li-ion on a 3D Direct Drive (on D-alkaline) P7 Mag. The LED is a DSWOI P7 I got from Photonfanatic.

I connected the battery directly to the LED. Positive terminal on one leg of the LED and a connection from the Negative terminal via an Ammeter. I got 3.4 amps for a second or so. On brand new Duracell D-cell alkalines (3x), I get 2.2 amps.

I hope this helps! Cheers,
Sami

 

[Alan B]

I've tried a Trustfire 18650 Li-ion on a 3D Direct Drive (on D-alkaline) P7 Mag. The LED is a DSWOI P7 I got from Photonfanatic.

I connected the battery directly to the LED. Positive terminal on one leg of the LED and a connection from the Negative terminal via an Ammeter. I got 3.4 amps for a second or so. On brand new Duracell D-cell alkalines (3x), I get 2.2 amps.

I hope this helps! Cheers,
Sami

Thanks for the data. Good info. Wow on the current!

 

[sami_voodoo]

The Li-ion was at about 4 volts when I did the test, so a fully charged one could be even higher in current (or maybe not - with the voltage sag)

IIRC, the D2Flex is rated for a maximum of 3.4 amps. http://taskled.com/compare.html I don't think I'd be able to use that with a fully charged single cell Li-ion with an I-bin P7. Come to think of it, is it possible at all to drive an I-bin P7 from one Li-ion?

In any case, I'll wait to see what experiences others have had with P7s.

 

[Alan B]

If the Vf is 0.25V different then it would take about 0.1 ohm to drop the voltage and make an I bin behave like a J bin at 2.5A. So to hit 2.8A would take even a bit less (hard to predict exactly due to LED Vf variation).

 

[sami_voodoo]

So power lost in the resistor would be I²R or 2.8²x0.1=0.78 Watt.

Or, in other words, the system is (2.8*3.25)/(0.78+(2.8*3.25)) = 92.1% efficient. Assuming a Vf = 3.25 and If = 2.8 A.

Not bad at all IMHO Now I know what I'll be doing as a future project.

Thing is, until now I was dismissing the resistor mod as a band-aid measure.

Cheers!
Sami

 

[Alan B]

Precisely. Adding a little impedance on direct drive can still produce a very efficient system. Regulators are nice, but not 92% efficient very often.

Using the "J" bin P7 with direct drive does make for a very efficient system, both in terms of electrical loss, and in terms of the LED efficiency going up a bit with lower current. However the Jbin does not quite reach full output with the batteries I have tried thus far. However 2.0 amps is not a bad place to operate, it makes the heatsink's job a lot easier and puts out a lot of lumens...

 

[sami_voodoo]

Alan

i think you've already gone through jtr1962's thread. i've posted it here anyway, since I've used it as reference to determine light outputs of various LEDs. Here's a post showing the output vs. current curve for a C-bin P7:

https://www.candlepowerforums.com/posts/2668288&postcount=229

At 2.0 amps, you're making just under 80% of your rated lumen output at 2.8 amps. ~700 perhaps for a D-bin?

I've tried the DD approach at 2 amps (start of test), and on a 3D mag with the H22A sink, it can run for hours on end (I tested until 4 hours when the current was down to 0.5 amp) without heat problems. In any case, I suppose it's the first half hour or so where the LED gets the full blast from the alkaline D-cells.

 

[Northern Lights]

I have used the same P7 bins. The Vf on the D bin , J bin, 800-900 lumens at 3.7 volts is 3.7 volts not 3.6 although running the J bin on the 3.6V batteries it is brighter than the C bin which has the Vf of 3.6 Volts.
I used both D2flex and D2DIM mode drivers. I measured 3.0-3.1 amps current on one configuration but I do not know if that happens all the time. I did use the D lithium batteries in some test but the emolie is better for this.

Emolie 26700 and 18650s will deliver 3.7-3.9 V bat nominal and conversely you will get the performance then. They are brighter than either C or D bin on lithium Ion 3.6 batteries. If you can see the difference surely it will meaure differently too.

When deciding to go direct drive I choose the emolie because it has a nearly flat discharge curve and looks like a regulated discharge and it has the voltage to get thecorrect and maximum current on the LED. The conundrum is that the P7 is so good that even when run at lower currents it crushes the competition and is acceptablea and impressive for light output. Put it on the correct amount of current and it is very bright!

To say simply the P7 listed in post #1 is designed to run at a higher voltage than the batteries listed can provide. When given the correct voltage you should see a very noticable improvement. I did it and it convinced me.

 

[Alan B]

Alan

i think you've already gone through jtr1962's thread. i've posted it here anyway, since I've used it as reference to determine light outputs of various LEDs. Here's a post showing the output vs. current curve for a C-bin P7:

https://www.candlepowerforums.com/posts/2668288&postcount=229

At 2.0 amps, you're making just under 80% of your rated lumen output at 2.8 amps. ~700 perhaps for a D-bin?

I've tried the DD approach at 2 amps (start of test), and on a 3D mag with the H22A sink, it can run for hours on end (I tested until 4 hours when the current was down to 0.5 amp) without heat problems. In any case, I suppose it's the first half hour or so where the LED gets the full blast from the alkaline D-cells.

Here is the thread mentioned above:

https://www.candlepowerforums.com/threads/89607

 

[Alan B]

I have used the same P7 bins. The Vf on the D bin , J bin, 800-900 lumens at 3.7 volts is 3.7 volts not 3.6 although running the J bin on the 3.6V batteries it is brighter than the C bin which has the Vf of 3.6 Volts.
I used both D2flex and D2DIM mode drivers. I measured 3.0-3.1 amps current on one configuration but I do not know if that happens all the time. I did use the D lithium batteries in some test but the emolie is better for this.

Emolie 26700 and 18650s will deliver 3.7-3.9 V bat nominal and conversely you will get the performance then. They are brighter than either C or D bin on lithium Ion 3.6 batteries. If you can see the difference surely it will meaure differently too.

When deciding to go direct drive I choose the emolie because it has a nearly flat discharge curve and looks like a regulated discharge and it has the voltage to get thecorrect and maximum current on the LED. The conundrum is that the P7 is so good that even when run at lower currents it crushes the competition and is acceptablea and impressive for light output. Put it on the correct amount of current and it is very bright!

To say simply the P7 listed in post #1 is designed to run at a higher voltage than the batteries listed can provide. When given the correct voltage you should see a very noticable improvement. I did it and it convinced me.

Thanks for the info. I haven't tried the Emolie batteries yet. Sounds like they work well.

I have compared the light output on the P7 from 2.0A to 2.8A on the power supply, and the difference is hard to see. There is already a lot of light output at 2A. It is fun to run the current to the max, but even 2A is an excellent amount of light, and the batteries last longer. And it is easy to build and saves $ in the build cost.

 

[Northern Lights]

Thanks for the info. I haven't tried the Emolie batteries yet. Sounds like they work well.

I have compared the light output on the P7 from 2.0A to 2.8A on the power supply, and the difference is hard to see. There is already a lot of light output at 2A. It is fun to run the current to the max, but even 2A is an excellent amount of light, and the batteries last longer. And it is easy to build and saves $ in the build cost.

Those D cells are still and excellent choice. Like we both said, P7 works well with a lot of light on those..
Check out FS, I have too many of the Ds personally and am letting some go.

FS-D lithium, immediate delivery, LED and INCAN mods now

 

[Alan B]

Those D cells are still and excellent choice. Like we both said, P7 works well with a lot of light on those..
Check out FS, I have too many of the Ds personally and am letting some go.

FS-D lithium, immediate delivery, LED and INCAN mods now

Agreed, and good luck with your sale. I may have to sell a few some time as well, these fun projects are piling up a bit. I'm also planning to build a triple P7 at some point. I picked up one of Mac's and that has slowed my project but I'll get back to it later.

 

[Alan B]

We put together another DD P7 yesterday in a 2D with 3C Alkalines. The current measured up to about 2.3 amps with new Duracells. This with a "J" bin.

 

[sami_voodoo]

Alan

Any mods to the switch or the tail spring?

 

[Alan B]

Alan

Any mods to the switch or the tail spring?

3C cells in a 2D requires a tailcap/spring mod. The owner of the light put in a different spring from another flashlight. There is very little room so the thin spring he used bends backwards into the tailcap. It is probably going to be improved further. The clearance from the battery stack to the tailcap is probably about 1/8". I did not measure it.

 

[sami_voodoo]

Alan

I'm just wondering how I was getting 2.2 amps on an I-bin with 3 D-size Duracell alkalines and not higher . Logically, a J-bin should draw less current, isn't it? Did you do any switch mods to reduce resistance?

 

[Alan B]

That sounds too low. Were the cells in good shape?

Our setup is using a D2Flex, so the switch is not in the current path. Measurements taken at the tailcap, so the tailcap and spring are not in the circuit. Meter probes are included, and those do vary.

 

[sami_voodoo]

The cells that I have seem to be fresh. They're made in Belgium. Unfortunately, I've sent the 3D P7 off to my younger brother as a gift. I'll try to make another one soon, and then I'll run a test with different cells. I might do one like you. A 2D Mag with 3 C-cells. Then I'll share my experience.

 

[M@elstrom]

I've tried the DD approach at 2 amps (start of test), and on a 3D mag with the H22A sink, it can run for hours on end (I tested until 4 hours when the current was down to 0.5 amp) without heat problems.

This is the approach I also took using a DSWOI P7, the service life of the Alkaline D cell is quite good though output appears to drop below 150Lm when the cells reach about 1.0~1.15v (unloaded) :thumbsup: