Beginner question about P7 current draw

I have built up two P7 lights, both DD:

M*g 3D, CSXOI, 3 x 10,000mAH NiMH
M*g 1D, DSWOJ, 1 x AW C-LiIon - 3300mAH

I think the P7 is rated max output at 2.8A. I measure my lights at the tailcap and only get:

M*g 3D = 2.45A
M*g 1D = 2.06A

So it would appear I'm not getting max output. Should I be doing something like resistance mods to get more current through the LED's?

Obviously, I'm fairly new at this and appreciate the advise. BTW, the LED's are quality components from PhotonFanatic.

Many thanks!

I am in your same boat, I would like to get as much as possible out of my P7's as well. I am building the 3a driver/pwm solution that stephan uses for in his. But as far as batteries I think what you have is top notch. Use good wire(got mine from mudman cj per stephan's suggestion) and maybe add the braided copper wire to the tail cap spring to lesson the resistance?

So what do you see from your lights as far as a difference in brightness from the two types of batteries? Just curious, I am thinking AW C lion as well. I really would like to use an FM 3x17670 holder and a driver that would regulate correctly, I would like mine to run a while on max levels.

I am new to this as well so I have a lot to figure out.

BTW I have the same emitters from the same place.

Drew

Resistance mods like this could help. That thread talks about an old dirty switch measured as having "18 to 100 ohms" and applying progold dropping it to "6 or 8 miliohms." The rest of the mods only got it down to 1.43 milliohms measured so there are diminishing returns for the work. Try cleaning all your contacts and see what it gets you.

Although I am not DD'ing, I did use 20 gauge wiring for my install. Forget about the OEM metal tabs and such. They're bottlenecks. I'm getting 2.8A from the tailcap.

cd-card-biz said:

I have built up two P7 lights, both DD...

...I measure my lights at the tailcap and only get:

M*g 3D = 2.45A
M*g 1D = 2.06A...

Click to expand...

But you will get WAY more current draw when the ammeter is not in circuit. With direct drive, the LED is very sensitive to input voltage, and the burden voltage of your meter (anything from 0.1 to 0.4 volts) will reduce the voltage the LED sees to the point where the current drops sharply.

lctorana said:

But you will get WAY more current draw when the ammeter is not in circuit. With direct drive, the LED is very sensitive to input voltage, and the burden voltage of your meter (anything from 0.1 to 0.4 volts) will reduce the voltage the LED sees to the point where the current drops sharply.

Click to expand...

This may explain a lot. I failed to realize that the meter itself could change the measurement. Then is it not really possible to get a good measurement of current drawn using DD?

I will still do the resistance fixes that I remember from my hotwire builds and see if that changes anything.

I'm thinking of just getting one of the KD single mode P7 drivers here. However, I dread falling into another epic 3-month waiting-for-delivery saga.

I have that driver and I'm in socal also. It took only 2 weeks from the day I ordered it to the day I received it in my hands.

GSteg said:

I have that driver and I'm in socal also. It took only 2 weeks from the day I ordered it to the day I received it in my hands.

Click to expand...

Thanks GSteg, this is encouraging! I've had mixed results in the past. I may try one of the Super 3-mode drivers as well as the single mode.

Hey, in your previous post you said "forget about the OEM metal tabs....". Do you mean the internal M*g switch tabs?

Thanks!

Adding that driver will not increase the current to the LED it will only reduce the current if it exceeds 2.8 amps.
But yeah reducing the resistance in the circuit should help heaps.

I built a DD single 18650 Li Ion cell light with a P7 and got over 3 amps.
I tried another P7 that came in the same order and it was less the 2.4 amps.
Vf was 3.1v and 3.7v.

Your CXOI should have a lower Vf so that may be a better choice for the Li Ion torch.

Where did you get the D bin P7?

Packhorse said:

Where did you get the D bin P7?

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From PhotoFanatic here. He is a good source for LED's, reflectors, adhesives and ships quickly.

I plan to use the drivers for 2 x LiIon C-cell and 9 x AA (in FM 3D cell holder).

Going to try the resistance fixes and see how they look.

-Thanks

cd-card-biz said:

Thanks GSteg, this is encouraging! I've had mixed results in the past. I may try one of the Super 3-mode drivers as well as the single mode.

Hey, in your previous post you said "forget about the OEM metal tabs....". Do you mean the internal M*g switch tabs?

Thanks!

Click to expand...

yup! I added wires from the internal switch to the LED driver. The tabs are still there, but most of the current is traveling through the wires I added.