1C M@g P7 + DD = 1.2 amps at tailcap???

Hello, first I would like to thank all the fellow CPFers for all the knowledge I have gained in my short time here. :wave:

I have made several mag mods, the latest being a 2C mag shortened down to 1C cell length (by Mirage Man). As you have probably figured out by the title of this thread, I am using one Li-ion (AW) C cell to direct drive my P7 led. The P7 is a DSW0J. Even with my AW cell fresh off the charger at 4.16 volts I am only reading about 1.2 amps at the tailcap.

So my basic question is: What am I doing wrong? (perhaps the way I am measuring is incorrect?) :thinking: I have read that DDing a P7/ C li-ion normally gives above 3 amps on a fresh charge so what gives?

Here are some pics of my light, since I know how much you guys like pics.

Firstly, this is how I am measuring (is this right?):

Here are some of the light itself:

Excellent machining by Mirage Man

A glow shot

Another glow shot

Thanks again for your help!

i had a CSXOI in my L-Mini in dd, with a fully charger Li-ion i measured 1,2A at the tailcap

Current to the P7 will be MUCH higher with the meter out of circuit

lctorana said:

Current to the P7 will be MUCH higher with the meter out of circuit

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MUCH higher...how so?
All of the digital meters I've used in the last 20 years have never introduced more than one tenth of an ohm of resistance when used on the internally shunted 10 or 20 amp setting and this figure includes the resistance of the test lead wire.
How much resistance is there from lead tip to lead tip on your meter when the leads are plugged into the 10/20A plug and ground?

If there is a difference on the order of 1 Amp or more between with and without the meter, then the OP should very easily be able to notice the difference. Since it wasn't mentioned, it seems safe to assume that output was relatively consistent. You *did* check, didn't you?

AFAIK the DSW0J has higher VF than most of the C bin P7's that's been out. Maybe that is affecting the current output on the cell? Have you tested your meter and setting on another high power light lately, justs to confirm things?

mudman cj said:

If there is a difference on the order of 1 Amp or more between with and without the meter, then the OP should very easily be able to notice the difference. Since it wasn't mentioned, it seems safe to assume that output was relatively consistent. You *did* check, didn't you?

Click to expand...

There was a difference. I don't know if it looks like a >1 amp difference though. Here is what the two looked like:

Light running normal on left, light with MM on the right

lowatts said:

AFAIK the DSW0J has higher VF than most of the C bin P7's that's been out. Maybe that is affecting the current output on the cell? Have you tested your meter and setting on another high power light lately, justs to confirm things?

Click to expand...

Yes, I tested a Mag11 and a Mag85 and compared it to Lux's destructive incan test data for those bulbs. The numbers were pretty much where they should have been, so I don't think it is the multi-meter.

FWIW I have a 1D MAG P7 C-bin DD but i opted for using a .15 omh 5 watt resistor so that I wouldn't overdrive my P7 C-bin LED. The amperage using the D size li-ion is 2.3Amps. Same host substituting with one AW C size li-ion and the amperage drops to 1.8Amps. I like the D size li-ion solution better but i do agree that the C size is smaller but dimmer.