3D MAG with P7

If I run a P7 on a 3D mag, what would happen if I tried to direct drive it with 3 regular d cells? Would I burn it up? Would any kind of resistor work for this?

If I'd be better running a driver of some kind, what do you recommend?

Thanks in advance!

You should be able to direct-drive a P7 with three alkaline D-cells. Output may only be about half of what you'd get if you were running NiMH cells due to the higher internal resistance of alkaline cells.

So if I ran NiMH cells, would it be too much to direct drive the led?

What do you think of these?
http://thomasdistributing.com/shop/...html?SP_id=&osCsid=odckufjhd5qe4d1vgh3b06rjq3

Depends on which bin of the P7 you get, if it's a J-bin, it would probably be fine, with an I-bin you might be on the edge. I have these batteries and they will put out a 4 Amp load fresh easily. I have 2-1400ma drivers, along with a 1000ma multi-mode to give me a total of 3.8A (actually a tad bit higher at around 3.9A) to the LED.

You figure 1.4v fresh would give you a 4.2v total. It would probably be safer to just do 2-1400ma AMC7135 drivers, but it would probably work for a little while anyway. I know I'm direct driving another light off a 18650 Li-Ion cell to an I-bin P7 led, which would be a very similar voltage, but only a 3A load.

wildstar87 said:

Depends on which bin of the P7 you get, if it's a J-bin, it would probably be fine, with an I-bin you might be on the edge. I have these batteries and they will put out a 4 Amp load fresh easily. I have 2-1400ma drivers, along with a 1000ma multi-mode to give me a total of 3.8A (actually a tad bit higher at around 3.9A) to the LED.

You figure 1.4v fresh would give you a 4.2v total. It would probably be safer to just do 2-1400ma AMC7135 drivers, but it would probably work for a little while anyway. I know I'm direct driving another light off a 18650 Li-Ion cell to an I-bin P7 led, which would be a very similar voltage, but only a 3A load.

Click to expand...

From my experience, even I vf (3.25V-3.50V) P7s work fine in a direct drive 3D Mag. NiMH batteries eventually settle into their 1.2V spec after running for a bit. I was told by one of my flashlight mod buddies that he was able to run a P7 direct drive in a 4D Mag for around an hour before the switch melted. LEDs can usually handle higher voltage out of spec...you're more likely to fry an LED from too much current than too much voltage, generally speaking.

I build a lot of 3D direct drive P7 and you will do fine with the set up. The batteries you have specified will work great and that is a great price on that brand battery. Alkalines will work but won't give you near the performance that the batteries you have picked will.

I use 10,000mah tenergy's and they will give you a run time of close to four hours.

If you want dimming you can even hook up a d2flex board although it is a little more complex because of the switch mod you need to do.

One of the most important items is a good contact between the led and the heatsink after that you will be good to go with those batteries.

As Ace001a said the voltage will be fine. I actually run P7 with two cr123 in different host which is 6 volts and they do fine and I have used C bins through the latest j bins and not had any trouble with your setup.

Dave

I hope I'm not beating a dead horse here...

I got to looking, and I think what I'm going to use will actually be the c-bin from dx.
http://www.dealextreme.com/details.dx/sku.12721

Does that change anything?

Would this one be better?

http://www.dealextreme.com/details.dx/sku.11809
should I put it on this?
http://www.dealextreme.com/details.dx/sku.12193

IMHO the c bin would be better than the b bin that is shown there. As the bin goes up so does the lumens. I have direct driven C bins with the config that you are going to use no problem.

You will not need the round board with most of the heat sinks used here on the forum. Most of the sinks have a pedestal that you will AA the bare emitter to.

Dave

UPDATE! Thanks for all the help!

I just ordered a p7 dsxpj, heat sink, and metal orange peel reflector from brightlumens.

My first thought, as above, is to direct drive this using 3 d cell batteries. I just need to figure out which batteries. I don't have any d sized chargers yet, so I'm starting from scratch. I don't want to spend a fortune either.

I was looking at the ones posted above, the accupowers.
http://thomasdistributing.com/shop/...html?SP_id=&osCsid=odckufjhd5qe4d1vgh3b06rjq3

What kind of charger should I use with those? Is there a different battery that will give me good power and runtime that's cheaper?

I found a good deal on some 10,000mah tenergy's and got them.

Should I wire in a resistor, or will I be ok?