P7 Battery Advice

[TakingVacation]

I've got one of those on order, but I think the problem is going to be that it won't get you to 2.8A on a 3D Nimh cells. I'm having trouble getting 3D's to get me to the needed Vf on the DSWOJ's that I got from LiteMania. They have a great color to them, but may be at the top end of the BIN at 3.75 volts. So when the batteries come of the charger they are at 1.4 x 3 = 4.2 and when you hit the switch on the mag (cut and direct wired to accomodate the heat sink that also came from LiteMania) the voltage drops about 10% = ~3.75. Shortly, the voltage on the batteries drop closer to 1.25 volts = 3.75 volts leaving the voltage at the emitter at 3.36 or so and the DMM showing about 1632ma so the output really falls off with the Direct Drive (DD) Nimh. I'm running the same setup on a 2D with 3C's in a 1.25" PVC sleeve on another Mag with the same issue.

I think I have a few choices, and maybe you as well:
Run 4C's in a 3D body - cut the tailswitch down, and either add a 1ohm resistor or drop the voltage with some type of circuit board down to 2.8 (either KD or DX).
-Or-
Go out and spend the money on a boost driver
-Or-
Spend the money on a I Bin with lower forward voltage where the P7 will draw more amps at a lower voltage
-Or-
Get about and equal result on a DD Li-ion and having to deal with either cutting down the maglite (which would be nice) or putting in a dummy cell or going with 2 Li-ions and using a circuit to drop the voltage
-Or-
Live with the lower voltage and amps and lower output but gain longer run times and have about 60% of the max brightness

In the end, it comes down to how many dollars to spend to get the J Bin voltage optimized on a 3D setup.

By the way, both my 3D and 3C are almost exactly the same with voltage and amp measurements. I do think the 3C 5000 Mah Tenergies actually seem to hold their initial voltage longer than the Titanium 12000 Mah D-cells

I'm happy with the output now, as they are twice as bright as my 240 lumen maxed out R2 LED light and way brighter than anything off the shelf, but like most that are now addicted to this stuff - I want more light and things to run near the max of their potential.

This is my take on things, but would really like to get some direction on another alternative that might help squeeze out a few more Volts/amps from a 3D or 3C setup that are DD on the J bins P7's....

 

[TakingVacation]

More measurements last night. I'm guessing the LED on my 3D Mag is at the max of the Bin range. Does this seem right: Fresh 3C's off the charger at 4.14 total no load volts, 3.75 across the LED, measured 2.8amps. A few minutes later, with the light back to room temp: 3.98 volts, 3.53 volts across the LED, and 2.6amps.

The conclusion is that 3C's is barely enought to drive the DSWOJ that has a 3.75V preference at 2.8 amps. Right??

I have the switch cut down, tailspring is cut down to make room for the longer D NiMh's and jumped with copper wire, 22 guage copper wire from switch to LED cathode and anode leads.

I have a question? If I switced to an I Bin, like a CSWOI or CSXOI would I get more output - would runtimes vary. At this point, at the NiMH nominal 3.6v (total on 3D/3C's), it's going to only be pulling about 1.6 amps (3.36 across the LED). So to use about 80% of the battery = ~ 6 hours runtime.

 

[DocD]

Hi,
If your going to use c bin or d bin P7 can i add that the battery makes a big diffrence to the way things happen to your P7
as we all know I-bin=3.25,3.5 volts and j-bins 3.5,3.75 volts
i think i read in a thread that D-bin are not as bright as C-bin on DD but i can't remember the reason why?
i feel for DD it's better to use j bin and i-bin for regulated some but CPF'ers have used I-bin on DD so maybe i have been unlucky as all have turned blue and died but i think also you have to factor in battery choice to as well VGQ battery more start power for the mill second it take the led to power up before any internal resistance builds up and the heat at the led and the control away in too the heat sink.
just to add i don't think it's a good idea to try 4 cells to power a P7 it would just burn up for sure
just some of my thought's cheers DocD

 

[uluapoundr]

Dont mean to hijack this thread but I have a question that relates. I have a 3 d mag with a P7 running direct drive. At first i ran on 3 d alkalines and everything looked good. Swithed to 3D Tenergy NiMh's and it looks good for about 20 seconds then LED starts turning blue. I'm new to all this so bear with me here, I checked resistance from negative side of batteries to inside tube and read around 2.8a at first, then it rose to around 4a when LED turns blue.What's going on?

Now it gets worse, just put alkys back in and it still turns blue. Did I just ruin my P7?

I've burned two P7 "I" bin emitters after it turned blue. Off the charger and rested for a few days my tenergy cells are 1.32x3=3.96v. Measured amps at the spring 3.8 and light starts turning blue. I'm assuming this is way too much amperage. Put in slightly used Tenergy cells at 1.23v each and got 2.7-2.8A and light stays white. Using alkaline and much lower readings...can't remember the V but A is below 2.8 and never turns blue, but not as white with the NiMh cells.

 

[nailbender]

Hi Uluapoundr

Unless you have some very low Cbins there is something else going on. Jimmyswan and I talked back and forth for several nights via PM and I told him that by using 3 NIMH it is almost impossible to burn a P7 geeze I run two cr123 in my one D direct drive Dbin (6 volts) not RCR123 and still can't fry the thing.
I asked Jimmyswan to make sure the LED was AA down properly, after he got home from work he found out that the imitter was not AA down properly and once he had reglued the LED down he wrote me that he now has a very satisfying P7 light that now has no problems running the 3 tenergy's.
You measured at the spring I bet it is lower at the led since the switch and wires even if kept extremely short using teflon wire as I do when building the resistance is going to cut that figure down.
I built my P7 yesterday using Derwitchel driver & D2Flex dimmer and I measured 2.8 amp.at the LED and I ran it for 30 minutes last night no problem.
After reading this I ran a run test on 3 Tenergy Mah since I build quite a few of these since with no dimming I can keep the cost down and after 3 hours I could still hit a house 2 hundred Yards away that I use for my tests with a strong light but not like new batteries. I would imaging I still had close to an hour I could have used at reduced capabilities. I have some law enforcement that use alkalines in them and they are 1.5 although they sag so fast there is little difference.
I would check everything over again since these P7's are quite bullet proof yours may still be good but I have found out they do not run worth a durn without proper heatsinking.

Dave