p7 direct drive, amps?

LEDBE
f22shift

f22shift

Flashlight Enthusiast
Joined
Jun 4, 2007
Messages
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Location
Singapore, NY,SH,BJ
i'm using a direct drive to the p7 in a mag3d using 2aa->1d battery
http://www.dealextreme.com/details.dx/sku.3228
carries for a total of 6aa.
i'm only getting 2.2a at the start 4.16v, 0 min
1.71a at 3.89v, 30 min
1.45a at 3.78v, 60 min

i'm using a dmm at the tail to measure. my question is how accurate is this measurement?

also for a driver
am i better off with
http://www.kaidomain.com/WEBUI/ProductDetail.aspx?TranID=4338
or
http://www.dealextreme.com/details.dx/sku.1886
which is the same thing as the kd driver i guess but use in parallel

i'm willing to wait for something better.
 
Last edited:
Dang. I was hoping you were using alks, in which case I'd just say, "well there's your problem." :) Oh well.

Are you measuring that voltage OC, no load? If you can manage it, measure the voltage while the light is on. If you want to measure the voltage at the tailcap, you'll need to bridge the -ve of the batt to the body tube somehow. The preferred way is to put the DMM probes right on the emitter leads, then look far away from the emitter and turn the light on. :cool:

Are the cells hot off the charger (it sounds like they are)? If they've rested for several hours or a few days, they may be self-discharging in the meantime (D2650s sometimes have that issue).

If everything's hunky-dory, with no crazy resistance anywhere, no damaged cells, etc., then it might be a P7 with an unusually high Vf. That would be a rare conclusion, however.
 
TigerhawkT3 said:
Dang. I was hoping you were using alks, in which case I'd just say, "well there's your problem." :) Oh well.

Are you measuring that voltage OC, no load? If you can manage it, measure the voltage while the light is on. If you want to measure the voltage at the tailcap, you'll need to bridge the -ve of the batt to the body tube somehow. The preferred way is to put the DMM probes right on the emitter leads, then look far away from the emitter and turn the light on. :cool:

Are the cells hot off the charger (it sounds like they are)? If they've rested for several hours or a few days, they may be self-discharging in the meantime (D2650s sometimes have that issue).

If everything's hunky-dory, with no crazy resistance anywhere, no damaged cells, etc., then it might be a P7 with an unusually high Vf. That would be a rare conclusion, however.
Click to expand...


thanks for the responses guys.

i just took the batteries out to measure the voltage rather than the voltage on a load.
the batteries were 6hrs off of the charger. i'd rather not run it hot because i wanted a realistic runtime.
i'm going to give it a go with 6 sanyo 2700 tonight. see if there is a difference.
at 2hrs it's pulling around 210ma at the tailcap with the duracells. looks to be about 75 lumens. i guess it could keep going since it's not regulated.

the p7 is from photonfanatic so the vf is low.
(W724C0-CSW0I), color bin SW0 (6060K), Vf: I = 3.25 - 3.50V. 740 - 900 lumen output at 2.8A.

i'll also try just taping 3 aa in a row to see if the amps are the same during the battery life. (eliminate carrier resistance)

would the KD driver work for me? i noticed they mentioned using 4aa but i have a 3aa setup.

EDIT: just tested taping 3aa together, pulls the same as with the carrier. it doesn't get more direct than that.

i'll test the sanyos later.
 
Last edited:
Shouldn't the voltage on 6AA be more that 4.16V? On a fresh charge shouldn't the voltage be at least 6V and close to 7V. 1.2V per AA would yield 7.2V for 6 cells. Should the voltage drop immediately under 5V with a load?

Running a P7 on a single emoli cell, Mac got 3.2A current on his build. I am building 2 P7's with a single emoli DD. Will running DD over the recommended 2.8A shorten the life of the LED?

Pardon me if these are stupid questions, I am just new to this and don't understand all I know about it yet.

Thanks
 
rolltide said:
Shouldn't the voltage on 6AA be more that 4.16V? On a fresh charge shouldn't the voltage be at least 6V and close to 7V. 1.2V per AA would yield 7.2V for 6 cells. Should the voltage drop immediately under 5V with a load?

Running a P7 on a single emoli cell, Mac got 3.2A current on his build. I am building 2 P7's with a single emoli DD. Will running DD over the recommended 2.8A shorten the life of the LED?

Pardon me if these are stupid questions, I am just new to this and don't understand all I know about it yet.

Thanks
Click to expand...

parallel
2aa->1d
so 1.4v(2500x2=5000mah capacity)x3 carriers= 4.2v 5ah initially
 
Ah, 2 in PARALLEL, I thought all were in series. My mistake.

I would have thought the NiMH's would produce more current also.

Let us know how it comes out with the sanyos.
 
rolltide said:
Ah, 2 in PARALLEL, I thought all were in series. My mistake.

I would have thought the NiMH's would produce more current also.

Let us know how it comes out with the sanyos.
Click to expand...

Well NiMHs have a relatively flat discharge curve compared to Alkalines which really sag once you put them in anything other than in low current draws. With that said, those cheap 2AA-to-1D parallel adapters sold at DX don't have enough good metal on them coupled with the flimsy design makes me believe that they introduce alot of resistance.
 
duracell 26506hrs off charger
sanyo 2700 3hrs off charger
the duracells are older and more used. could be that.
or could be the time off the charger
i'm such an idiot. i should've waited the 6hrs. i did a reading of the sanyo at 1hr off the charger, it was 4.2v at 2.90a.

worthless data i suppose...:mecry:


minutes, volts , amp
0 , 4.16 4.20, 2.21 2.35
30 , 3.89 3.91, 1.71 2.26
60 , 3.78 3.80, 1.45 1.93
90 , 3.58 3.60, 0.75 1.05


i'm going to test the pull difference on the carrier again some other time. i blew the fuse on the dmm.
there was no difference between taped batteries and the carriers when i tested earlier but i want to make sure.
 
So you removed the 2AA->1D adapters from the equation and nothing changed in your readings? If thats the case, it has to be the batteries. Did you try the battery adapters with both battery types? Then try taping the batteries together (no adapters) with both battery types? If your still getting lower than usual numbers it could be that both sets of batteries are bad, but maybe (for some reason) the P7 just won't run well on AA NiMH batteries :shrug: . It should run just fine. I'm pretty sure a AA NiMH can discharge more than 0.5C in this case.

I'd make sure you don't have added resistance somewhere else. What size wire are you running from the Mag switch to the P7? And plugs between there? Ugly solder blobs or anything? Something is fishy.
 
Drewfus2101 said:
So you removed the 2AA->1D adapters from the equation and nothing changed in your readings? If thats the case, it has to be the batteries. Did you try the battery adapters with both battery types? Then try taping the batteries together (no adapters) with both battery types? If your still getting lower than usual numbers it could be that both sets of batteries are bad, but maybe (for some reason) the P7 just won't run well on AA NiMH batteries :shrug: . It should run just fine. I'm pretty sure a AA NiMH can discharge more than 0.5C in this case.

I'd make sure you don't have added resistance somewhere else. What size wire are you running from the Mag switch to the P7? And plugs between there? Ugly solder blobs or anything? Something is fishy.
Click to expand...

can the volts affect the discharge rate?
i did get 2.9a(4.2v) when the sanyo was 1hr off the charger. 2hrs later it was 2.35a(4.2v)
:thinking:

yeah maybe better with a nimh d(no converters) or lion


edit: 18gauge. is that bad or good?
like this
http://www.radioshack.com/product/i...oductId=2049745&support=support&tab=techSpecs

i'm kinda giving up on this. i did a 3aa taped verses 3aa in converter and there was a .4a difference. i was thinking aha~! then i put the taped ones back in the carrier than got the same as the taped reading. go figure.:whistle:
 
Last edited:
f22shift said:
can the volts affect the discharge rate?
i did get 2.9a(4.2v) when the sanyo was 1hr off the charger. 2hrs later it was 2.35a(4.2v)
:thinking:

yeah maybe better with a nimh d(no converters) or lion


edit: 18gauge. is that bad or good?
like this
http://www.radioshack.com/product/i...oductId=2049745&support=support&tab=techSpecs

i'm kinda giving up on this. i did a 3aa taped verses 3aa in converter and there was a .4a difference. i was thinking aha~! then i put the taped ones back in the carrier than got the same as the taped reading. go figure.:whistle:
Click to expand...

How are you getting those voltage and current readings? Are you taking those real time with the light running? Or are you turning the light off and then checking the batteries then turning it back on to check the current? You need to make sure you get that voltage reading with the light on. I think you said earlier you were doing that though. But your V and I numbers just don't match.

NiMH batteries are capable of discharging at huge rates no matter what they're voltage is. I know that some NiMH D size batteries are capable of 16A discharge.

Your link is to 22 guage wire, which is to the exact same wire that I'm using from Radioshack. I also just finished up my DD build, and at 3.6V i'm only getting 2.1A (3 x D size NiMHs). I've got to find a spec sheet in english to see if thats close enough to spec or if the 22 guage wire is not letting enough current through. I did some digging online, and found some charts that advise for 12V systems running around 4 to 6 amps not to go any smaller than 18 to 20 guage. I'll probably change out that wire for 18 guage if I can find any. That 22 guage is all I had laying around at the time though. I've had this problem before with too small of wire creating a restriction. Its easier to use larger wire than sit around and scratch your head and wonder why your having problems.

I'm still thinking you need to test without the AA batteries or test with a different P7. Find someone with a bench top power supply that you can dial in 3.6 volts and see how much current the P7 is pulling at that point. I got this one:
https://www.mpja.com/prodinfo.asp?number=14600+PS
It has been a huge help with LEDs.

Or swap out the LED for another P7 and see if the numbers change.
 
Drewfus2101 said:
How are you getting those voltage and current readings? Are you taking those real time with the light running? Or are you turning the light off and then checking the batteries then turning it back on to check the current? You need to make sure you get that voltage reading with the light on. I think you said earlier you were doing that though. But your V and I numbers just don't match.

NiMH batteries are capable of discharging at huge rates no matter what they're voltage is. I know that some NiMH D size batteries are capable of 16A discharge.

Your link is to 22 guage wire, which is to the exact same wire that I'm using from Radioshack. I also just finished up my DD build, and at 3.6V i'm only getting 2.1A (3 x D size NiMHs). I've got to find a spec sheet in english to see if thats close enough to spec or if the 22 guage wire is not letting enough current through. I did some digging online, and found some charts that advise for 12V systems running around 4 to 6 amps not to go any smaller than 18 to 20 guage. I'll probably change out that wire for 18 guage if I can find any. That 22 guage is all I had laying around at the time though. I've had this problem before with too small of wire creating a restriction. Its easier to use larger wire than sit around and scratch your head and wonder why your having problems.

I'm still thinking you need to test without the AA batteries or test with a different P7. Find someone with a bench top power supply that you can dial in 3.6 volts and see how much current the P7 is pulling at that point. I got this one:
https://www.mpja.com/prodinfo.asp?number=14600+PS
It has been a huge help with LEDs.

Or swap out the LED for another P7 and see if the numbers change.
Click to expand...

i was measuring the volts with the batteries out. i figure it doesnt make a difference since the end result is the same which is the amp discharge rate changing.

on the wire, i am using 18 gauge. it's thick and annoying to use for modding. i think it's overboard but that's what i have lying around. i also use the wire for the tailcap spring mod. i dont' think it's the wire thickness.

it's probably the carrier or battery.:shrug: i'm going to wait for some kind of p7 driver that runs on 3 cells.
 
f22shift said:
i was measuring the volts with the batteries out. i figure it doesnt make a difference since the end result is the same which is the amp discharge rate changing.

on the wire, i am using 18 gauge. it's thick and annoying to use for modding. i think it's overboard but that's what i have lying around. i also use the wire for the tailcap spring mod. i dont' think it's the wire thickness.

it's probably the carrier or battery.:shrug: i'm going to wait for some kind of p7 driver that runs on 3 cells.
Click to expand...

With NiMH batteries, it shouldn't matter that you were checking the batteries voltage while they were not under a load, since NiMH batteries don't sag like most others, HOWEVER, in your case, since your having such a major modding problem, I would try very hard to measure the voltage and current at the emitter while it was running. I will solder wires onto the emitter leads then use alligator clips with my multimeters to get those readings. This will get you a much more accurate reading. You might actually be getting some sag out of those batteries. Who knows.

That is thick wire. Checking the voltage and current at the emitter would help you figure out if you had other sources (like wire) that were robbing voltage to the emitter. Doesn't sound like that wire is, but some other spots might be.
 
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