P7 6D mag.

Is it possible to run a P7 Direct drive in a 6D mag on primaries?..... 3S x 2P

What I have is a 6d mag and access to 'free' primaries ( I would be using the light at work) Not realy interested in messing about connecting a bunch of drivers, or multi mode wizardry together. Just want a stock switch, cut down stock reflector ( if they dont melt) and a use a heat sink bought from somewhere here on CPF, to do a real simple mod.

So I thought I doubt that primaries could handle the ~3A required for the P7, but If I put 6 in a 6D, and had 3 primaries in series, and another 3 in series running in parallel ( there is battery rattle in the light, so room enough for wires to series/ parallel. Would that be enough capacity to work reasonably well?

Of course if there is a SIMPLE driver out there, I woulden't mind popping one in, but If it all gets to technical, I'm a Direct Drive hotwire incan kinda guy, so I'd just stick with those for now.

If you could heatsink the P7 enough you could probably even direct drive it on 6D Alkalines. It's be close to double the Vf and ~5.5A. I've tired it for 5 mins and the P7 didn't blow and still works.

Unless you think of a way to turn the battery pack to 2S2P it's unlikely that you could run the P7 for long on 6Ds in direct drive.

It would be easy to get 6 alks into a 3S 2P pack.

I'd just use the kit we have here at work to solder & wire 6 together so that a string of 6 cells were connected 3S2p with two wires, and insulte the first 3 from the last 3 in the middle, and use the ultra thin ( wide )tape we have here, or shrink wrap to hold the pack together to fit it in the light.

I'd simply make a few packs at a time and bin them when they were done....I could do all this at a tech's work station in a few minutes.

The real question is would 3S 3P duracell D's work with a P7 on say a H22A or simmilar heat sink?

If so I will order a P7 or two, and a heat sink.

Interesting that 6 can be in series, but I would have thought for longevity its not the way to go.

Raoul_Duke said:

It would be easy to get 6 alks into a 3S 2P pack.

I'd just use the kit we have here at work to solder & wire 6 together so that a string of 6 cells were connected 3S2p with two wires, and insulte the first 3 from the last 3 in the middle, and use the ultra thin ( wide )tape we have here, or shrink to hod the pack together to fit it in the light.

I'd simply make a few packs at a time and bin them when they were done....I could do all this at a tech's work station in a few minutes.

The real question is would 3S 3P duracell D's work with a P& on say a H22A or simmilar heat sink?

If so I will order a P7 or two, and a heat sink.

Interesting that 6 can be in series, but I would have thought for longevity its not the way to go.

Click to expand...

If you can make the pack then it'll work. The LED will be fairly safe as with 3 NiMH you're rarely hitting the 2.8A rating, with alkalines you'd under driving it at best due to their inability to deliver high currents and account for voltage sag.

I don't deal with thin wires very often with high powered mags as sometimes the current can overwhelm the wire.

tebore said:

If you can make the pack then it'll work. The LED will be fairly safe as with 3 NiMH you're rarely hitting the 2.8A rating, with alkalines you'd under driving it at best due to their inability to deliver high currents and account for voltage sag.

I don't deal with thin wires very often with high powered mags as sometimes the current can overwhelm the wire.

Click to expand...

I was going to use wire rated at 10A @ 24V...so no concerns there.

I meant thin tape to hold the pack together, and keep the wires, on the cells.
Solder the primaries end to end, for lower resistance, and to keep them together, and solder the wires for 3S2P.

Might not be worth it, as I was only going to try this if it would power the LED well enough.....not even sure what d cells cappacity is at 1.5A or whtever it could provide.

I have a bunch of Cells.....Varoius High discharge NiMi, emoli in both sizes, aswell as Li-ion in all shapes and sizes....but I thought it may be eaisier for me to use the primaries here, as a cheap light that i could lend out and forget about for a while, if It just sat around; & so I could save the cool cells for my hotwires.

How hot do P7's get...Have also concidered attaching a P7 straight on to an Emoli 26700 and connecting a fuse and switch, and then putting heat shrink around the whole lot for a mule style cheap light. The LEd might get to hot for the cell though....but they perform better when hot...I will have to look at the data sheet again to see how hot they can get.

do P7's need to be islolated on heat sinks...Ie is the base +, -ve or neutral.

Thanks for the replys.

They do need to be isolated.

IMHO they don't run that hot. It all depends on how hard you drive them
At low currents they are really efficient. As you push up it gets less and less and thus gets hot. A DHS type sink powering the P7 to spec (3.5-4v and ~2.8A) will be enough.

Wouldn't it be easiest to use 3 D spacers instead of making custom packs? You'd have to change the batteries twice as often but it would be a lot more convenient.

If you do as you say "at least I think I know what you are trying to dooo:" by running 3d s in parallel with another 3d s then it should work. Drawing 1.5 A out of Ds is completely possible "though a little out of what they like" in my max alkaline powered light "30 watt 10 D light I use 10 D cells to make 15 volts while pulling 2.5 A out of them. The bulb wants 12 volts, so with the voltage sag under the high drain rate I more or less come right in with the correct voltage. The light will run about 30-45 minutes so 1.5 A shouldn't be that big of a deal, well it's a lot nicer than what I do to them:devil:.

A P7 hits about 70 lumens/watt at high currents. The theoretical max where all electrical energy goes to light (thus, no heat) is 240 lumens/watt, so you're looking at about 70% efficiency, so at 10W input, 3W will be converted to light, and 7W will go as heat.

This means you need a heatsink that achieves 7W at fairly low temperature differences (I'd be happy with 30'C). However, generally speaking you don't see this kind of rating, so keep a low resistance thermal path to the outside of the light and chances are you'll have enough surface area.

Personally I'd go for DD with 4 D cells, rather than fart about with trying to make parallel strings in a mag. Under 2A+ load, the alkies will sag horribly, so the 6.4V under rest fresh alkies measure should drop right down to a more realistic voltage. A 2 stage mod with a beefy resistor wouldn't be a bad idea, as the lower draw would enable the alkies to be running at kinder levels (even 500ma should give you 180+ lumens), which they greatly prefer.

Juggernaut said:

If you do as you say "at least I think I know what you are trying to dooo:" by running 3d s in parallel with another 3d s then it should work. Drawing 1.5 A out of Ds is completely possible "though a little out of what they like" in my max alkaline powered light "30 watt 10 D light I use 10 D cells to make 15 volts while pulling 2.5 A out of them. The bulb wants 12 volts, so with the voltage sag under the high drain rate I more or less come right in with the correct voltage. The light will run about 30-45 minutes so 1.5 A shouldn't be that big of a deal, well it's a lot nicer than what I do to them:devil:.

Click to expand...

Your right...Thats what i hope to try....10 D's...that must be a big light.

thanks

My thoughts on a number of questions raised:

First off, if you use an anodized heatsink, that will isolate the base of the P7 and you don't need to do anything else.

Regarding the power source aspect, running 6 D cells in a 3S2P direct drive situation should work fairly well with a P7 led. You didn't state how you'd often use the light, but if it was intermittent then the D cells would give you close to full output for a long time. In a continuous runtime test, the time to 50% output would be fairly short, but you'd have an extremely long "tail" of gradually decreasing (but still useful) output.

In my opinion, running direct drive with 4 D cells is asking for trouble, or at best a shortened useful life for the LED. The voltage of D cells holds up pretty well under high (1+ amp) current drain. You'd be seriously overdriving a P7 for a significant period of time with a 4S setup.

Why not disassemble a 6v lantern battery and use 4x F cells?

MorePower said:

My thoughts on a number of questions raised:

First off, if you use an anodized heatsink, that will isolate the base of the P7 and you don't need to do anything else.

Regarding the power source aspect, running 6 D cells in a 3S2P direct drive situation should work fairly well with a P7 led. You didn't state how you'd often use the light, but if it was intermittent then the D cells would give you close to full output for a long time. In a continuous runtime test, the time to 50% output would be fairly short, but you'd have an extremely long "tail" of gradually decreasing (but still useful) output.

In my opinion, running direct drive with 4 D cells is asking for trouble, or at best a shortened useful life for the LED. The voltage of D cells holds up pretty well under high (1+ amp) current drain. You'd be seriously overdriving a P7 for a significant period of time with a 4S setup.

Click to expand...

Thanks For reading through, and answering some of the quiestions that I made.

I would mainly have it for use at work...but only realy for intermittent use....maybee a quick blast.....But if needed...it would be good to know it could be run right down for a long time with some usefull light.

Best bit is that the cells would be free so replacements are fairly easy....no charging issues....just use and forget.

I could also leave it sitting around incase I needed it ( might have to check the cells every few months for leakage, but I would probably go through a set of cells in that time frame....So this might work quite well.....If it worked out OK I would probably leave one in the girlfriends car, so It would be as she needed it....probably not to often....but I saves on having to check on self discharging nimh...and my girlfriend is not interested in using the torches she knows she could overdischarge and kill the cells.

On the isolated base for the heatsink...why does it need to be isolated...I remember reading this...and now have had it confirmed that it does, thanks, I would assume that the base of the LED is opposite polarity to the heatsink & body of the flashlight?

Raoul_Duke said:

I would assume that the base of the LED is opposite polarity to the heatsink & body of the flashlight?

Click to expand...

Yep, though ideally the whole heatsink should be isolated (e.g. by hard anodization). For my 6D P7, I used an HAIII DHS heatsink, and it worked just fine. Note that I ran it off 4x F NiMH, not Alkaline, however, and I used a simple 2.8A 8xAMC7135 1-mode driver.

marschw said:

Why not disassemble a 6v lantern battery and use 4x F cells?

Click to expand...

Do you have any linkage to where I would get some of those???

Are thay the ones that are to be treated gently....break easy?

Raoul_Duke said:

Your right...Thats what i hope to try....10 D's...that must be a big light.

thanks

Click to expand...

It's quiet huge, pic in 2008 collections, just a note if you try the same type of setup you will see a very small amount of under drive I think, on the voltage meter it looks good but in reality the beam is slightly orange "though still very bright:twothumbs"

Raoul_Duke said:

Do you have any linkage to where I would get some of those???

Are thay the ones that are to be treated gently....break easy?

Click to expand...

F cells are just like D cells but 1.5x as long. Lantern cells are widely available, and have 4 F cells inside them. They're often bundled with floating spotlights. Examples here. Note that some cheaper ones use D cells instead and have empty space inside. So, if there are multiple brands available, and one is heavier than the others, go for that one.