The torch in question was a present from my son and has been engraved. After reasonable use the plastic aaa battery holder has disintegrated but I would like to keep the torch for sentimental reasons. I figure that a 25500 lithium ion cell will fit with room to spare. I would like to get an led which has two chips in series then I can use a boost regulator to power it. I figure about 2-3A led current will give a life of an hour or so, and give plenty of lumens. Have lathe and mill so am not afraid of turning up metal parts for better heat sinking etc.
So basically am looking for advice as to which LED and which driver. The inside diameter of the torch is 26mm and the original LED sits in a 30mm recess.
Lensers aren’t the easiest to mod tbh. They have the + and - at the end of the battery carrier, so if you want to use Li-ion, you’ll have to solve this. Either by a new carrier, or somehow mod the switch end to make the body carry the - current.
The switch will need modding, as it doesn’t use a driver, but the switch has some current limitation modes.
As for Leds, you’ll need to solder a new one on. Not sure what the old P7 used, was it an X-RE?
The p7.2 uses an XP-G2. I’d say either one of these, the new XP-G3 or maybe an XP-L HI. Although the latter may limit throw compared to the others, but would likely offer more lumens.
I have the P7, and I want to mod it very much. It is an excellent body and it is not utilized at all. As previously mentioned it is extremely hard to mod.
The emitter is sitting on a post and needs to be large so it can be soldered to the wires. The main emitter is XRE I think and it has a rather large package. Some people have cut the MCPCB to some size and then inserted inside and wired up. Difficult stuff. Further complicating with array leds inside is not wise according to me. The body does not need such power, nor can it cope with the heating. The best emitter would be XPG3 5000K 90+ cri, or a Nichia 219c direct driven.
The battery compartment is also very proprietary. And it is notoriously difficult to mod. Horrid stuff.
This is why after the P7 all my lights are easily modified with off the shelf parts. I know the P7 is one of my most beautiful lights, and I would love to have it with a lithium battery and a powerful emitter. If you somehow manage to succeed in modifying please write up.
@ chicken Drumstick
Thanks for the reply. I was reading about how to mod a P7 on the internet and how awkward it was when I came accross the excellent info post here, https://budgetlightforum.com/t/-/23020 .
The original LED was an XR-E, but I’m happy to swap it out. I have soldering, pcb and electronic design skills and am willing to use them for this. I will be happy if the outside remains unaltered, but the inside can be completely changed. The reason I asked about 6v or two led in series configuration is that it would be easier to use a boost convertor for power. The P7 uses a couple of switched resisters on the lower pcb so the torch output was never even over the relatively short 4aaa battery life.
My issue with the single led solutions you suggest is that the Voltage across the LED is high relative to the normal battery voltage. I have also noticed that the voltage figures given are at 85C, which is all very well, but I suspect the voltage across the LED at normal ambient, say 20C is almost equal to that of a half discharged Li ion cell, leaving no room for current regulation. Do drivers exist which will buck and boost?
Also seem to be having trouble removing the LED/mount/other electronics from the aluminium tube. I have removed the white plastic LED clamp/cover with its star head screws revealing the LED sitting on an aluminium pillar in the centre of it. I thought these just screwed in. It may jut be tight or it could be bonded. If bonded as I suspect I have two options, a debonder chemical or machine it out (possibly just the centre) with a mill, destroying the insert.
OK I have just managed to remove the LED holder and its electronics from the tube. It is threaded but sealed with what appears to be an epoxy. I used a hot air gun and heated it to around 300C before it would undo. Outer tube is undamaged so its all looking rather good.
reason for mod is that torch was a gift and has sentimental value far greater than its actual value. See first post.
Have disassembled pill (first technical torch term !!) and removed pcb (22mm dia) which just has two resisters, 3.6 and 2.4 ohm. So basically torch is just resister(s) and LED. Looks like 25500 lithium ion cell will fit spot on. Just need to sort out suitable driver board and LED … .
After some heat from a hot air gun (approx 300C) (oring was removed for this)
I think I have decided to use an XM-L2 Cree LED emitter, with a 25500 cell. I have ordered a few controllers as I am undecided whether to keep the original switch which is bright/dim/off or change it for something more exotic.
I thought i would narrow the post to 3.5mm, for the top 2-3mm. The contacts I would solder with 22 gauge copper wire, formed to run outside the post, which would also help remove the heat. It should be possible to use the same white plastic locator/clamp as per original. So from the outside the torch would look the same except that the LED will not have a silver ring.
Edit : I have had a rethink about that and I think I will remove the aluminium post and tap a central hole, M6 or M8. I can then turn up a piece of copper rod, threaded at the end to fit (may find an old bolt or set screw). Then I can solder the LED thermal pad and negative to the copper leaving just 1 wire for the LED positive. This would seem to have many advantages, better thermal dissipation and much lower thermal resistance (no icky thermal paste), 1 single connection wire, easy removal and replacement of post/LED in future if necessary. And it will still look original
May also have changed mind about 2550 cell as capacity is not so different from 18650 which I think can fit.
From what I have read using 7135’s is good. It looks like these can be controlled by connecting the Vdd pin to ground to turn them off. So I appear to have two options. To use the original P7 switch to enable them or to use a small microprocessor to do so. The nice thing about using a small chip is that it could be programmed in very useful ways. I thought something like a 10F320/322 would make life easy. I figure that a short push should allow on at 1 brightness level, two short pushes in succession another. A long push with the light off would set the torch to maximum. But a long push with the light on would allow programming of the light to a desirable output level. So after a second or two the light output would increase to maximum then fall to minimum and continue to cycle until the button was released at the desired light level. This would be stored in flash memory. Also using a microprocessor would allow the beam to flicker as the battery life reached its end. Varying of the level would be done by using pulse width modulation of the 7135’s Vdd pins. As this could be done at 2-300Hz no flickering of the light output would be detectable by the human eye. The only parts it would appear to need are the micro chip, some 7135’s and maybe a resister. Possibly a capacitor to keep the micro stable.
are you needing multiple light levels or would 2 suffice?
if you want to keep things nearer original and just have off, dim and bright you could just use the switch itself to turn the 7135’s on or off,
dim could activate a couple of 7135’s and bright would activate as many as you liked.
cant see any need for a FET as the switch would only be carrying a few milliamps.
alternativly you could get one of the programmable 7135 drivers and use that for the high and just a single 7135 on the low. not sure how your switch works but you should be able to change modes when on high if required
Thankyou for your comments. My first thought was to do as you suggest with the original switch. But I have come to think it would be nice to have the extra range of light output available, especially as with up to 2.5A the torch may get too hot. I have some LG HG2 18650 cells and they appear to be ideal - I even tested them at 3A continuous and they lasted over an hour. Also the original switch does not seem very good mechanically, it is quite large (14mm height) and because the 18650 is going to be a squeeze lengthwise I am not sure I want to commit myself to a design which will have to be reworked if/when the switch fails. It is not a standard part afaik.
Have ordered several different types of switches but may go with a reed switch and a magnet in the push button. These are very hardy and completely sealed against the environment.
As to the FET, it is history. I have never used the 7135 before but on looking at the data sheet control can be simply implemented using the Vdd pin.
I have ordered some premade driver boards of various types but I kind of like the idea of setting the output level where I want it in a given situation.
Yup thats it!! Two dodgy resisters. Difficult to get cheaper. Quite like the optics of the torch though.
Have you got some pics of the switch? Might help with options
If your wanting to go with magnets you might want to use a hall switch instead of a reed. Reeds can have a tendancy to weld up if used for high current. Plus can be susceptible to damage from being dropped
For reliablity those resistors are fairly good. Not really anything to.go wrong and limit current to acceptable.levels for most.
Its only if you want real regulation and to modes that you need drivers