Has anyone used a surefire p91 in a Mag?

Hello, All,

I'm wanting to cobble together a really bright, cheap and easy light. The two possibilities I'm thinking of are:

3 cr123s in a 2C maglight, driving a Surefire P91 bulb. Has anyone put one of those bulbs in Mag? If it can be jammed in there without machining (soldering is OK), I think I like this idea. It would be middling bright, with minimal initial outlay.

6 1/2D NiMH cells in a 3D maglight, driving a Pelican Big D bulb. The upside here is that I'm sure all the parts (while expensive) are drop ins. The downside is buying expensive parts and an expensive charger.

Any comments?

Thanks,
Nels

Where do you get 1/2D NiMH batteries?

Also measured a 5 1/2D SL20 battery stick against 3 D cell batteries last week and found the two to be the same length (was thinking of use a 4D MagLED in a 3 cell body). So I'm not sure you'll be able to fit six in the 3D body.

Brighteyez said:

Where do you get 1/2D NiMH batteries?

Click to expand...

A quick google turns up http://www.batterieswholesale.com/products_batteries/nimh/nimh-rechargeable-12-d-3500-hp.htm

I'm sure that the usual suspects, like Mouser and Digikey, would have them, too.

Brighteyez said:

Also measured a 5 1/2D SL20 battery stick against 3 D cell batteries last week and found the two to be the same length (was thinking of use a 4D MagLED in a 3 cell body). So I'm not sure you'll be able to fit six in the 3D body.

Click to expand...

Oops. The specs on that page show a height of 36.5mm for the half-D versus 60.5mm for the full-D. Six of the half-Ds would be 219mm, or 3.61 full-Ds. So, it sounds as if I'd need a 4D Mag with a small spacer.

Maybe rechargeable D cell-sized lithiums in the 3D, or rechargeable C cell-sized lithiums in a 3C Mag, for the ROP option? But that's getting further into complication and expense, I think.

If there is a really bright, roughly 9V PR base bulb I could use in a 2C Mag with those 3 CR123s, or if that Surefire P91 could be adapted with maybe a bit of soldering, I think that might be a simpler and cheaper way to go. So, anyone have a lead on a 9V, PD base superbulb that's roughly equivalent to the P91?

Thanks for pointing out that length problem with the half-Ds.

Nels

You might be able to get away with running the 11 watt ROP-LOW bulb on 3 fresh CR123A primary cells without the bulb instaflashing.
If not, the 5 cell xenon Mag-num Star bulb would overdrive nicely on 3 primary cells and you wouldn't have to worry about heat deforming the stock plastic reflector.

Have you ever seen a SF P series lamp? I suggest you put out a request to members here send you a burned out lamp and see what you can do. Fitting it into a Mag reflector is gonna be difficult. The P91 lamp is cemented into it's reflector and base for optimal focus and beam. Good Luck.

https://www.candlepowerforums.com/threads/74958

I did this with my old Mag 6D and a Surefire P90. I used alkaline D cells. I've since disassembled it and will most likely make the 6D into a ROP.

Procedure:
It's really simple. screw the Mag head all the way down. remove the bezel and lens. Remove the plastic reflector. You will not need it for this mod. Remove the stock PR lamp and screw back on the lamp retainer without the lamp inside. down inside of the lamp holder (where the PR bulb was) I placed a small copper disk/washer. Just place it inside flat. It purpose is to make contact with the contact below on the switch housing and decreases the depth inside. You need to do this because the small P90 spring's length is not long enough to touch the contact at the bottom (the small spring is the one in the middle of the P90). No amount of pulling/stretching it seemed to work for me. It needs to be of a small enough diameter to fit down inside flat and make contact with the copper contact of the Mag switch. The copper disk/washer needs to be thick enough or it will get super hot and melt the plastic. Then place the P90 on top of the bulb holder with the little spring inside (making contact with you copper spacer) and the large spring fits around the outside of the PR base holder. Holding it upright put the lens back on. As you screw down the bezel the lens will put pressure on the lamp and hold it in place. If it is too loose rotate the head up a little bit to increase the pressure to hold it in place. You may have to move the bulb around several times until it makes a good contact and lights. It may take several times putting on and taking off the bezel and lens until you get it just right and it lights. I have found that once you get it set up right it stays in place and works well. The light is now not focusable. Don't mess with the head and rotate in around or you may loose contact and you'll have to readjust. After a little fiddling around mine works great. I have never done a begining to end runtime but it should work well for several hours on the 6 D cells. Since the P90 bulb sits directy against the lens, I replaced my plastic one with a borofloat from flashlightlens.com so it won't melt. It's a completely reversable mod.

Lumenhound, overdriving a five cell bulb sounds like a great starting point. Can't beat it for easy.

The 11W ROP low should draw about 1.22A at 9V. That sounds as if it wouldn't be too much for the cr123s: I seem to recall that they're rated for a maximum sustained draw of 1.5A. I'm guessing that would still require one of the aluminum reflectors, like the one I spotted at Lightedge?

As for turning it into a flashbulb, isn't it supposed to operate on 6 Alkaline cells? They'd give a nominal 9V, though they'd have a lot more internal resistance, which would limit the startup surge. Dreaming up some sort of current limiting circuit would take this out of the trivial, drop in category, I think.

NotRegulated, I was hoping it would be that easy. I gather that the inner spring is one contact, and the outer spring is the other? It sounds as if the outer spring of the P90 is just right to make a decent contact with the outer post.

I think that the reason that you needed the copper disk is that the inner contact on my ancient Mag is a tiny button. It would probably sit right in the middle of the P90's inner spring. I wonder if I could tear the guts out of an old Mag bulb and build up the center contact inside to make an adapter.

Thanks for the responses, guys! This is starting to sound plausible.

Nels

The ROP-LOW is a 6.0 volt bulb that was intended to be powered by a large 6 volt gel cell battery.
I pulled a ROP-LOW bulb out of a spare #3854 package and tested it on 3 fresh primary CR123A cells. After a minute it had settled in at 1.8 amps with 6.8 volts across the batteries. No instaflash problems with this robust bulb.
A 2 amp draw on 1400 ma hour rated primary CR123A cells is within safe limits.
You could expect about half an hour continuous on high quality cells.
Check out Silverfox's CR123A battery shootout thread here for some excellent brand comparison test results.

The standard plastic Mag reflector will melt from the heat of the ROP-LOW bulb. See this ROP-LOW heat torture test thread.

A 5 cell xenon or krypton Maglite bulb on 3 CR123A cells is very easy but there are other bulb options for a 2C/3 CR123A combo. Check out this thread with beamshots from last October.

Plenty of good reading there.

Referring back to the dimensions, you can only get 5 1/2 D batteries into a 3D mag with the stock switch. Not quite enough for a decent ROP. I tried the same route, spent quite a bit of cash to get decent rated 1/2 D NIMH, but they never got to give a decent light level. ( I just transplanted 11 of them into a 6D mag for a polaris clone that doubles as a decent size baton)

Go for a Mag85, it's childs play to make a decent battery pack, and a decent charger should only cost about 8 UK pounds.

Plus, on a related note, the best rated NIMH 1/2 D I could find were 2100 mah. It's cheaper to buy 2500 MAH rated AA size.

Just my ha'penny's worth.

Surefire bulb _does_ work in the Mag.

So, I tried an experiment, and it looks as if the Surefire bulb can be reliable and practical in the Mag. I bought a Surefire bulb, made an adapter and tried it in one of my Mags. It works great.

To make it work, I took a 3/4'' copper tack, cut it in half (leaving 3/8'', discarding the point), and stuck it through a bit of cork which fit nicely into the bulb socket. I took the bit of tack which was sticking up out of the cork and jammed it into the inner spring of the Surefire bulb. Now, when I followed NotRegulated's instructions, above, the wide, flat head of the copper tack made secure contact with the Mag's inner contact, inside the PR socket, and the outer spring made contact with the screw-on collar which used to hold the bulb. The cork bit prevented the inner spring and tack from shorting against the outer part of the socket. The total cost of the adapter was near enough to zero.

My experiement put a P61 into a 4D mag, and it makes a really practical, bright light. The only problem so far is that because I took off the reflector and didn't replace it with a shim, the bezel no longer compresses the o-ring, so it's no longer water tight around the lens. I'll cut a ring out of a CD to fill that space and fix the problem. The P61 gets hot, but I've left it on for a minute or two and no harm to the plastic lens yet. I suspect that if I left it on long, it would do harm, and that P91 I want to use would do harm sooner.

I think I'm going to go with the P91 and 3x123 combo in the 2C for my bright, cheap, easy kludge. My plan is that this is going to ride around in the glove box most of the time, and won't be used from one month to the next, once I've gotten over the novelty of the new toy. This means that rechargeables are a bad plan because they'll self-discharge, while the CR123s are ideal, because of their long shelf life.

The P91 and the ROP low should be roughly comparable in terms of current draw and therefore, hopefully, brightness, according to the ``How much current in your bulb?'' thread. It looks as if I need to look at cost and other considerations to choose between them.

The P91 will only cost $27 or so, plus the cost of the borofloat lens, which is the only part I'll have to buy. The ROP low would require an aluminum reflector, as well as the lens, so the first cost would be about the same. After the first bulb change, the ROP option would be cheaper. Since the P91 is supposed to last about 25 hours, per Surefire, that's at least 60 battery changes (at three battery changes in an hour) per bulb on average. Since I don't plan to put a lot of hours on this in a year, I'm using the P91 rather than the ROP low for the potentially greater reliability: it's designed to run on three CR123s.

If I were going to be using this a lot, then rechargeables and the lower replacement cost of the ROP low bulbs would be the sensible combination.

Now, the only thing I need to do is order a few glass lenses and go buy that 2C Mag and the P91.

Thanks for the advice and the pointers, everyone.

Nels

The 2C Maglite arrived, and since I don't yet have a P91 I took Lumenhound's advice and stuck in 3CR123 and a 5 cell krypton bulb. It out-throws everything else I have. I compared it to the P61 in the 4D Mag, and the P61 lights up trees (green-black Sitka spruce) 100+ feet away. The new toy with the over driven 5 cell bulb lights up a bright white spot in the wall of yellow light the surefire bulb puts on the tree. In other words, there is a really tight, bright hotspot, and a bit of dim, broad spill. 150+ feet away, the over driven 5 cell bulb is still bright on the Sitka spruce, and the P61 has faded away.

It's probably worth mentioning that it's only half past midnight, and it's only about half dark out. We'll have some real darkness before bedtime in about three months, and those lights will be visible a bit farther then.

I'd say that the over driven 5 cell is probably putting out no more total lumens than the Surefire P61's 120 (probably a good deal less!), but that wide, deep reflector is more than making up for it in the tiny hotspot. Out to about 100 feet, the Surefire bulb and reflector combo is probably more useful, because it adequately lights up a larger area, while the over driven 5 cell is making a handkerchief sized patch bright as day. The Magled 4 cell drop in is dimmer than both, of course, but again, that big reflector gives it a really tight hotspot and great throw.

Now I'm conflicted: should I go ahead with my original plan of putting a P91 in there, and give up some of that lovely throw for a really bright wall of light, or should I stick with the current setup? I guess the real question is: ``Will my wife beat me up if I spend another $30 on a light bulb?'' I'll report back on how the P91 works when I get over the bruises.

Nels

EDIT
============
Here are a couple of things I was too tired to add last night:

Instead of buying the borofloat lenses from flashlightlens or lighthound, I bought some magcharger lenses from zbattery.com. Their web site claimed that they would fit, and I figure that they should be able to take some heat, though they may not be in the same class as the borofloat lenses. They cost only half as much, so if they work, it's a great budget resource.

Zbattery was right that they would fit (well, nearly right, two out of three): the lenses fit the new 2C mag and one of the two old 4D mags, but not the other oldie. My two old mags are old enough that they don't have the ``D'' in the serial number (more than twenty years old). So, the 4D with the P61 and the 2C which will get a P91 have a magcharger lens. The magled drop in is in the other 4D, with the still-clear plastic lens from the 2C.

Another thing to mention is that the old plastic lens is an adequate spacer to replace the reflector in the magfire 4D/P61 light. Putting it outside the glass lens is enough to make the lens a tight fit in the bezel. If the plastic lens shows signs of heat damage in the middle, I can cut out the middle.

nelstomlinson said:

I'll report back on how the P91 works when I get over the bruises.

Nels

Click to expand...

That's the spirit Nels, take one for the team. :twothumbs
When in doubt, buy both!