# Surefire P91 Bulb and 18650 Cells ?



## Bob96 (Feb 9, 2010)

I run my P61 with 3 primarys or 2 INR16340 cells. Both work out fine. I wanted to try it with my two 18650 cells. I have read posts saying this is fine and others saying these cells will shorten bulb life or even flash the bulb? I know that the larger cells can supply more amps but they are the same voltage? Is it that the P61 can and will draw more current flow from the 18650 cells.


----------



## fivemega (Feb 9, 2010)

Bob96 said:


> I run my P61 with 3 primarys or 2 INR16340 cells. Both work out fine. I wanted to try it with my two 18650 cells. I have read posts saying this is fine and others saying these cells will shorten bulb life or even flash the bulb? I know that the larger cells can supply more amps but they are the same voltage? Is it that the P61 can and will draw more current flow from the 18650 cells.



*I am sure you mean P91 and 2 IMR16340 

Powering a P91 with 2 protected 18650 will severely overdrive it and will reduce bulb life.
Using pair of IMR 18650 will most likely kill the bulb.
Not a good idea for $35 bulb.*


----------



## Bob96 (Feb 9, 2010)

Yes I meant the P91 bulb


----------



## socom1970 (Feb 9, 2010)

No way I can oppose FM's assessment of the situation...

That said, I have been using my P91 LA with 2x18650 cells on and off for about 3 years with no problems at all. Extremely bright and still going strong.

I definitely would not use IMR's with the P91, though.


----------



## Rjkpsmith (Feb 10, 2010)

Well, I suppose that it might vary from bulb to bulb, but many people seem to have no problem running the P91 on 18650's or even IMR 18650's... an example would be here - http://www.youtube.com/watch?v=g8qg4LwcxDU

Also here is a video where MrGman and BigChelis show a p91 with both IMR and Li-ion batteries in action. http://www.youtube.com/watch?v=oEU2gGSDYxU

So it can be done, but it does probably decrease bulb life and increase the risk of instaflashing. :shrug:


----------



## bigchelis (Feb 10, 2010)

I use my P91 with 2 IMR 18650 cells. Please note that while I have been lucky with about 11 hours of use other folks here have them die the second they do it. Others have also had them last for a very short time and like FM said its a $35 dollar bulb and at your own risk.

Here is my P91 with 2 IMR 18650 cells performance: The real OTF lumens

SureFire P91_____________Solarforce w/AR Glass__2XIMR18650__473.4_____1 sec
SureFire P91_____________Solarforce w/AR Glass__2XIMR18650__445.3____10 sec
SureFire P91_____________Solarforce w/AR Glass__2XIMR18650__411.2____30 sec
SureFire P91_____________Solarforce w/AR Glass__2XIMR18650__396.4____60 sec
SureFire P91_____________Solarforce w/AR Glass__2XIMR18650__381.7___120 sec
SureFire P91_____________Solarforce w/AR Glass__2XIMR18650__383.1___180 sec


And here is what it does if you use 2 AW 2600mAh 18650 cells:

*Surefire 6P w/ 18650 extention____P91___________2 AW 2600mAh__________420.8________1 sec
*Surefire 6P w/ 18650 extention_______P91_____________2 AW 2600mAh_____________393.1________30 sec
Surefire 6P w/ 18650 extention_______P91_____________2 AW 2600mAh_____________385.4________1 min
Surefire 6P w/ 18650 extention_______P91_____________2 AW 2600mAh_____________379.2________2 min
Surefire 6P w/ 18650 extention_______P91_____________2 AW 2600mAh_____________376.9________3 min
Surefire 6P w/ 18650 extention_______P91_____________2 AW 2600mAh_____________373.8________4 min


----------



## nzgunnie (Feb 10, 2010)

My P91 lasted about 10 seconds on a pair of 18650s...

Might have been a dodgy bulb, might have simply been overdriven and , I am not sure.

Use at your own risk.


----------



## fivemega (Feb 10, 2010)

*Each battery might be different than others, each charger might charge higher than others, each bulb might be different than others, each switch might be different than others, each set up might be different than others and...
Do you think all of your batteries comes out of charger with exact same voltage as Mr. OP?
Do you think all your batteries sag exactly like your friends?
Do you think your switch has exact same resistance as your brothers?
Do you think all bulbs are created same?

I need to repeat this one more time.
Nothing is created same.

So go ahead and run your bulb with anything you like.*


----------



## kramer5150 (Feb 10, 2010)

fivemega said:


> *I am sure you mean P91 and 2 IMR16340
> 
> Powering a P91 with 2 protected 18650 will severely overdrive it and will reduce bulb life.
> Using pair of IMR 18650 will most likely kill the bulb.
> Not a good idea for $35 bulb.*




Curious.... is it any safer for the P91 using higher resistance (saggy for lack of a better term) 18650 cells?

:thinking:


----------



## cernobila (Feb 11, 2010)

Mine lasted about two hours on two AW 2.6A 18650 cells, it exploded in to a dust of glass inside the bezel, damaging the front lens......


----------



## Outdoors Fanatic (Feb 11, 2010)

cernobila said:


> Mine lasted about two hours on two AW 2.6A 18650 cells, it exploded in to a dust of glass inside the bezel, damaging the front lens......


Ouch!

Sorry to hear about that...


----------



## Fusion_m8 (Feb 13, 2010)

My P91 lasted about 20secs on 2 fresh off the charger IMR18650s, the glass of the bulb was charred black and blue after that. :duh2:

During that 20secs it put out way over 500lumens! It made my Wolf-Eyes Rattlesnake EO-13v look dim!


----------



## nzgunnie (Feb 13, 2010)

Fusion_m8 said:


> My P91 lasted about 20secs on 2 fresh off the charger IMR18650s, *the glass of the bulb was charred black and blue after that. :duh2:*
> 
> During that 20secs it put out way over 500lumens! It made my Wolf-Eyes Rattlesnake EO-13v look dim!



Yep, that's what mine looked like too.


----------



## fivemega (Feb 13, 2010)

nzgunnie said:


> My P91 lasted about 10 seconds on a pair of 18650s...


*$3.50 per second bulb life.*



cernobila said:


> Mine lasted about two hours on two AW 2.6A 18650 cells, it exploded in to a dust of glass inside the bezel, damaging the front lens......


*$17.50 hours per hour.*



Fusion_m8 said:


> My P91 lasted about 20secs on 2 fresh off the charger IMR18650s, the glass of the bulb was charred black and blue after that. :duh2:!


*$17.50 per seconds.*



Fusion_m8 said:


> During that 20secs it put out way over 500lumens! It made my Wolf-Eyes Rattlesnake EO-13v look dim!



*My $9 WA1111 puts out more than 800 bulb lumens for over 10 hours bulb life and that is less than $0.90 per hour.*


----------



## polkiuj (Feb 14, 2010)

I dunno about 18650 but I've been running mine on 2 x IMR 18500 without problems. Love that extreme output but I understand that I'm overdriving an expensive bulb. If it blows, I'm OK with that since I already know that there is a chance of that. No risks no fun eh?


----------



## pete7226 (Feb 14, 2010)

Ive run 2 P91 on 2x18650 2200 mah with never a problem and have yet to burn out a bulb. Approaching 10 hours of use in both lamps now


----------



## parnell (Feb 15, 2010)

I have a newb question. I understand that this has probably been answered elsewhere, but since this thread is open....Does it overdrive the bulb because there isn't enough resistance or sag or both with just two cells? What about the imr16340's?


----------



## ShineOnYouCrazyDiamond (Feb 15, 2010)

fivemega said:


> *$3.50 per second bulb life.*
> 
> 
> *$17.50 hours per hour.*
> ...



FM - you are just having way too much fun with this thread..... 



parnell said:


> I have a newb question. I understand that this has probably been answered elsewhere, but since this thread is open....Does it overdrive the bulb because there isn't enough resistance or sag or both with just two cells? What about the imr16340's?



Having blown a few MN20 LAs in a light with some IMR 18650s and IMR 2x2500 and ruining some KT1/2 heads I understand where people are coming from. With IMR16340's and the P91 you should be fine. I've had a P91 running for a while on 16340s with no problems. I've also run in on IMR18500 cells, but started it up with an AW SoftStart so that may have made the difference.


----------



## c0t0d0s0 (Feb 15, 2010)

With IMR cells and P91, switch resistance comes into play. Measure yours, you might be surprised.


----------



## cernobila (Feb 16, 2010)

cernobila said:


> Mine lasted about two hours on two AW 2.6A 18650 cells, it exploded in to a dust of glass inside the bezel, damaging the front lens......



......and I was using the AW softstart/three level switch at the time.....


----------



## yazkaz (Oct 7, 2010)

I have been repeatedly advised not to use 2x3.7V power source to the P91 because its voltage rating is actually 6V, not 7.2V.
Can someone tell me if the MN11 has the same specs as the P91? Ran an MN11 on my M3 with 2x17670 for a few seconds and the hotspot was blinding white.
If the MN11 is similar to the P91 in specs then I'll just revert to the alternatives from LF.


----------



## Chrontius (Oct 7, 2010)

I've used a P91 with 2xIMR 16340 for at least a half-dozen (but no more than a dozen) battery charges as a short-burst light. It does the job admirably, shines like the sun (for its size), and has gotten past the "infant mortality" range, so I'm entirely comfortable relying on it for daily carry.

How much does the P91 pull down the IMR-16340 cells' voltage?


----------



## ampdude (Oct 7, 2010)

yazkaz said:


> I have been repeatedly advised not to use 2x3.7V power source to the P91 because its voltage rating is actually 6V, not 7.2V.
> Can someone tell me if the MN11 has the same specs as the P91? Ran an MN11 on my M3 with 2x17670 for a few seconds and the hotspot was blinding white.
> If the MN11 is similar to the P91 in specs then I'll just revert to the alternatives from LF.



Yes, the MN11 is similar to the P91 as far as voltage spec rating. You may see bulb blackening over time instead of it going poof. It all depends on how well the bulb was made, the newer ones tend to be better in my experience.


----------



## jellydonut (Oct 7, 2010)

Why not just buy 9V bulbs instead of overdriving 6V or 7.2V bulbs? You know they're gonna blow, what's the motivation?

I'm running a Lumens Factory EO-9 on two IMR 16340s and it's happy as a clam.


----------



## yazkaz (Oct 7, 2010)

jellydonut said:


> Why not just buy 9V bulbs instead of overdriving 6V or 7.2V bulbs? You know they're gonna blow, what's the motivation?
> I'm running a Lumens Factory EO-9 on two IMR 16340s and it's happy as a clam.


6V and 7.2V are the actual lamp ratings
If the bulb has a 9V rating then 3xCR123 or 2x3.7V would mean underdriving it

In order for an incandescent builb to light properly, a little overdriving is needed, otherwise output would be very yellowish

Most LF bulbs (except those with a 4.8V rating) are optimized for LiIon use.
Your EO-9 has a bulb rating of 7.2V at 2A so 2x18650 power source is only slightly overdriving the bulb
Meanwhile a bulb like IMR-9 has a voltage rating of 7V so it is more overdriven when used with 2 LiIons and thus yield more brightness (but shortened lifetime)
FYI a typical P90 is rated at 7.2V/~1.15A but the P91 has a whopping 6V/2.5-2.7A (per CPF testing)

LF bulbs are some of the best alternatives to original SF's when it comes to LiIon compatibility. My only gripe is that they are not halogen-filled (in order to cut operation costs) so they may blacken faster than SF's in the long run.


----------



## ampdude (Oct 7, 2010)

Yea, I've had some LF bulbs blacken over time. I didn't know they weren't halogen filled, I guess that explains it.

I would certainly pay more for xenon/halogen filled bulbs.


----------



## lemlux (Oct 7, 2010)

I use some of my weaker matched pairs of salvaged 18650's for P91's and some weaker matched triplet salvaged 18650's for MN60's and MN61's.

By "weaker" I mean Panasonic, Sanyo, LG and Sony cells with measured capacities between 80% and 90% of nominal original capacity. I further match by % of nominal capacity until voltage drops to 3.6V -- those cells that drop to 3.6V fastest are chosen for these applications.

From time to time I call local laptop repair shops to see if they have accumulated many battery packs prior to their next visit to/from a recycler. If they have any, they are often happy to avoid recycling charges by allowing me to pick them up. I then test and bin salvaged 18650's with capacities ranging from 1800 mAh to 2850 mAh. I toss those cells that can no longer deliver at least 1800 mAh.

No dead P91's, MN60's or MN61's so far with considerable cumulative useage.

My main other use for weak 18650 pairs are in several fixed focus Nordic 2C aluminum lights that I bought en-masse on closeout at $2.97 @ at Radio Shack about 7 years ago. These poor man's alternative to a Mag 2C seem to be happy driving Mag 6-cell Xenon bulbs without damaging the plastic reflectors. Thus, the $3.19 per bulb Frys charges for the bulbs are the only expenditure I've needed to make to keep the Nordics useful as emergency loaner lights around the house.


----------



## KevinL (Oct 8, 2010)

Hmm you guys seem to be having a lot of P91 casualties. There's no need to get defensive though. You know how you find the path of the hotwire community? Just follow the road of broken/blown/burned/shattered bulbs. MANY a bulb has been sacrificed to light the way... many enough at the hands of yours truly too 

I have never thought of myself as the lucky type, but my P91 has run fine for hours and hours and hours. I've only ever owned ONE P91 and that's the same one being abused. I use good cells too - LG Chem grade A2 2200's and I always thought this setup was ok. 

I run MN16/MN11/P90/P91 on 17500s as well before I got 2x186500 compatible bodies. No issues either.

If you want tons of light on 2x18650 cheap with much reduced risk of instaflash, go build a ROP. Besides even if it goes poof the bulbs are much cheaper


----------



## lemlux (Oct 8, 2010)

The p91 precautions may be overkill, but the MN60 MN61 aren't. 2 * 18650 / 3 * cr123 delivers a much closer voltage at >2 Amps than do 3 * 18650 / 4 * cr123.

Back in the day I had much worse luck flashing P61's driven by 4 * AA NiMh.


----------



## novice (Oct 15, 2010)

lemlux,
I can do you even better. When I first started playing with AA Nimh cells, I stacked up 5xAA Nimh. "Let's see, these cells are 1.2v, so 5 of them will match this 6v P60 bulb perfectly!" Flash. "Hmmm, I guess I'll play it safe and only use 4." Flash. That's odd. Flash. I then posted my curious experiences, and I believe it was Mr. Happy who first explained the facts of life to me in patient, measured tones.


----------



## jh333233 (Oct 16, 2010)

fivemega said:


> *I am sure you mean P91 and 2 IMR16340
> 
> Powering a P91 with 2 protected 18650 will severely overdrive it and will reduce bulb life.
> Using pair of IMR 18650 will most likely kill the bulb.
> Not a good idea for $35 bulb.*



How come?
Dont P91 suppose to afford 9v?
IMR cells will only get 4.25v max in normal, 4.50 is already critical point(overcharging)

Or the overdrive problem comes from high current supplied from imr?


----------



## hoongern (Oct 16, 2010)

The P91 is not actually a 9V bulb, but closer to 6.8V. (3x CR123s on a P91 sag heavily under load to ~ 2.25V each)

An IMR18650 at that current supplies around 4V each, overdriving the bulb to 8V, and very likely causing a *poof*


----------



## fivemega (Oct 16, 2010)

jh333233 said:


> How come?
> Dont P91 suppose to afford 9v?
> IMR cells will only get 4.25v max in normal, 4.50 is already critical point(overcharging)
> 
> Or the overdrive problem comes from high current supplied from imr?


*P91 is nominally 9 volt bulb because each primary CR123 is nominally 3 volt cell.
You may measure 3.2 volt open circuit of new cell but this will drop to about 2.2 volt under 2.4 Amp draw of P91
So design voltage of P91 is 6.6~6.8 volts with about 30 hours average life.
Each fully charged IMR cell is about 4.2 volt and pair of these may drop to about 8 volts which is already way too much for P91 and MAY flash the bulb.
Li-Co protected 18650 cells have slightly more drop under same load and chance of instaflash is smaller. 
However, some hosts have extra rsistance in totol circuit including, switch, body connectors and bulb springs which MAY save the bulb from flashing but still drives it pretty hard.
Some people reported bad combination, while some other reported reliable in short term. In any case, even if it survies from flashing, bulb life will be shorter than spec.
Say it survives from flashing and has 10 hours life. Cost of operating will be $3.50 per hour for $35 bulb and cost of batteries are not included yet !*


----------



## jh333233 (Oct 16, 2010)

May i raise another question?
P91 generate more light than P90
so P91 have a higher current draw and (voltage?).
but i can still go with P90 safely


----------



## fivemega (Oct 17, 2010)

jh333233 said:


> May i raise another question?
> P91 generate more light than P90
> so P91 have a higher current draw and (voltage?).
> but i can still go with P90 safely



*Current draw of P90 is about 1.2 Amp or half of P91

Each primary under this load has about 2.5 volts, so P90 works fine with 7.5 volts which is just about same voltage of 2 protected 18650 cells under load.
2 IMR 18650 may slightly push or overdrive P90 but it's not as severe as P91

P90 is close to 7.5 volts at 1.2 Amps.
P91 is close to 6.6 volts at 2.4 Amps.

Above figures are rough estimate when run with primaries.
And following figures are rough estimate when run with 2 protected 18650

P90 pushed to 7.8 volts at 1.25 Amps.
P91 pushed hard to 7.6 volts at 2.7 Amps.

Finally here is rough estimate when run with 2 IMR 18650 

P90 pusher hard to 8.0 volts at 1.35 Amps.
P91 pushed severely to 7.8 volts at 2.7 Amps.

Note: all above figures are rough estimate and may varry from one to another depending on health of batteries, size of batteries, type and amount of charging, time of resting, start or end of testing, total resistance of system, ambient temperature of testing, length of testing and ....
*


----------

