Surefire P91 and 2x-AW P18650 -26
- Thread starter tedsm
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Welcome to CPF.
I run mine on 18650's, no poof yet. The bulb is overdriven, so there is always a chance.
I think that the rewards are worth it.
I run mine on 18650's, no poof yet. The bulb is overdriven, so there is always a chance.
I think that the rewards are worth it.
DUQ
Flashlight Enthusiast
Yes the P91 can handle 2 x 18650. Please refer to mdocod's wonderful guide.
http://candlepowerforums.com/vb/showthread.php?t=161536
http://candlepowerforums.com/vb/showthread.php?t=161536
cernobila
Flashlight Enthusiast
Mine lasted about a total of two hours of run time, then exploded inside the bezel damaging the glass lens. This lamp is not designed for two Li-Ion 18650's but most get away with this combination.
Many people use P91 with similar battery bombination such as 2x18650 (2.6), 2x18650 (2.2), 2x18500, 2xIMR16340 and...Will these batteries power the Surefire P91 safely? No?
Some with success and some upset of loosing $30~$35 new lamp assembly.
In any of above battery configuration, P91 is overdriving, running too hot and closer to flashing point. Any slight more overdriving will flash the bulb instantly and any slightly less overdring the bulb will save the bulb for several hours of life.
All depends on battery health, charger ending point, bulb life and total resistance of whole circuit including switch and all contacts.
Remember: not all batteries, not all chargers and not all bulbs are created same and not all hosts have same resistace.
nzgunnie
Enlightened
Mine went on 2x AW18650.
on 2x AW18650.
Every now and then, this question comes up here. And every time, I'll explain again, WHY it is no good to combine 2X Li-ion with the P91:
The P91 has been designed to run from 3X CR123A in, for example, a C3 Centurion or a 9P.
Open voltage (under no load) of a CR123A is around 3.0 Volts.
The P91 draws a very heavy current (around 2.7 Amps!) and for this reason, the CR123A batteries will no longer be able to deliver the full 3.0 Volts per cell to the lamp: the voltage will sag to around 2.2 to 2.3V per cell.
This makes a total of 6.6 to 6.9V for the P91 lamp.
Now let's take a look at 2X Li-ion cells. Hot off the charger, these can give a voltage of 4.2V per cell, this equals 8.4V for 2 series connected cells.
Now compare the 6.6 to 8.4 volts and you'll see: fresh Li-ion cells have a LOT higher voltage. Although the voltage will go down rapidly to around 7.6V or less, it is still too much for the P91. It will either instaflash or have its life severely reduced.
The P90 lamp however, draws only around 1.15 Amps and under this load, a primary CR123A cell will sag to around 2.5V per cell. This equals 7.5V for the P90 with three cells in series. Note that THIS is nearly perfectly compatible with the voltage of 2X L-ion cells (around 7.4 to 7.6V). The short-duration higher voltage is no problem for the P90.
So, if you would like to have a GOOD rechargeable option for your C3 or 9P, forget about the P91, take the P90 instead, and buy yourself some good protected 17500 Li-ion cells. (AW black label).
Note: TWO 17500 cells have the same length as THREE CR123A cells in series. Two of these 17500s are an instant replacement for three CR123A batteries, as long as you use the P90
I ran this configuration from the start, about two years ago. My C3 is still on its first P90.... so yes, it's a durable option (I use this light a lot!)
EDIT: the P90 is also perfectly compatible with 2X 18650. Runtime with 2X AW 18650-26 will be over 2 hours!
Timmo.
The P91 has been designed to run from 3X CR123A in, for example, a C3 Centurion or a 9P.
Open voltage (under no load) of a CR123A is around 3.0 Volts.
The P91 draws a very heavy current (around 2.7 Amps!) and for this reason, the CR123A batteries will no longer be able to deliver the full 3.0 Volts per cell to the lamp: the voltage will sag to around 2.2 to 2.3V per cell.
This makes a total of 6.6 to 6.9V for the P91 lamp.
Now let's take a look at 2X Li-ion cells. Hot off the charger, these can give a voltage of 4.2V per cell, this equals 8.4V for 2 series connected cells.
Now compare the 6.6 to 8.4 volts and you'll see: fresh Li-ion cells have a LOT higher voltage. Although the voltage will go down rapidly to around 7.6V or less, it is still too much for the P91. It will either instaflash or have its life severely reduced.
The P90 lamp however, draws only around 1.15 Amps and under this load, a primary CR123A cell will sag to around 2.5V per cell. This equals 7.5V for the P90 with three cells in series. Note that THIS is nearly perfectly compatible with the voltage of 2X L-ion cells (around 7.4 to 7.6V). The short-duration higher voltage is no problem for the P90.
So, if you would like to have a GOOD rechargeable option for your C3 or 9P, forget about the P91, take the P90 instead, and buy yourself some good protected 17500 Li-ion cells. (AW black label).
Note: TWO 17500 cells have the same length as THREE CR123A cells in series. Two of these 17500s are an instant replacement for three CR123A batteries, as long as you use the P90
I ran this configuration from the start, about two years ago. My C3 is still on its first P90.... so yes, it's a durable option (I use this light a lot!)
EDIT: the P90 is also perfectly compatible with 2X 18650. Runtime with 2X AW 18650-26 will be over 2 hours!
Timmo.
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tobrien
Flashlight Enthusiast
I know it's still not recommended but what kind of runtime might we be looking at (assuming we don't insta-flash the bulb) with two 3400 mAh 18650s on a P91?
LEDAdd1ct
Flashlight Enthusiast
3400mAh capacity / 2700mAh draw = 1.259 hours runtime
1.259 hours * 60 minutes = 75.54 minutes
tobrien
Flashlight Enthusiast
ahhh there we go. I totally neglected to think about the math lol. thank you sir!
LEDAdd1ct
Flashlight Enthusiast
You are welcome.
I always think about pizza:
Eight slices in a pie.
Four people.
Divide what you have by your "draw," in this case, four people:
8 / 4 = 2 slices per person
When I first typed my post I accidentally reversed the division problem.
Thinking of pizza made me remember it is (usually) a poor idea to begin splitting people and assigning them to the pizza
rather than the other way around.
-----------------------------------------------------------------------------------------------------------------
7.50 years ago, this post was made:
In that post, it is implied that 2x18650 is a "safe" way to run a P91.
However, that post is 7.5 years old, and the current available from your "average" high capacity, high quality, Panasonic 18650 cell is a lot more than "way back when."
If we scroll down the page a bit, we see this:
What this tells us is that while the LiCo 18650 cells available "way back when" this guide was first created suffered too much voltage sag, the IMR LiMn version did not. Hmm...an AW 18650 IMR with LiMn chemistry was pretty much the only IMR cell in town 7.5 years ago. The latest iteration is stated to be able to provide up to 20 amps. While your modern 3400mAh Panasonic cell in October 2014 won't go quite that high, let's check it's specs.
Panasonic's data sheet says it can handle 2C (6.8A) continuously but
Pulse current (5–6 sec.): 12A(!)
So, what does this mean?
It means that when the (truly terrific) incandescent guide and compatibility chart was last updated
your run of the mill 18650 would likely sag too much to be able to instaflash a P91.
Battery technology has moved forward, and an 18650 capable of sustaining 6.8 amps continuous draw is not going to sag as much, as fast, and will pose a greater threat to the bulb.
Hope this helps!
I always think about pizza:
Eight slices in a pie.
Four people.
Divide what you have by your "draw," in this case, four people:
8 / 4 = 2 slices per person
When I first typed my post I accidentally reversed the division problem.
Thinking of pizza made me remember it is (usually) a poor idea to begin splitting people and assigning them to the pizza
rather than the other way around.
-----------------------------------------------------------------------------------------------------------------
7.50 years ago, this post was made:
In that post, it is implied that 2x18650 is a "safe" way to run a P91.
However, that post is 7.5 years old, and the current available from your "average" high capacity, high quality, Panasonic 18650 cell is a lot more than "way back when."
If we scroll down the page a bit, we see this:
What this tells us is that while the LiCo 18650 cells available "way back when" this guide was first created suffered too much voltage sag, the IMR LiMn version did not. Hmm...an AW 18650 IMR with LiMn chemistry was pretty much the only IMR cell in town 7.5 years ago. The latest iteration is stated to be able to provide up to 20 amps. While your modern 3400mAh Panasonic cell in October 2014 won't go quite that high, let's check it's specs.
Panasonic's data sheet says it can handle 2C (6.8A) continuously but
Pulse current (5–6 sec.): 12A(!)
So, what does this mean?
It means that when the (truly terrific) incandescent guide and compatibility chart was last updated
your run of the mill 18650 would likely sag too much to be able to instaflash a P91.
Battery technology has moved forward, and an 18650 capable of sustaining 6.8 amps continuous draw is not going to sag as much, as fast, and will pose a greater threat to the bulb.
Hope this helps!
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leukos
Flashlight Enthusiast
If you want to use 2x 18650 with a lamp why not just use the Lumens Factory EO 9 which is spec'd for li-ions?
cenz
Enlightened
Even with a pair of IMR18650s, P91 is yellowish than LF-IMR9 and EO9
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I use P91 with 2 x IMR16340 - BUT I also use AW's switch with soft start & 3 levels.
