AW IMR cells in a p2d

I own a fenix p2d and I use aw protected rcr123 cells. Would I be able to use unprotected IMR cells as well, or would the lack of protection possibly fry my p2d? What do yall think? should I take the risk?

the light will run direct drive with those cells, and as they have a much lower internal resistance compared to normal RCR123 cells the LED will see a lot of current if you use the IMR cells, probably being brighter but also very likely to overheat
so my advice is, better not try it, just use your 'normal' cells and be happy

kicken_bright said:

I own a fenix p2d and I use aw protected rcr123 cells. Would I be able to use unprotected IMR cells as well, or would the lack of protection possibly fry my p2d? What do yall think? should I take the risk?

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The IMR is 3.7 volts similar to AW protected RCR123. In my opinion, using it should not fry your light but you'll lose most of your modes. However, that being said, Fenix does recommend using Lithium Primaries.

Have you tried AW's LifePo4? I have been using LiFePo4 for over a year in my P1D Q5 and love it. Slightly less capacity than the IMR (LiFePo4 rated at 500Mah @ 3.2V ) but you get all your modes and probably safer with the voltage being very close to a Lithium primary.

kicken_bright said:

Would I be able to use unprotected IMR cells as well, or would the lack of protection possibly fry my p2d?

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The protective circuit in a cell is to protect cell from over discharge. It has nothing to do with protecting the light.

Have you tried AW's LifePo4? I have been using LiFePo4 for over a year in my P1D Q5 and love it. Slightly less capacity than the IMR (LiFePo4 rated at 500Mah @ 3.2V ) but you get all your modes and probably safer with the voltage being very close to a Lithium primary.

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I agree. I've used a LifePo4 in a L1T for close to a year now with no problems whatsoever. Plus the low and high modes work just fine.

Helmut.G,

IIRC the only conceivable difference between the RCR and IMR is that the IMR allows a greater current output than RCR with the sacrifice of capacity...

Assuming your light is regulated [in the case of the P2D, it is] and not direct drive, theres going to be a middle man between your LED and the battery. The driver should only draw the current it needed for operation and not more, so chances are you are only going to notice a shorter runtime.

Under the same working voltage hooking up a 2AH eneloop battery pack up to a 80mm computer fan versus hooking the fan up to a 100AH lead acid battery pack should yoeld no difference in cfm but note the current output capability of the lead acid versus the eneloops.

now if your light is DD that may be a whole other issue

hmm... correct me if i'm wrong... but i thought the IMR cells are just a lil less capacity as the AW protected ones... BUT... at continuous high current draws, will actually last longer than the protected higher capacity ones...

also... at the low side of the current draw... you actually get even less runtime as IMR's aren't geared towards low current draw applications...

KraZy

hehe, there seems to be quite a lot of confusion about IMR cells.

IMR in your P2D will perform identically to an RCR except with less runtime (i.e, you'll still loose lower modes for the first few minutes). Also, it's a safe chemistry so can't vent with flame. At high current draws, the useful capacity of a standard li-ion is decreased, so despite the lower nominal capacity of the IMR, it can last longer as it delivers its stored power more efficiently due to lower internal resistance. At relatively low currents (i.e, P2D), this doesn't come into effect, so the higher nominal capacity of the conventional li-ion results in longer runtimes.

Like all cells, IMR will give more capacity at lower discharge currents, but as soon as you increase the current, the IMR is much more effective at delivering the high currents than the "normal" cell.

krazy89 said:

hmm... correct me if i'm wrong... but i thought the IMR cells are just a lil less capacity as the AW protected ones...

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:huh2:
550mah from 750mah, thats a ~27% reduction in capacity!
just a lil ain't gonna cut it

dunno... I'm not sure about voltage sag concerning lithiums, I only know that they do not directly reflect the same characteristics as would NiMH or Alkalines

Illum_the_nation said:

Assuming your light is regulated [in the case of the P2D, it is] and not direct drive, theres going to be a middle man between your LED and the battery. The driver should only draw the current it needed for operation and not more, so chances are you are only going to notice a shorter runtime.
now if your light is DD that may be a whole other issue

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The P2D is known to lose the current-regulated low modes at 3,7 V (all modes will be the same) so I assume it's DD with IMR123 cells as well as regular RCR123
am I wrong?

that I don't know oo:

IIRC AW RCR123As can dump ~2.5C before the safety kicks in. 2.5C = 2.5x750mah = 1875ma or 1.875 amps...if the P2D works on RCR123As I don't think the LED will see that sort of current to tell you the truth

my point is that in DD the LED will see more current if you use IMR cells, and the heat might become a problem

krazy89 said:

hmm... correct me if i'm wrong... but i thought the IMR cells are just a lil less capacity as the AW protected ones... BUT... at continuous high current draws, will actually last longer than the protected higher capacity ones...

also... at the low side of the current draw... you actually get even less runtime as IMR's aren't geared towards low current draw applications...

KraZy

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I am aware that IMR cells have less capacity than protected AW cells; however, I am about to purchase some IMR cells for a halogen set-up, and I was wondering if they could also be used in my p2d as well.

I am also aware that my p2d runs on direct drive with rechargeables. Without the protection of the p2d circuit, I am wondering if these high amp IMR cells will push out more current than the regular AW's. Will an LED on direct drive pull enough current to fry itself?

Helmut.G said:

my point is that in DD the LED will see more current if you use IMR cells, and the heat might become a problem

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Kind of true, but I doubt it'll be problematic. The only thing you're changing is loosing an absolute max of 100 milli-ohms resistance..... in other words, think of having a Cv source at 4V DD'ing an LED, and adding in or removing a .1 ohm resistor... what's that going to do to the current? Not that much.... (IIRC, resistance of an LED ~ 4ohms at decent drive currents)

In other words, it'll be fine as long as you don't over-discharge the cells.