Fenix P3D and Lithium-ion Batteries

I sent the following email to [email protected] and got the response included farther below.
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EMAIL TO FENIX

I understand that the P3D is designed for two 3.0-volt primary batteries and is not warranted to work with rechargeables.
Will typical 3.0 volt RCR123's and 3.6/3.7 volt protected RCR123's fit? Do you know the tube's inside diameter?

Will a typical (3.7v) R17670 battery fit? Will it operate normally? Normal operation means that I could use all the normal light-intensity options (low, medium, high, turbo) and operate the flashlight until the 17670 battery spends a normal cycle of energy.

What are the min./max. voltage thresholds of the regulator?

Can the IC handle up to 8.4v? Does the IC have low-voltage shut off?

What is the current draw in Turbo mode?

RESPONSE FROM FENIX

The tube's inside diameter is 16.8mm. And its voltage is from 6.0-8.4V, when the voltage is low, the light will warning.
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Please help me interpret the response from Fenix. Would I be correct to believe that using two standard 3.6v RCR123's would work without harming the LED? How about other rechargeable options?

I understand that much of what could be said would be speculation until the P3D's ship around 4/20/07. However, Fenix did give some new data that is not posted by their distributors.

I could be wrong, but it sounds like this thing will approximate what happens when you put a 17670 into a Gladius. You get a "low battery" blink occasionally which may irritate some but doesn't bother me much. Other than that, it should work fairly well.

The reason for this speculation is how closely the L2D I got last week resembles a Gladius. Compared side-by-side they have the same beam shape & spill and both strobe at the same speed. The main difference is the L2D is noticeably brighter (in turbo and strobe). Possibly they both handle batteries the same way.

What I am wondering is whether the "low battery" aspect will interfere with getting 160 lumens out of a 17670 in turbo. If it does, there won't be much rationale for me to upgrade because I'm inclined toward rechargeables. Can't stand to start out the day with partially used primaries.

cliff said:

What I am wondering is whether the "low battery" aspect will interfere with getting 160 lumens out of a 17670 in turbo.

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If the light is set up for use with 2 primarys for a total of 6.0v, won't the 17670's 3.7 volts make for significantly less than 160 lumens?

Their response of the input voltage is 6-8.4v means it can take two primary lithium batteries, or two rechargeables (very nice). Putting one rechargeable will trigger the low voltage warning flash, which lets you know the light is okay, but the input voltage is unacceptably low for the light to function----so no, a 17670 or any one cell will not work.

Their response to the voltage input indicates rechargeables will work assuming they are slimmer than 16.8mm, since some protected cells have a lump on the side where the wire runs.

Their response of the input voltage is 6-8.4v means it can take two primary lithium batteries, or two rechargeables (very nice). Putting one rechargeable will trigger the low voltage warning flash, which lets you know the light is okay, but the input voltage is unacceptably low for the light to function----so no, a 17670 or any one cell will not work.

Their response to the voltage input indicates rechargeables will work assuming they are slimmer than 16.8mm, since some protected cells have a lump on the side where the wire runs.

Will the light seriously not work with less than 6v? That doesn't make much sense. Not only would that eliminate any possibility of using a 17670, but it won't come close to draining primaries either (not that you really want to drain two cells at the same time).

Martini said:

That doesn't make much sense.

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That's what I'm thinking. The Gladius is supposed to run on two 3-volt lithiums also, and a 17670 doesn't put out anywhere near 6 volts - yet the light works well on one if you don't mind the occasional low-battery blink. The fact that this L3D has a low-battery blink of some type makes me suspect it is a very similar setup, but I am just an unwashed, ignorant buyer of too many flashlights - not an engineer.

mc3jp2 said:

RESPONSE FROM FENIX

The tube's inside diameter is 16.8mm. And its voltage is from 6.0-8.4V, when the voltage is low, the light will warning.
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Please help me interpret the response from Fenix. Would I be correct to believe that using two standard 3.6v RCR123's would work without harming the LED?

Click to expand...

I am suspicious that the response comes from their marketing people rather than engineering. Reason I say this is really just "reading between the lines" on their response:

8.4V happens to be pretty close to the open-circuit voltage of two fully-charged Li-ion cells in series

6.0V happens to be pretty close to the open-circuit voltage of two brand-new high-quality primary CR123A in series

The Fenix response implies that you'll get some sort of warning when the voltage on the circuit falls below 6.0 volts. Implies, but, importantly, it does not actually say that. Realistically, it can't be true, presuming the P3D runs just fine on 2xCR123A. Even fresh, they do not produce 6.0 volts under load.

Guessing now, I'd say it's got a buck circuit not buck/boost. It'll most likely run fine down to a few tenths above Vf (say roughly 4.0V input) at which point, as they tell us, it's going to give some sort of signal. Note, this equates to an average of 2.0V per Li-ion rechargeable, which happens to be a very good time to be pulling them out and recharging them. Therefore, it's not going to like a single-cell Li-ion such as 18650, 17670.

soffiler said:

I am suspicious that the response comes from their marketing people rather than engineering....

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The response from Fenix was given by:

Elly
Fenix service team

Apparently, 2 x 3.6v RCR123A cells will run on the P3D without harming the LED.

Does the fact that the P3D gives a low battery warning mean that it is safe to run unprotected RCR123A's? Does a low battery warning mean that the P3D has some kind of low-voltage shut off, making the use of unprotected cells safe?

Would there likely be a problem making most protected RCR123A's fit into a 16.8mm tube?

Is there any reason to consider using 3.0v RCR123A's instead of 3.6v?

Dunno the answers to your questions, but I'll just comment that I'm not a big fan of unprotected Li-ion, especially when you are talking about running two of them in series. In that case, all the P3D sees is the total voltage, and using 4.0V as an example, there's no way to tell whether it's 2.0V from each cell, or 0.1V from one and 3.9V from the other. In other words, too much danger of excessive discharge of one of the cells.

EDIT: my numbers above present just a casual example, and that is a mistake on my part. One should NOT take unprotected Li-ion casually! Furtheremore, the danger zone for excess discharge is 2.5 volts per cell, so two perfectly matched cells will cross into their danger zone at 5 volts where the P3D is running happily and provides no indication of any sort of problem whatsoever. Furthermore, nothing's perfect in the real world, so the problems will actually kick in at an even higher voltage, even further away from the P3D's low-voltage indication.

UNPROTECTED Li-ION IS A BAD IDEA.

Fenix now has P3D information on there site. I thought this was interesting:Uses two 3V CR123A batteries (3.6V~8.4V).
http://www.fenixlight.com/flashlight/fenixp3d.htm

If the threading were compatible, I imagine it would be possible to use a R17670 with a P2D head (which Fenix's website suggests is actually the same as the LxD head) on a P3D body. The input voltage would then be correct, but of course you wouldn't get the P3D's 160 lumens.

Given that the manufacturer's website (fenixlight.com) now states, "Uses two 3V CR123A batteries (3.6*V~8.4V)", are we being told what the "min./max. voltage thresholds of the regulator" is?
*[Edit note, 4/11/07: The manufacturer slightly changed the specification to read, "Uses two 3V CR123A batteries (3.7V~8.4V)".]

Thus each cell on average would have a min./max. range of 1/2 x (3.6V~8.4V) = (1.8~4.2V), which would indicate 1.8v min. (discharge) and 4.2v max. (peak charge).

If a peak value of 4.2v is true, then the manufacturer is implying that standard 3.6v RCR123A batteries fall within their specifications for the P3D. Is my interpretation and conclusion valid?

mc3jp2 said:

Given that the manufacturer's website (fenixlight.com) now states, "Uses two 3V CR123A batteries (3.6V~8.4V)", are we being told what the "min./max. voltage thresholds of the regulator" is?

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I can't speak for Fenix, but personally, yes, that's what I would conclude.

Thus each cell on average would have a min./max. range of 1/2 x (3.6V~8.4V) = (1.8~4.2V), which would indicate 1.8v min. (discharge) and 4.2v max. (peak charge).

Click to expand...

Yes.

If a peak value of 4.2v is true, then the manufacturer is implying that standard 3.6v RCR123A batteries fall within their specifications for the P3D. Is my interpretaion and conclusion valid?

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Logically and arithmetically it all hangs together, yes.

I can't think of any reason why a Lithium primary would EVER have an output greater than 6.0v, so why would they even mention 8.4v unless the design allows for the use of 3.7v cells?

Now I am wondering what effect the use of 3.7v cells will have on the various output levels. When I use a 3.7 in my P1D CE, all levels are Max. Will the same thing happen with the P3D?

How much longer/wider are CR123A protected cells vs. unprotected? Think protected would fit in the P2D or PD3?

soffiler said:

...I'm not a big fan of unprotected Li-ion, especially when you are talking about running two of them in series ... too much danger of excessive discharge of one of the cells.

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Could the danger of excessive discharge of an unprotected cell be sufficiently offset by load-testing each cell after charging to verify that they are reasonably balanced in voltage before putting them to use? After verification and insertion, if one cell indeed dropped to 0.1v, would it have behaved the same way (presented the same sort of danger) whether or not it was a protected cell?

If a cell does fail during usage, I suppose a protected cell would cut off all incoming and outgoing voltage whereas an unprotected cell could then begin receiving a dangerious charge-current from the healthy cell.

Is anyone using unprotected cells in series? If so, what safety precautions do you take?

mc3jp2 said:

Could the danger of excessive discharge of an unprotected cell be sufficiently offset by load-testing each cell after charging to verify that they are reasonably balanced in voltage before putting them to use? After verification and insertion, if one cell indeed dropped to 0.1v, would it have behaved the same way (presented the same sort of danger) whether or not it was a protected cell?

If a cell does fail during usage, I suppose a protected cell would cut off all incoming and outgoing voltage whereas an unprotected cell could then begin receiving a dangerious charge-current from the healthy cell.

Is anyone using unprotected cells in series? If so, what safety precautions do you take?

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Any and all unprotected Li-ion cells are a bad idea in my opinion, which is primarily based on a LOT of information available right here on CPF and elsewhere all over the 'Net. And it goes from bad to worse very quickly when you start talking about unprotected cells in series. DON'T DO IT.

Here's a place to start your research:

https://www.candlepowerforums.com/threads/106242

And please make particular note of this post:

https://www.candlepowerforums.com/posts/1257910&postcount=12

Thus each cell on average would have a min./max. range of 1/2 x (3.6V~8.4V) = (1.8~4.2V), which would indicate 1.8v min. (discharge) and 4.2v max. (peak charge).

Click to expand...

am i right that i can't run the P3D head with a 2AA-tube / NiMh?
only 2x14500 will work in a 2AA??

Everybody who is following this thread, please note my edit in post #10!