Quickly within my ownership of my P1, I found it to be unreliable, as others here at CPF have commented. It would flicker, go dim, turn off. After some failure analysis, it turns out there is a connection problem between the battery and pill.
When I unscrewed the pill from the P1, it turned freely. Once removed, I found lots of dark garbage in the threads, mostly on the brass pill. After cleaning and reassembling the pill tightly, it worked much better. But soon afterward, I found the pill loose again. It turns out that the heat produced by using the P1 loosened the pill. After tightening the pill again while the device was hot, it worked better for a longer period of time.
Side note: I made more of an effort to clean the threads near the reflector and got some isopropyl alcohol in the reflector area. Don't let this happen, it destroys the mirror finish of the NON SERVICEABLE reflector. For the same reason, you never want to break your P1 glass, it cannot be serviced. I rendered my P1 effectively useless by this mistake.
The Fenix P1 conducts electricity from the negative battery terminal, through the aluminum threads of the tail, into the aluminum threads of the head. I find no problem with this, aluminum-to-aluminum has a record of working well because the twisting action continually cleans the oxides from the surface.
The electricity flows through the solid aluminum head, to the aluminum threads on the inside of the head that engage the brass pill (my nickname for the round assembly of the emitter and driver circuit).
I propose this screw-into-aluminum brass pill is an extremely poor contact system. As a side note, for the same reasons this interface is also a poor conductor of heat.
For a good electrical contact system between separate physical bodies, you need (1) clean, conductive metal surfaces; and (2) a force to push those surfaces together to sustain contact on a microscopic level.
Between the P1 pill and aluminum head, there are two dissimilar metals of two large bodies. They have different coefficients of thermal expansion, and expand/contract at different rates. This can loosen the threads. There is no crimp action to create an air-tight contact interface or a constant load on the contact faces. Insulating oxides form on both raw threads, there is no noble metals plated on the threads at all. This build up of oxidation/tarnish on the insulating surface contamination may possibly made worse by vapors exhausted by the battery. (Galvanic corrosion could be a small factor too, but dissimilar metals are used in flashlights all the time without issue.)
There is no "preload" on the screws faces, and therefore no friction to hold the pill from turning loose. When the pill is tightened, nothing physically stretches. Normally, when you use a machine screw it stays tight because the screw stretches a very small amount axially. But in this case, there are two big wads of material, neither is thin and long, neither is capable of sustaining a preload on the screws. 0 preload, 0 friction to keep the threads from turning. And since I found the pill loosens under temperature (I believe aluminum expands more than brass), you probably unscrew the pill a little when you turn the device off.
Now, when the P1 is new, the threads are probably relatively clean and the pill may be relatively tight. The force from the battery pushing the pill is probably enough to overcome a little bit of oxide/tarnish on the aluminum and brass threads. But over time, more tightening force will be required until it's never enough.
I noticed there is a very small flange on the brass, which has the potential for causing interference if the pill is highly torqued into the aluminum threads. Either Fenix is not tightening the pill enough to cause a permanent interference fit, or the design does not provide enough intereference to begin with. You and I probably don't have the right tool to tighten the pill permanently into the aluminum threads.
For the same reasons the pill does not conduct electricity from the aluminum threads, the heat from the pill is not being "sinked" into the aluminum threads very efficiently. Conduction is the primary means of effectively removing heat inside a sealed object, but here contact is barely present. Therefore radiation is the primary means of heat transfer within the device, and radiation requires a much higher temperature difference to transfer heat (dT^4 instead of dT).
Let me begin by saying I really like Fenix torches. I already own a P1, and have a P1D-CE on order. I hope the information below helps them improve.
I work as a Development Engineer in the Electronics Interconnect field. I don't know it all, but I consider my opinion worth considering. There are a lot of similar experts here, I'd like to hear if you agree or disagree. Thanks for your time!
When I unscrewed the pill from the P1, it turned freely. Once removed, I found lots of dark garbage in the threads, mostly on the brass pill. After cleaning and reassembling the pill tightly, it worked much better. But soon afterward, I found the pill loose again. It turns out that the heat produced by using the P1 loosened the pill. After tightening the pill again while the device was hot, it worked better for a longer period of time.
Side note: I made more of an effort to clean the threads near the reflector and got some isopropyl alcohol in the reflector area. Don't let this happen, it destroys the mirror finish of the NON SERVICEABLE reflector. For the same reason, you never want to break your P1 glass, it cannot be serviced. I rendered my P1 effectively useless by this mistake.
The Fenix P1 conducts electricity from the negative battery terminal, through the aluminum threads of the tail, into the aluminum threads of the head. I find no problem with this, aluminum-to-aluminum has a record of working well because the twisting action continually cleans the oxides from the surface.
The electricity flows through the solid aluminum head, to the aluminum threads on the inside of the head that engage the brass pill (my nickname for the round assembly of the emitter and driver circuit).
I propose this screw-into-aluminum brass pill is an extremely poor contact system. As a side note, for the same reasons this interface is also a poor conductor of heat.
For a good electrical contact system between separate physical bodies, you need (1) clean, conductive metal surfaces; and (2) a force to push those surfaces together to sustain contact on a microscopic level.
Between the P1 pill and aluminum head, there are two dissimilar metals of two large bodies. They have different coefficients of thermal expansion, and expand/contract at different rates. This can loosen the threads. There is no crimp action to create an air-tight contact interface or a constant load on the contact faces. Insulating oxides form on both raw threads, there is no noble metals plated on the threads at all. This build up of oxidation/tarnish on the insulating surface contamination may possibly made worse by vapors exhausted by the battery. (Galvanic corrosion could be a small factor too, but dissimilar metals are used in flashlights all the time without issue.)
There is no "preload" on the screws faces, and therefore no friction to hold the pill from turning loose. When the pill is tightened, nothing physically stretches. Normally, when you use a machine screw it stays tight because the screw stretches a very small amount axially. But in this case, there are two big wads of material, neither is thin and long, neither is capable of sustaining a preload on the screws. 0 preload, 0 friction to keep the threads from turning. And since I found the pill loosens under temperature (I believe aluminum expands more than brass), you probably unscrew the pill a little when you turn the device off.
Now, when the P1 is new, the threads are probably relatively clean and the pill may be relatively tight. The force from the battery pushing the pill is probably enough to overcome a little bit of oxide/tarnish on the aluminum and brass threads. But over time, more tightening force will be required until it's never enough.
I noticed there is a very small flange on the brass, which has the potential for causing interference if the pill is highly torqued into the aluminum threads. Either Fenix is not tightening the pill enough to cause a permanent interference fit, or the design does not provide enough intereference to begin with. You and I probably don't have the right tool to tighten the pill permanently into the aluminum threads.
For the same reasons the pill does not conduct electricity from the aluminum threads, the heat from the pill is not being "sinked" into the aluminum threads very efficiently. Conduction is the primary means of effectively removing heat inside a sealed object, but here contact is barely present. Therefore radiation is the primary means of heat transfer within the device, and radiation requires a much higher temperature difference to transfer heat (dT^4 instead of dT).
Let me begin by saying I really like Fenix torches. I already own a P1, and have a P1D-CE on order. I hope the information below helps them improve.
I work as a Development Engineer in the Electronics Interconnect field. I don't know it all, but I consider my opinion worth considering. There are a lot of similar experts here, I'd like to hear if you agree or disagree. Thanks for your time!
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