Aluminum contacts as a cause of flashlight problems

I see a lot of posts about cleaning up threads and applying chemicals to fix flickering and other contact problems. I believe that this is largely due to the use of aluminum as part of the electrical connection. It may be good to use aluminum as a case but it is not a good idea to use it to connect the bottom of the battery to the lamp as many flashlights do.

Some of you probably remember that years ago they started wiring houses with aluminum wire. After a few fires there was a backlash and copper was again king.

The problem is that aluminum forms a non-conductive oxide coating resulting in a poor electrical connection. In a house this builds up heat while in a flashlight you have to work the threads back and forth to get the light to come on. My understanding is that titanium also has this problem.

If there is enough voltage it can punch through the layer but the few volts from a battery has trouble. Electrical switches that are rated for low voltage have gold plated contacts because of this problem.

I wish the people designing flashlights would recognize this and figure out an alternative.

SureFire have. Check out their A2/L1/L2/U2/K2/UA2/UB2

BTW, Gold-plated contacts are rarely beneficial in the context of flashlights. This is especially the case in terms of durability where the contacts are subject to rotational moment whilst contacting such as the turning of a TailCap etc or successive batteries being rotated against a gold-plated spring contact. In fact it's almost a cheap surface finish compared to finding one that will actually work.

Size15's said:

SureFire have. Check out their A2/L1/L2/U2/K2/UA2/UB2

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Do you mean chemkote?

Crenshaw

I don't know about other models, but my SF A2 has a contact ring made of steel or something similar, which makes the contact to the tailcap.

It's not steel or aluminium - its a coated metal alloy (I'm not sure I can say what it's made of) that has, I'm led to believe a superior contact performance than, well, pretty much everything else (including Gold) in its application. The two-stage switch is very sensitive to resistance and SureFire have gone to great lengths to reduce resistance not only to begin with but also over time through use.

You can see it here on the U2:


And here on the proto-type UA2:

I imagine that twisty type lights which don't conduct electricity through the threads (end contact, spring loaded lights like the Civictor, Fenix L0x, and new model Gerber Infinities) might be a little more reliable because they provide a wiping action when the aluminum end of the body contacts whatever it hits.

I do clean off body and head/tail contact surfaces on my typical lights once in a while with a dry Q tip. On some, I've actually wedged in something like a ring of stranded copper wire between the body and head which seems to maintain good contact over fairly long times.

It is certainly bad form to rely on contact between threads rather than a pair of contact surfaces. I'm pretty sure it is done though.

Wolf-Eyes lights have brass contacts.

Size15's said:

It is certainly bad form to rely on contact between threads rather than a pair of contact surfaces. I'm pretty it is done though.

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Many lights do this. Pretty much all "crush your battery" type twisties (Arc AAA, Arc LS, CMG Infinities, Peaks, Jetbeam CLEs, and many lights where the threads aren't anodized) rely on the threads to provide electrical continuity. Workable, but require some maintenance and not as good as end contacts...

Size15's said:

It's not steel or aluminium - its a coated metal alloy (I'm not sure I can say what it's made of)

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Oooooo, aren't we being coy? Would you happen to be referring to the so secret - I would have to kill you if I told you - beryllium copper?

Great for contacts, not so good for your lungs. The Surgeon General warns that inhaling your Surefire could damage your health.

Size15's said:

It's not steel or aluminium - its a coated metal alloy (I'm not sure I can say what it's made of) that has, I'm led to believe a superior contact performance than, well, pretty much everything else (including Gold) in its application.

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I find that EXTREMELY difficult to believe.

Cheapskate said:

Oooooo, aren't we being coy? Would you happen to be referring to the so secret - I would have to kill you if I told you - beryllium copper?

Great for contacts, not so good for your lungs. The Surgeon General warns that inhaling your Surefire could damage your health.

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I'm not certain whether the details are already CPF knowledge so if you know it to be 'beryllium copper' then so be it.

LukeA,
As I understand it the quality and durability of a contact system in use and through use are more important than an ideal 'just manufactured' system for which abrasion, environmental (etc) and wear is not taken into account.

Size15's said:

I'm not certain whether the details are already CPF knowledge so if you know it to be 'beryllium copper' then so be it.

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"SureFire momentary switches are rubber - sealed beryllium copper pads"

http://www.surefire.com/maxexp/main/co_disp/displ/pgrfnbr/554/sesent/00

"SureFire engineers incorporated a relatively long "tape switch," a pressure-sensitive rubber sealed pad, that contains two strips of beryllium cooper contacts."

http://www.surefire.com/maxexp/main/co_disp/displ/pgrfnbr/563/sesent/00

I could be entirely wrong of course.

You're making the assumption that the material used in the tape-pressure switches is the same as is used by the contact-ring of the A2/L1/L2/U2/K2 etc.

Cheapskate said:

Oooooo, aren't we being coy? Would you happen to be referring to the so secret - I would have to kill you if I told you - beryllium copper?

Great for contacts, not so good for your lungs. The Surgeon General warns that inhaling your Surefire could damage your health.

Click to expand...

:laughing:Funny, I'm trying to picture that. Obviously, in this application, a beryllium alloy would pose essentially no health risk.

LukeA said:

I find that EXTREMELY difficult to believe.

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What's so difficult to believe? Gold has very poor wear resistance. I believe the ideal material for this application would be something relatively HARD (ie, wear resistant) with reasonably good electrical conductivity.

Cool thread - this is an interesting engineering challenge I had never really thought much about.

Size15's said:

You're making the assumption that the material used in the tape-pressure switches is the same as is used by the contact-ring of the A2/L1/L2/U2/K2 etc.

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Certainement!

I have an admittedly bad habit of extrapolating, given half a chance.

It could be Osmium or Platinum, but the slight brassy colour makes Beryllium copper a reasonable guess.

"Appearance and Odor: Solid, odorless, brassy yellow ..."

I'm not saying you're wrong to assume - like I said I'm not aware of the details of the material and finish being mentioned on CPF.

Ledlenser uses goldplated contacts in most of their lights.

Gold is supposed to be the most conductive material around, I doubt that surefire has invented anything better...

kts said:

Gold is supposed to be the most conductive material around, I doubt that surefire has invented anything better...

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I'm not saying they have 'invented' a more conductive material than Gold.
I'm saying that they're using a better electrical contact material than Gold for use in most flashlight applications.
Gold is very soft and easily worn away. It is rather poor choice of contact surface when the contact surfaces are moving/rotating against each other in use.

Agree with Al. Abrasion is the problem of gold contacts.

Here's an example ... a Pentagonlight that was just being used in a passaround:



... and the gold contacts already disintegrated. Useless.

bernie