LOD-CE Q4 Twist Contact Advice

Ist is just my LOD-CE Q4 or does this twistie require a strong twist to get the conatct engaged and the light flowing? The torque required is more than that of my P1D Q5 but I'm attributing to this to the smaller thinner threads of the LOD. Any advice? I just want to make sure that this is standard on this light. It is very bright though for a keychain light. I am quite impressed.

Mine takes a two handed twist or I end up with no light or in low.

Sucker is BRIGHT in Hi ain't it?

Ample light on all levels but super bright on high, I agree PJS. I know it runs only 1.5 on high but it lights the whole room! At low, it's plenty of light for emergencies at 9.5 hours.

I put a little precision lube on the o-ring and a tad on the threads and now get a very smoothe turn.

seanflash said:

Ist is just my LOD-CE Q4...

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I had the opposite issue with a red LOD Q4 and a natural P1D Q5. The LOD's twist action was smooth. The P1D's wasn't but only at the very last bit of tightening, requiring two handed operation. Upon closer inspection, there was some flash (rough jagged finish) on the threads of the P1D body. A couple of mins with a needle file made the threads smooth and much better .
I suppose I could have exchanged it but, for such a small issue which was easily rectified, I didn't .

Apply Balistol to the threads and then put a wrap of Tommy tape on the head.

seanflash said:

Ample light on all levels but super bright on high, I agree PJS. I know it runs only 1.5 on high but it lights the whole room! At low, it's plenty of light for emergencies at 9.5 hours.

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The L0D is one bright little light. The L0D and my old v1.2 Jetbeam C-LE AA light are two of my favorites.

My L0D was also a little twitchy about turning on, but after proper contact cleaning and thread lubrication, it now gives perfectly smooth one handed operation.

The first thing anyone with a LOD needs to understand is exactly how the contacts work in this light. It's important to note some of the differences in these twisty lights like the C-LE and L0D, and look at the best way to get the best results from the L0D.

I have seen many posts from folks who were looking for 'conductive lubricants' , or asking the best way to 'clean the threads', etc.

These questions indicate a fundamental misunderstanding about how the L0D's twist switch works.

It's easy to see how this confusion comes about, because there are lights out there that use a type of twisty switch that does require that the threads conduct electricity; however, this is NOT the type of switching used in the L0D. (the most common example of a light using the conductive-threads arrangement is the Jetbeam C-LE v1.2)

Unlike the Jetbeam C-LE, the Fenix L0D has completely non-conductive anodized threads (which are more durable mechanically).

To make electrical contact, the L0D relies on a conductive ring of bare metal at the very end of the battery tube to make contact with a similar ring shaped metal pattern on the bottom of the light-engine circuit board.

Because of the spring at the bottom of the battery tube, the battery is pushed upwards, and the plus side of the battery is always in contact with the center contact dot on the bottom of the light engine. Switching occurs when the battery tube is screwed down so it's end contacts the outer ring on the bottom of the light engine PCB.

With this switching arrangement, conductive threads are not needed, and would provide NO advantage, so you NEVER want to try to clean the anodized coating off of the threads of the L0D. Doing so will simply cause the threads to wear out quickly, and it will do NOTHING to help the electrical contact.


Cleaning the L0D's contacts is quite simple; there are just THREE points of electrical contact -

- The top (plus side) of the battery contacts a small round spot on the bottom of the light engine driver PCB.

- The twisty switch contacts between the ring of bare metal at the top end of the battery tube and the PCB foil metal ring on the underside of the light engine driver PCB (this is the silver ring of metal which surrounds the small circular dot that contacts the plus side of the battery).

- The bottom (minus side) of the battery contacts a spring at the bottom of the battery tube (and this spring must also have good contact with the aluminum battery tube).


So here's how to go about contact cleaning in an L0D -

- Use a Q-Tip cotton swab that has been very slightly dampened with alcohol to clean the positive dot and minus ring contacts on the underside of the light engine PCB.

- To clean the ring of bare metal at the end of the battery tube, first buff it with a paper towel lightly dampened with alcohol, then lightly buff the end of the battery tube against a rough paper surface or very fine grit sandpaper to remove any oxidation. For the contact to work properly, the end of the tube must remain square and true. To insure that the battery tube remains properly square and true, I hold the battery tube vertically, contact end down, nice and flat and square against some 1000 grit sandpaper (which is laid flat on a table top), and give the battery tube a couple of nice smooth twists.

- If needed, you can also use a 1/4 inch blunt wooden dowel to depress and buff the bottom spring contact. Depressing the bottom spring several times with moderate pressure with the dowel, using a slight side to side motion, will clean the top surface of the spring (which is in contact with the negative side of the AAA cell), and will also insure that the bottom side of the spring breaks through any oxidation that has formed and makes a clean metal-to-metal bond to the battery tube.

:thumbsup: Luminescent

cv3po said:

EDIT: won't this ring of foil (or whatever) for the neg contact in the head wear out faster from the twisting than if it DID contact through the threads?

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If the contact surface at the top of the battery tube is clean, as well true and square to the axis of rotation, the contact area will be fairly broad, and the battery tube will not turn very far once the surfaces meet (which should minimize wear).

I was concerned about this problem with my Rebel 100 moded Ultrafire B3. The B3 uses the same twisty arrangement, but it's PCB looked like the foil was a bit flimsier than the L0D, so I ran my soldering iron around the rim of the ring contact in one nice even circular pass, and built up a thin even layer of solder around the contact ring. The solder I used is a nice eutectic alloy of 62% Tin, 36% Lead, 2% Silver, which not only melts about 5 degrees cooler than the standard 63% Tin, 37% Lead solder mix, but is also stronger due to the silver content.

This is a big hassle though, because you have to be pretty handy with a soldering iron to pull this off without shorting something out by getting solder where it's not supposed to be. Fortunately, unlike the Ultrafire B3, the ring contact on my Fenix L0D looked pretty solid right out of the factory, so I didn't bother to try to coat it with any more solder, and so far it still looks almost new, even after several months.

I will confess that I did add a thin layer (about a half mm or so) of solder to the center contact dot on the underside of the L0D's driver though. The center contact is a LOT easier to solder, and I figured that the center dot sees a lot more friction.

If you turn the light a quarter turn every time you power cycle it from off to on, then the outer ring only contacts with modest pressure during the last few degrees of travel, but that center pin of the battery is pushing up hard against the center contact, under a strong spring load, during the whole 90 degree cycle.

Depending on the shape of the positive battery contact, the point of wear can be fairly small and concentrated, and I thought I was beginning to see some slight wear, so I figured 'better safe than sorry' and gave it a quick dab of solder.

Not something I would necessarily recommend to everyone though, because there are lot's of L0D's out there going strong after several years without this treatment, and it's not a good idea to risk it if your not real handy with a soldering iron.

Also, on another subject, I should have mentioned before that another thing that I have found to be a bit more critical for one-handed operation with the L0D than with some other lights, is the type of lubrication you use on the O-Ring.

The O-Rings Fenix uses on this light are really good at squeegeeing right trough most lubricants and creating O-Ring 'stiction' issues (creating a lot of turning resistance).

For example silicone grease, which might work ok with another light, is a HORRIBLE situation with the L0D. If anyone out there is using the wrong lubrication, then that alone would explain why you can't use your L0D one handed. With my Jetbeam C-LE, the tough issue was finding a grease that would minimize wear on the soft aluminum threads, but with the Fenix L0D-Q4, it was getting smooth operation and preventing the O-ring from binding.

I finally ended up using Locktite Krytox high performance lubricant grease on my L0D-Q4 to get past the O-Ring sticking issues. I'm not a big fan of Krytox overall, because this stuff is NOT what you want to use on lights with bare aluminum threads (because the PTFE particles will actually cause excessive wear), but on the HAIII anodized threads of my L0D, it seems to be working like a champ.

Krytox costs an arm and a leg though (about 45 bucks for 2oz tube!), so most folks will want to try something else like Nyogel 760G or simple lithium grease. For example, Mobil 1 car grease is a synthetic lithium grease which will work well on both bare aluminum threads, and anodized threads.

With Nyogel 760, Mobil-1 Grease, or simple Lithium Grease, there may be some slight 'stiction' as the O-Ring on the L0D first starts to turn, but once you get it moving, it turns quite easily, making for quite smooth one handed operation. (Some folks may even like the initial 'stiction' effect in the o-ring anyway, because it makes it very unlikely that the L0D will turn on accidentally in your pocket.)

Don't forget the battery itself, I always clean the battery's contacts and then don't touch them while installing it into the light.
In addition with twistie lights, I will lightly abrade the contacts on a primary battery and then clean them again.
I learned this when I bought a complete Peak Matterhorn and a spare pocket body. Later when I bought a second head to make a complete light, I had terrible contact issues and dim performance even after cleaning everything. When changing the alkaline battery in the first light that came already installed by Peak, I noticed they had abraded the contacts. I tried this with the battery I had installed in the second light and the difference was huge. It was finally working up to its potential with just an easy twist.
The Matterhorn works differently than the LOD and does use conductive threads, but any point of resistance you can remove will help, and battery contacts can already be oxidized when new out of the package.

Thanks for all of the great advice. I am glad to learn of the engineering and technical connections that make this light work. I will clean the contacts and threads as advised. Nyogel seems to be the favored lube. Right now, I only have lithium grease, so I'll use that in the meantime. Much appreciated.