Observation on 2 basic twisty contact designs

LED Flashlights – General Info 1 x AAA Flashlights
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This is more a note about my observations on how an increasingly common design compares to the traditional contact behaviour. By which I refer to tradition as the design where there’s a spring ensuring battery is always in circuit and relying on break in path through the body for switching (driver neg contact is not bridged to sides and only complete circuit when lip of body tube touches contact plate). The “newer” as in the design where driver negative terminal is bridged to threading and circuit is broken by gap at the battery contact(*s) when loosened, relying on a compressible spacer/donut (with hole for pos end battery button) on pos side to ensure gap behaves predictably when in use (turning on and toggling) and eliminate battery rattle.

Ostensibly the “newer” design provides some saving in length since the spacers can be made thinner/shallower than a metal spring can, so I’m guessing this is why it seems to be quite common now. However now that I’ve owned a couple lights using this design (both brand name well implemented version of this style and the *other a cheapo clone brand rendition) I feel the traditional style trumps the possible minor decrease in length.

When done properly this implementation has two clear disadvantages (when it’s not it’s a disaster*):

First, it’s usually a bit of a battery crusher due to needing enough pressure to compress spacer disk esp in combination with using raised bit on neg end to ensure contact (including with deformed or dented batteries).

Second is that since the spacer must (until compressed) ensure a break in contact it has to be a non conductive material (foam/”pu foam spring”) which I suspect is not as resilient as a metal spring, especially since it is by design located next to where heat is generated.

Just putting this out there in case anyone else sees these issues and it can gain enough traction to bring it to the attention of manufacturers. Hopefully they either stick to the traditional design or find some fixes for this.

*In the cheapo clone brand they had no spacer/donut which makes it jump thru modes and flicker due to inconsistent contact until tight, which is a pain both when turning on and when twisting to toggle modes and the battery rattle potentially damages both the battery and pill.

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Thanks for your observations. Lately, I’ve been thinking about these design differences too. From my observations using a Thrunite T20 (battery crusher) and a couple of BLF Mini’s (negative driver contact), I have come to prefer the opposite of you, what you call the “newer” design. Different lights, different experiences, different preferences, I guess. The main issue for me is reliable contact and operation when using various battery types/lengths. But like you said, it really depends on execution. I think the foam spacer is a must in the “newer” design, although I don’t have any experience with battery crushers without one.

One of my BLF Mini’s works great with any size battery I put in it, even long protected 16340’s even though it requires a little more pressure to get the head on. The other one, however, has been finicky with mode changes and flickering regardless of battery size, but it was especially bad with longer cells. I’ve messed around with making sure the driver is flush with the contact ring, adjusting the negative spring position, and even tweaking the depth of the pill in the head. I think the problem was the battery tube threads were just a hair too short to make good reliable contact with the driver, even when empty or with short cells. I ended up adding a thicker o-ring in front of the lens to move the pill back a little bit so the body tube could make better contact without having to tighten it all the way down. So far that has done the trick.

Because of this, I think in general, the battery crusher design is more reliable. It can also accommodate longer cells without a problem. I use protected 16340’s in the T20 and it works just fine, it just doesn’t screw down as far into the body and the brass pill shows a little bit more. I do try to be careful not to over-tighten it though, and so far the battery has been fine. However, I do have to remind other people not to tighten it too much. They really like to crank down on it for some reason. :~

With the recent BLF edition Thrunite Saber 1A deal, I had to consider if I wanted to deal with the “traditional” design again. I ended up ordering one anyways. Couldn’t resist… But reading the recent posts in that thread from people who already received theirs, it seems like a bunch of folks have been having problems. I think there are just too many variables in this design that can be just slightly off that can end up causing reliability problems. That being said, I hope mine turns out to be a good one.

Just out of curiosity, has anybody had flickering or mode change issues with the battery crusher design with a proper foam spacer? (e.g. T20, L10, Sens series, etc.) How about with the negative driver contact design? (e.g. Mini-01, Itp A1/2/3, DQG, etc.) I’m curious if there is a correlation. Maybe I should make a poll???

Come to think of it, I hope the DQG 18650 turns out to be reliable. I haven’t actually seen any pictures of it with the head off, but would assume it is of the “traditional” design. Really hope that one is good too. *fingers crossed

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There’s certainly an argument for liking the break at battery types (more concise description?) it just seems that if both types are executed properly the rear spring/break at driver contact would be more enduring while at the same time gentler on batteries. Though after bodging a *fix on the crappy light without the spacer it’s now in use, which did illustrate that with a broad bottom contact pillar (which it has) it doesn’t really make a noticeable indentation if you’re not the type to crank on it.

My sens aa makes a very noticeable dent at the negative end despite careful use; the bottom has a narrow pillar with leaf springs around, but this winds up effectively being simply a narrow pillar since the donut is dense rubber and requires a lot more pressure to compress than the springs withstand. That aside it is a great light and the direct access+autolevel ui, driver and lens design along with the quality make for a great package. Certainly my favorite pocket light, battery denting notwithstanding. I suspect if it had either a broader solid portion to the raised contact or its current design was paired with a foam instead of a rubber donut it would address the issue and be even better (though the slight delay in turning on in direct access is the first thing they should fix in any update to the series). Personally for long term reliability I’d favor the broader neg contact since rubber seems favorable to softer foam for the reasons I mentioned in the opening post.

In the older type I have a few old lights and a new blackshadow eva, all work flawlessly. I don’t have any cheap lights in this style of twisty but intuitively the design seems subject to less issues (seems like should work reliably so long spring has enough travel to ensure battery is always contacting and the thread depth is enough to bring the contact plate to the lip of the body) so assumed that to be the case in practice. It seems perhaps not.

Regardess you’re certainly right that as end users this is all ultimately subject to how manufacturers are implementing them, so a poll to see which ones are more reliably made would be useful. Just hope the observations we make about why the issues arise in either somehow get back to those that make the lights.

*made a makeshift foam donut, soft foam which makes it operate well but probably won’t be very lasting and comes off easily. It’s easily redone/replaced which is fine for my own use, but it should never have required a fix and is still crap since I had originally bought it to give away not as a chintzy light with maintenance caveats.