[Group Buy Interest Poll] Tiny EDC keychain light done right - BLF/Sofirn-style!

You can see the archived poll results on the Wayback Machine:


Sofirn (Barry0892) has plans to make a USB-rechargeable tiny keychain light, and BLF members have the opportunity to influence its design to get it just right!

Preliminary suggested details:

  • Emitter: CRI SST-20 4000K (like the C01S)
  • Reflector/Optics: TIR lens (like the C01S)
  • Charging: built-in micro USB
  • Battery: 10180 lithium ion, maybe sealed to make the light as tiny as possible, but can make it possible for flasholics to replace the battery with some tools
  • Modes: Possibly two mode groups switched by 8 twists; Group 1 = Moonlight-Low-High; Group 2 = High-Low-Moonlight. If board space does not permit multi-groups, it will be only Group 1.
  • Brightness: Not fixed yet, but possibly: Moonlight = 1LM, Low = 10-20LM, High = 150-200LM.
  • Dimensions: Goal is to limit to roughly 40mm x 14mm and ~12g.
  • Price: TBD. Aim is for roughly 10USD, not more than 20USD, maybe lower if the interest list is big.

Please go ahead and:

  • Vote above to indicate your interest and
  • Comment below with the quantity you would buy.
  • Optionally, make your design suggestions.

You may find it helpful to use/quote the response template in the second post.

Have fun!

Response Template (Fill in desired sections)

Quantity I would buy:


NOTE 1: I am not associated with Sofirn in any way. I contacted Sofirn to ask if they would be interested in making an improved keychain light design based on the C01S. Currently, it can be difficult to recommend existing keychain lights due to concerns about quality, design choices, or high prices. Happily, Barry0892 indicated that Sofirn has such plans, which motivated this thread to gauge interest and get BLF involvement.

NOTE 2: Naturally, opinions and needs will vary, so I think it is crucial to have a clear focus on what are the goals of a given design, and perhaps more importantly, what are not the goals.

The following is my personal philosophy on what makes a good keychain light (subject to change :wink: ).

GOAL: To have a dependable and useful light present for unexpected momentary needs, while being convenient and unnoticeable the rest of the time.

Non-priorities: highest lumens, longest runtimes, ideal color temperature or tint, exotic materials

Description of terms:

  • “Useful” means having enough brightness and throw for seeing short to medium range objects (eg. in a closet, basement, under a table, around a car in the dark, a dark alley, etc), and wide enough flood to light up a few meters around and in front of a person when walking in the dark.
  • “Dependable” means excellent design and build quality. Usefulness requires solid reliability—what good is a light whose head fell off, is flakey when turned on, or self-discharged itself two weeks ago?
  • “Unnoticeable” means a strong focus on small size and low weight, which will allow it to be “present” at all times on a keychain without giving it a second thought or noticing that it’s there.
  • “Present” also means it must be low cost so that it is affordable to be carried as a handy tool that can be beaten up on a keychain, not an expensive showpiece item that one would worry about and leave in storage.
  • “Convenient” means USB-rechargeable so that it can be charged almost anywhere (even city buses have USB charging ports), and spare batteries, chargers, and knowledge of lithium ion battery protocols are not needed. Muggle-friendly.
  • “Unexpected momentary needs” means that long battery runtime is not important especially at high brightness. These are simple, daily life moments where a light would be useful, but for which one might not anticipate to bring a full-featured flashlight.

I fully realize everyone has different goals and priorities, especially on BLF. This will not replace a AAA or 18650 light. The idea here is to have a neat little device that will be great for 80% of people, and which would probably be sufficient in 80% of day-to-day casual needs for light. A well-optimized true EDC for the common folk.


If it were a clicky instead of a twisty, I would be interested.

(But I know that's not going to happen.)

I hope it turns out well for everyone else.

… can we put a cap on the number of years to fruition?

Can you suggest a way to incorporate a clicky with the above constraints (particularly size)?

Needs LVP and REPLACEABLE BAT :stuck_out_tongue:

No, a clicky would be much larger, so it won't appeal to most BLF members.

It's just what I really want.


If the battery the battery is included and is replaceable… Interested (voted).

I am interested if

1) The battery is easy to replace.
2) The modes are spaced for my needs. High runtime needs to be atleast 1 hour 30 minutes. Medium around 50 lumens or a little lower.

Would be very interested if it

  • came with Type C rather than micro USB
  • looked nice

In general in lights this small charging adds a lot to the size and if it’s micro USB I’d prefer to not have it at all.

The problem I find with lights of this type is that they’re unusable for practical use. If the high mode lasts for 30 minutes, its useless for me. Then the medium mode is so low that its as good as not having a light at all. The high and medium modes are important to me.

I hope this light is the first to change the mode spacing.

Clickies are large …but tail e-switch (UF-10 style) would add roughly 5 mm to the length without affecting diameter.
18650S style would carry even smaller penalty but would require a custom MCPCB and therefore limit LED swappability,

A tail e-switch would work for me, but I don't know if most people would be interested.

There is no way high mode will last an hour or more on a 10180 battery. I was told the drive for 200 lumens on High is because 100 lumens is not enough to sell and BLF members push for more and more lumens. If you disagree, make your voice heard! If there are enough interested buyers maybe it could change…

Personally I think a High ~100LM and Low somewhere between 15-40LM would be good since there is also a moonlight for the really low mode. With such a configuration, Low would be very usable and offer a good amount of runtime, while still having High for bursts as needed, and having moonlight for really long minimal lighting.

I think having a useful middle brightness mode is the most important one to get right.

What is the value of having a tail e-switch? Where would the keyring go (I don’t like them off-centered)? Wouldn’t it add cost and self-drain issues?

I have my gripe with the SST-20 and this optics. None of my many C01S is in its original condition, so I do not intent to buy another one. Such a small light needs to have a larger, softer spot. IMO.