Okay, it’s starting to sound like a design problem.
Perhaps it isn’t as bright on alkalines (due to huge voltage sag), and so it won’t flicker. Flicker might just be a problem when it’s trying to maintain max output (which it should be able to on NiMH, due to lower voltage sag). In any case, this sounds like a problem with the driver they chose to use in the light. Poor tolerances? Poor QC?
I’ve been in correspondence with Sofirn through their Aliexpress store. They have been helpful in discussing a way to remedy the issue.
They have also added a listing specifically for the SF14V2 (mine is the V1 apparently). Physically it looks the same. The differences that I can spot are that V2 is printed next to the logo and the anodization seems to have a glossier sheen.
Mine arrived just Wednesday…. the flickering doesn’t stop — it is not usable on high.
I do NOT see a V2 anywhere…… disappointing that Sofirn would send out an older version AFTER they have produced a new one to deal with this serious defect.
Yep. Maybe it thinks there is an alkaline in there. LOBAT trip at 1.2V would be appropriate for an alkaline cell. I have this light and I have also tried it with an eneloop, and the same thing happened with me. I refuse to use an alkaline battery again. Alkaline cells are the most expensive way to have portable power. I stuck an 14500 in it, and it works just fine.
You can’t really blame the manufacturer. The light works well with a duracell AA, which is that battery that they intend to be used. Not everyone will put an eneloop in there. Even fewer people would put a 14500 Li-ion in it.
Unfortunately, it’s probably correct. The vast majority of people have never used rechargeable batteries of any kind in their flashlights.
I’m not sure what the demographics of Sofirn buyers are, but they’re probably not all flashaholics.
That said, there’s no excuse for not designing devices to accept NiMH batteries. For at least half the capacity, a NiMH cell will be running with a voltage higher than an alkaline. If a device won’t work with NiMH, then it will be giving up half the capacity of an alkaline too. Running your devices only with full alkalines is even more expensive.
Nope, not really, though they can source it for longer:
I just checked my SF14, purchased a few months back. Before I put in a battery, I checked the retaining ring for the switch PCB to see if it was loose and needed to tighten it to be sure of good contact. Then I put in a (not recently) charged 2400mAh Amazon Basics LSD NiMh and switched it on. No problems. Nice steady output.
I left it running, pointed up on my desk. After ~5 minutes, I noticed it was flickering sporadically. Switched off and on again, more sporadic flickering.
Now I’ve gone and tightened the driver retaining ring too. After a a minute, a bout of flickering.
I have a few ideas. I have a Utorch UT01 that I power with the same type of cell. From specs and observations, they both seem to have similar levels of output. I’ve noticed that the UT01 won’t reach its highest mode and/or will flicker sometimes. Tightening the tailcap solves the problem. So, one thought is that part of the problem is resistance and resulting voltage drop at relatively high currents. I note that the UT01 has double tailsprings springs, while the SF14 only has a single tailspring.
This doesn’t necessarily explain why the flickering seems to come and go though, unless the v1 lights also have active thermal regulation, beyond just stepping down on a timer, and end up reducing their current draw to manage temperature.
Some added evidence that supports the hypothesis that thermal throttling may be responsible for the flickering ending once it starts.
Shortly after switching on and going up to turbo/high, my IR thermometer reads a temp of ~70°c from the emitter. The temp drops somewhat once the flickering starts, which isn’t surprising. However, when the flickering abates a minute or so later, the emitter temp stablizes at ~65°c. This is not a result of the driver dropping down a full level, it’s still in turbo/high. If I do a quick press, the light wraps around to low mode.
I may try doubling up the tail spring later tonight.
Also, and this is a mere indication, the user manual (at least the one I have) comes with indications for 14500 batteries and AA alkalines (sometimes it is mentioned “AA battery - 1.2V or 1.5V (nominal voltage)” ). Ni-MH are not explicitly mentioned in the user manual specs.
This is what it is and doesn’t necessarily interfere with the discussion above!