Convoy S21B CULPM1.TG 12 groups starts malfunctioning at 3.5V

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delphi
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Convoy S21B CULPM1.TG 12 groups starts malfunctioning at 3.5V

Hello guys,

I recently bought an S21B and a new Samsung INR21700-40T 4000mAh and i notice the following issue: When the battery drops to 3.52V, the half press mode advancement starts not to work properly. For example, if i ‘m in group 2, mode 2 (1%) and i half press to go to mode 3 (10%), the led goes out. If i then fully press the switch TWICE, one for off, one for on, THEN the led turns back on on mode 3 level as it should. OR, again from mode 2, i half press, the led goes out, i half press again and the led turns on on mode 4, like it has skiped mode 3.

I then recharged my battery with my XTAR VC4, the charger reported 2500mAh to almost full and now the flashlight works again normally on all modes. So, it looks like this flashlight cannot use the last 1500mAh of the battery properly. That’s 37,5% of the batttery capacity.

Do you think it’s a defective unit or it has to do with the forward voltage of CULPM1?

In comparison, my C8+ SST40 or the S2+ XPL HI start blinking at high levels when the battery reaches 3.15V.

Thank you.

Correllux
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Have you already cleaned bare metal contact areas, checked retaining rings for tightness, and (since it’s a new light) checked to be sure there are no stray bits of metal dust/chips left from the machining process? The latter is common with many Convoy lights and some other brands. Usually odd behaviors like this are simply from loose retaining rings, sometimes really grimy threads or where a lube that’s not so electrical-friendly was used.

delphi
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I unscrewed the light to check. There is no evident metal dust i think. Should it be found in the lube of the threads? Also, the 2 retaining rings seem tight, but of course i could try to tighten them with a tool. When you say bare metal contact areas, you mean the threads of the body?

Correllux
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Oh, just anywhere a little speck of metal might end up in a bin of parts. Smile Bare metal…anywhere that isn’t anodized and in these types of lights is thus carrying electricity. Usually grimy threads aren’t a big deal once you tighten them up but sometimes it affects things. The end/ends of the battery tube are also important to keep clean. It wouldn’t hurt to just remove the switch, check for bits, wipe it clean, and reinstall. Takes just a couple minutes. There’s a chance you have a wonky driver but these are the first things to check and it seems like almost always they solve people’s issues. Could use another battery as a test/check, too, if you have one, but that’s very unlikely to be the problem. You could also unscrew the bezel and remove the optic for a peek at the emitter and mcpcb…wouldn’t think anything up there would be a problem with this but again, stray bits or even solder spatter, or a bad solder joint on the wires can cause troubles. I’d look at cleanliness and the switch first, though.

For the retaining rings, snap ring pliers are best and give you a secure grip. Some of the holes/dimples in the Convoy rings are kinda small so make sure the tips of the pliers fit in them. Some people will grind/file the tips of some cheapie needlenose pliers…tweezers are not ideal and you can’t get the rings as snug with them usually, but in a pinch you can use those. A couple of nails or screws in a board or plate strong enough to withstand some pressure is something easy to make, too. If you need to buy some snap ring pliers, they’re pretty cheap at a harbor freight or on amazon (7” external handles the majority of things, but sometimes internal is more helpful and smaller 5” usually has smaller tips…can get straight tips or bent tips (I prefer 90° bent most of the time). But try to snug them up with a tool if you can. They may not be loose-loose but sometimes just a little nudge tighter is all they need. Kind of like a jumper cable clamp on a battery post…sometimes electrical connection improves with just a little adjustment/contact.

GENZA
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I just bought a Convoy S21B CULPM1 and I also had the same problem when the battery was at 3 flashes apart from that the corona was also very messy.

delphi
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Yes, mine is a little bit off center too.

GENZA
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As for the messy beam, I can still ignore it because even with the messy beam it still throws better than the SFT40 on my S21A but the malfunctions or disappears modes when the voltage drops is very annoying because even when I choose group 12 sometimes the flashlight doesn’t turn on immediately I have to half press or full press the button again.