LiFePo cells start off at 3.6V fully charged, that will push enough current through these leds to kill them (see the current/output/voltage graph in the OP)
Could I put a resistor in series with the battery to bring down the current? My shaky understanding of Ohm’s Law is thinking that about 150ohms would be about right?
22 Ohms would do just fine. With fresh cell, it will drive the emitter at 45mA and less as the battery are being used up. Still, if you can afford to do it, a buck converter or at least a linear regulator is recommended to keep the LED drive current constant.
Thanks, I’m a complete noob with all this. I’m going to get some C01s to play with, but I also have some old 2AA minimag hosts, and some plastic AA dummy cells that would take a resistor soldered across the inside really easily.
Unless you can suggest any kind of buck converter with a diameter less than 14mm that I could just put in series? Maximum simplicity is the idea here…
Sure, for the low currents that 5mm leds need, a resistor in series is a perfect way to regulate the current (for high power leds you needs more fancy ways of regulation if you want to maintain more or less constant output). 150 Ohm seems rather high, but you can experiment, you may end up with 10 Ohms or less.
I’ll bet they can be safely used direct drive on two Eneloop or any 2 NiMH or NiCad cells, or two primary 1.5V cells of choice, like button cells or alkaline (but not 2 Energizer Lithium), also probably fine direct drive with a single primary CR123A or any size 3V primary.
Who is the manufacturer of “rngwn’s LED’s?” If they have been named, I missed it. It doesn’t matter to me, but it would be easier to refer to them with the name of the manufacturer, rather than, “these LEDs” and “those LEDs rngwn found” or some arcane code that is effectively meaningless because no one knows what it means. One thing Yuji really has going for it…. easy as hell to know what someone is talking about when they mention “Yuji.” Just a thought.
It’s likely Sophia. But since rngwn found them, have djozz tested them, stocked them and gave them a good naming scheme, I’ll stick to the terms he coined.
This 2$ keychain would be nice for these 5mm Leds if only mounted a real battery and circuit board,
also solar panel is not connect on board according reviews.
And why 3 Leds?
Yeah, that’s probably a working unit. But I trust the customer who took that light apart, uncovering the sad truth. It’s fake all over, not worth of rngwns fine LEDs.