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.