First of all, the Wikipedia has a good definition for CRI. It's not the only method of color rendering evaluation, it just is the oldest (and the worst) but still valid. You can for example check “TM-30-15 vs. CRI and the Future of Color Rendering” and “TM-30-15: A New Method for Measuring Color Rendition” (there are further methods too).
As human beings we are adapted to natural light sources: the Sun, fires, and blackbody radiators namely. All these “ideal” light sources have spectral power distributions which allow the average human being to properly discern color information. Light sources whose spectral power distribution differs from ideal make stuff look “less appealing” to us. Here are a couple of videos on this subject:
Also let me say that an LED diode “isn't good at showing the difference among colors” because it's us who, in our minds via our eyes (senses), do that in response to a natural or ideal light source. Some people don't like or need high CRI leds because they are “less efficient”, but this also is rigged or tampered way of looking at the matter because perceived brightness obviously depends on our sensitivity to the different visible frequencies. I don't care about efficiency, those who care can buy some green led and have the best efficiency, at the price of super wrong color appreciation.
Bins and tints.-
Emitter bin is a measure of the relative output an emitter has at its binning current. Thus, the higher bin the higher the perceived brightness. Take a look at emitter datasheets for more information.
Tints are a way to classify an emitter's light output within the color space. Examples:
This is the way Cree does it, same graph as you posted above.
And here is how Samsung does around 4000K and below:
This graph is from LH351B emitter datasheet, hence the 350 mA binning current.
The photos attached at the sales page don't really look like “the real deal”. They may look “sort of”, but take it with a grain of salt.
The reason I suggest “warm” emitters is because it is easier on the eyes to use a warm light source at night. When at night our scotopic vision is active, this is one of the reasons “warm” (what you call “yellowish”) light sources look good. And it also is the reason why “n00bs” wandering with “cold white” flashlights can easily kill your night vision if they focus their flashlights to you directly, it has to do with the amount of emitted green-blue light from their leds. With a warm light source at night you can easily see in the dark without having to turn off the flashlight and waiting for your eyes/mind to adapt.
Yes, Luminus Devices also has emitters above 4000K; and no, lower temperature light sources won't waste battery any less.
The street lights you speak about probably are low pressure “sodium vapor” lamps (colors look like crap with them).
What you say on the topic of foggy yellowish flashlight versus neutral or cool white, hard to say without really knowing what they were using. I have warm flashlights whose output is a good deal higher than most standard neutral or cool ones lumen wise, but the main reason for the phenomena you describe probably is the higher “night vision killing index” of neutral or cool leds versus warm leds.
Biscotti is a microcontroller software for flashlights which Simon uses in his 7135 drivers. Simon said he was working on Biscotti for the newer “SST-40” drivers in his [Convoy] thread. It is also called firmware, as it is microcontroller software written in “low level” programming languages.
The temperature control in the SST-40 drivers prevent the driver (and hence the flashlight) from overheating by reducing the current on demand (55 °C max). In high (5 A) the flashlight would become hot quite fast without temperature protection. It can be disabled by removing the onboard NTC.
Different flashlights implement dimming modes differently, but it has nothing to do with reliability. The amazon sales page torch probably was of bad quality.
Can't really say for sure if the SST-40 driver will shut down the flashlight below a certain voltage, but I would bet on it. Anyway, even if it were not to do it, it is a linear driver; this means battery voltage would hardly drop below 2.5 V even if left on unattended for days (the minimum Vf of standard white leds is close to 2.5 V, this is the reason). Thus, it is safe anyway no matter if you use unprotected or protected batteries.
U2, T6, T5, T4… are emitter bins. They define a relative emitter output at some given current and temperature conditions.
My nephew's flashlight is a green S2+ I custom built from a host with Samsung LH351D 4000K CRI90+ emitter and ∅17mm SST-40 driver. Had it at home recently but forgot to take pictures, sorry.
NKON is a great place to buy cells.
The NCR18650B cell isn't bad, but I'd buy Sanyo NCR18650GA (refurbished units available), Samsung INR18650-35E or LG INR18650-MJ1 (available refurbished) instead.
The Samsung INR18650-30Q is a higher discharge cell. I'd get it for higher drain flashlights (7+ A), although it is a good choice anyway.
The LG M36 is good too (and it actually costs a bit less than the MJ1, wonder why as according to Henrik's tests its performance is about the same as its sibling.
Oh! I don't think you need a protected cell, but if you do, KeepPower does it good without asking too much money (nice example).
Next time one question at a time, I've spent a loong while with this LoL. 
Wed, 02/19/2020 - 04:43