As far as I can tell, the Thrunite batteries I have are actually Samsung 30Q under the wrapper. I could not find any Samsung batteries that have 3100mah at 15 A.
https://www.imrbatteries.com/samsung-30q-18650-3000mah-15a-battery/
Does this mean that Thrunite is lying by claiming that the batteries have 3100mah when they only have 3000? Also, none of Samsung's batteries are protected. What are the chances that Thrunite added a circuit to the batteries, or are they lying in saying the batteries are protected when they're not?
Thanks,
Mark
This is sort of general response to the issues you raise.
Cells produced by the primary, basic cell manufacturers are produced for a wide variety of applications, of which flashlights is not the primary one, that being more of a 'niche' application.
Flashlight manufacturers want to sell and provide cells to their customers as part of a total product solution for flashlight users. They spec and test / qualify a basic cell that meets all their requirements for use with their products, then contract with a supplier to optimize it for use by their flashlight customers by providing / adding a safety (protection) circuit module, sometimes USB charging circuitry, etc. They then 'package' the product with a wrapper / label for the flashlight manufacturer and provide it to them as an OEM product for the flashlight producer to market with their flashlights, and critically,
one they have the confidence in to put their valuable name on.
This is what all the U.S. flashlight manufacturers I'm aware of who sell Li ion cells in their product line do (like Surefire, Streamlight, etc.), and also 'off-shore' flashlight manufacturers with a major U.S. market presence (Fenix, Thrunite, etc.) Offhand, I can't think of any exceptions. They do the specification, testing, qualification work, and choose an OEM supplier who can provide a product that meets their standards to provide it. The flashlight manufacturer has all the incentive in the world to ensure that all that's involved in this OEM process is done to a standard that they are prepared to put their good name on, as their reputation then depends on that. I have a single point of contact / support / responsibility, and specifications, and it's the company whose name in on the finished product.
This is, in general, not unique to flashlight manufacturers. This is pretty much the way industry works. Not every product manufacturer can produce every part of their product that's required. The thing that makes flashlights and cells a somewhat special category is the fact that the cell is a visible and user-replaceable part of the product which they sell separately, and which has their name on it. Many OEM parts in many products do not bear the name of the end product producer on them, which makes the case with flashlights and cells different from some other things (such as a hydraulic valve used in the guts of my car, for example).
I'm an electronics industry technical professional, so this is SOP for me. However, I do not try to reverse-engineer products, much less components of products, to determine their suitability. I buy flashlights from suppliers I have confidence in, and I have confidence in them to do their work correctly and up to a certain standard (which in my case is fairly high). I have confidence not only in the 'top level assembly' product that I purchase, but also its component parts and replacement parts, including those produced for them by OEM suppliers. If I didn't, I wouldn't buy their product (in this case flashlights). I have confidence that these products generally perform as advertised and meet their stated specifications / ratings.
In other words, I rely on the manufacturers / suppliers of the products I buy to not only know what they're doing, but to do what they claim to do, and do it properly. If I trust them to build / produce my flashlight, I trust them to do the rest of their jobs properly as well. Again, if I didn't, I wouldn't be buying their products.
I do test the cells I buy using basic equipment (such as so-called analyzing chargers) to 'sanity check' this stuff to ensure that it performs within a reasonable tolerance of claimed performance. These cells are also independently tested by others more exhaustively, and I also rely on their testing for further confirmation. Empirically and from my experience, I've found that I'm generally getting what I'm paying for, the products do tend to perform close to specification, and I've evidently done a pretty good job of choosing my suppliers / manufacturers so far! EDIT: Note that I do use OEM cells provided to one manufacturer in another flashlight manufacturer's flashlights (I'll use Fenix-branded cells in a Streamlight flashlight, for example), but that doesn't change the basic principles here, it's just an extension of them.
One shouldn't need to reverse-engineer products they buy to determine their suitability. I don't, nor do I have time to do that, nor do I want to. I'm paying my supplier / manufacturer to do that work. I pay a bit more for the cells I buy to get that, but I'm getting my money's worth for what I spend.
Hmm, exploding batteries do seem deadly. Just did some research and they don't look fun. I've bought 15+ batteries from Thrunite before though and have had no issues, but it would be good to check any new brands that I get. 
