Not sure what you’re getting at. MTN sells legit Li-ion batteries. This is from IMRbatteries.com, which is also a reputable seller:
MTN even provides a link to the test HKJ did on them:
The test is of re-packaged cells, so who knows the actual manufacturer at the time, it is random. In six years their suppliers surely changed, the same with the technology and chemistry.
Personally I would rather buy OEM and know what I'm getting rather than buy seconds. That's a bold statement, however the logistics of selling cells dictates prime cells are sold under the OEM brand as they will command the price, and SureFire, Fenix, etc. rewraps demonstrate this market principal as they sell at am increased price. A prime cell cannot be purchased, transported, rewrapped, and inventoried, then sold at a lower cost than the same cell without that additional overhead (there is no free lunch).
The rewraps may be a reasonable or good value, perhaps even a great value to some depending on how they judge value. I calculate Total Cost of Ownership including overhead, but some people count their time and efforts as free, which in a hobby is completely reasonable.
Comparing Mtn's prices and selection, if i were buying cells in bulk I would probably use Li-Ion Wholesale, if i were buying parts and some cells I'd get it all from Mtn. I believe both companies are providing valuable services and therefore value both.
Mostly I buy from them or Illumn, but imrbatteries.com and 18650batterystore.com are also good suppliers (those two cater more to the vape crowd and have lots of vape-centric rewrap brands, many of which aren’t what flashlight users are looking for). Aloft Hobbies in California is also worth a look although they are very limited in their loose round cell selection - they got suddenly popular as a source for the QB 26800 cells last year and have turned out to be a great small business to work with. Mountain Electronics is also a very trusted source but batteries aren’t his focus - what he does sell will be known high quality, though. If you’re buying a light or something else, then Sofirn/Wurkkos have been providing quite good cells (Lishen I think…or Littokala…heck I forget now but they’re good cells). Same for Neal’s Gadgets as a solid source for OEM cells.
Not for li-ion cells but back in the day I ordered a few times from them, also from brightguy.com who is still around. BJ tends to be overpriced with fleeting stock levels and they seem to mostly stick to the bigger brands with proprietary cells and such (and/or tend to only stock those branded rewrap cells). Pretty solid business with good service, though. They sell on Amazon, too, so check prices in both places for the better deal of the two on any given day.
Well….first, understand that ALL loose round li-ion cells that suppliers buy from the major brands (Samsung, LG, Sony/Murata) are technically “seconds”. They will not sell loose cells outside of contracts to manufacturers, not even the B-grades. What ends up for sale on the market is usually “extra” cells that were ordered for production in packs or other products, then sold off as surplus. That’s not to say that there aren’t unscrupulous sales of large quantities of cells, because that happens a lot, too, but pretty much any time we are buying OEM cells they have been purchased, handled, and resold at least one time prior to ending up in our hands. The quality of those cells we end up with is usually top notch (for their respective grades…) but there’s no guarantee of that because handling and storage conditions and such can affect the cells a little or a lot. Some are even rewrapped with official wrappers and are still the same OEM cells.
Fakes salvaged cells are a whole other story and my gosh some of the fakers have gotten very good and/or sophisticated these days. This is where folks like Mooch are invaluable and many in the vape community that have reason to be much more concerned with fake underperforming cells in their devices that might actually be dangerous compared to what we use them for in lights.
All the other brands….well, they all rewrap something. Some do OEM cells, some do China-manufactured cells (which I guess technically are still OEM cells, just not the big majors), and some do both. Some of these brands have become very trusted over the years, like EVVA, AWP (…R.I.P.), Keeppower, and some others. Vapcell is mostly very trusted but they’ve had several big oopses. Efest, same thing. Using Keeppower as an example, they offer a mix of sources depending on cell size. They use big majors for a lot of cells but y’know that’s pretty limited to just 18650 and 21700 because that’s all the big majors make nowadays (I think everyone gave up on 14500 and there are barely any 18500 left from Panasonic). So the rest are China manufacturers, like 16340, 26650, 18350, and 14500, etc., etc. Some of those are great and darn close to what the majors could provide us with. Some aren’t so great. There are still a lot of junk cells out there but these rewrapper brands are generally steering clear of those.
So…point being…don’t be too quick to write off certain brands without researching the cell(s) in question. They may be fantastic cells either at the same/similar price or a more discounted price offering some value over big majors. What the big majors offer (out their door, anyway) is consistency. With other cells it can vary a little, and with rewrappers perhaps they have a great cell and then can’t get any more of it for awhile, so in a year or two it might be different. This is where testers like HJK and Mooch are so valuable to us, and why repeated tests of the same models every couple years have shown to be helpful as well. Take Vapcell and Efest as examples…each have some cells that I would buy without second thought (and have), but each also have lots of models that I would pass on in favor of something better.
These brands can be trusted suppliers of rewraps, whatever is inside. And no matter who is retailing them you can probably be content that you’re getting something decent and safe (this is about 99% true for Keeppower as well). Compared to the wild wild west that buying cells on Aliexpress, Fasttech, and Banggood is….man talk about taking your chances. 
Richard at MTN is solid…his cells may be a little dated now but he’s always chosen high quality/high performing cells for his stock, just a very limited selection (small business, buying in larger quantities for better pricing). He’s an enthusiast like us, sure wish he still participated in the forum like he used to…invaluable source of knowledge and experience.
Thanks!
I’ll check out Bright Guy website.
Thank you @Correllux, much appreciated!
Agreed, Richard added a lot to this forum when he was active. Very, very knowledgeable!
Glad he still has his business though, since where else can I get S2/S2+ triple spacers? And the MTN MCPCBs are great, along with the MTN-DDm drivers.
Seems strange though that he hasn’t updated his LED offerings to include 519As. I wonder what his business model is these days?
I don’t know. He seemed to ramp way down but never quit. I know he was hit hard by chip shortages like everyone else, and I’m sure the modding market has really dwindled compared to what it used to be with so many lights harder to open or using nonstandard boards and such. I also wondered if the prevalence of Anduril now had anything to do with anything…there were a few kerfluffles over firmwares for awhile and emotions got mixed in there somewhere.