Jaquith

Eh NO! Not true .. like at all. First, temperatures for TiO2 production would not only ignite your Ejuice into flames it would be more like a Flamethrower and 3rd degree burns as a result. Second, like with any of the 'common' metals, even Ni200, IF you know Heat Coefficient ie the W/mm^2 then you can adjust the wattage (voltage) appropriately. I see all sorts of WRONG information being passed around about Titanium. Titamium is the SAFEST metal for TC vaping and IF you can calculate the H.C. (W/mm^2) its still the safest. Actually Platinum is the safest (Noble metal with no oxidation) but at a cost of around $40-$60 per single coil extraordinarily expensive. SS3XXX is an alloy of Nickle, Chromium and other metals which even in TC leach from the metals. Further, since the TCR/TFR curve is so flat, the temperatures oscillate all over the place, and accurate TC is nearly impossible. Never mind that most SAE 'SS316L' is a close approximation from a Chinese GB standard derivative. Safety, perhaps the biggest hazard is temperatures exceeding >536 F where VG (glycerol) breaks down to Acrolein. For any serious TC user I strongly recommend they purchase their own Multimeter with a Thermal probe. You can find them for under $60 USD and IMO for the money a Klein Tools Multimeter; eg Home Depot has kits with a probe.

Generally mixing metals can have unpredictable outcomes. However, most stainless under normal conditions shouldn't 'rust' as shown. High carbon steel, low chromium or plated will indeed rust (iron oxide). Sometimes excessive heating causes leaching, recrystallization, oxidations, and a general breakdown of alloys. I'd try to repeat the process with each metal individually starting with the 34 gauge Clapton which I'm pretty certain is the culprit. Most of my Clapton wire is Kanthal and I've successfully mixed with Ni200, Titanium and SS316L with no problems. I assume you pulsed your coils white or yellow-white in VW Mode.

That's the 'problem' TC does only see the 'whole' coil(s) .. it looks for X% Ohm Change. The hottest parts of the coil(s) are the Legs and the Center. The right and left sides of the coil are cooler. Try it without Preheat. As you've read, I prefer lower, e.g 24, gauge wire because of the dampening effects. If you want near perfect TC then I highly, as in with the exception of Platinum or TiPt, Titan Wires Grade 1 Titanium 24 gauge wire! 'IF' an RBA has either 1/2 Coils or longer legs then I recommend coils as pictured below (stupid fast examples, lol not my best work):

1A is maximum Input for the DNA 200 board so as long as your iPhone USB is at least 1A that's the fastest the LiPo will charge. In comparison, most PC's USB's are limited 0.5A which will take twice as long to charge. For clarification, even if your iPhone or any USB is 2A only 1A will be drawn by the DNA 200 board, the standard is 5V for charging with a 4.2V limit per cell through the Balancer, and BTW your PC can provide up to the same 5V as a USB Charger.

If you want contact coils, anneal to a high glowing temperature with TC off, retighten posts, disable Preheat period (1,1, 0 seconds), set Power to 100W or more, set temperature to 470° F using scrap cotton and "cotton burn test" until light golden brown. Adjust TCR until passed. DO NOT OHM LOCK! If your Atty is unstable then don't use it in TC .. get a new Atty. Whenever I have a new wire I use a rock solid and resistance stable RDA with one spaced coil until I have a TFR or TCR that I know works! Reduce your variables. Once you have TC stable and an accurate TFR / TCR then dual coils or Tanks or whatever. If you have problems then you know it is NOT a TC issue. I find lower TCR metals or alloys don't do too well with Preheat .. eg Stainless Steel...

If you want 'contact coils' then Annealing, but just know Oxides will form. Info "For sub-critical annealing, heating should be performed to 760-815°C (1400-1499°F), followed by air-cooling or water quenching. This stainless steel cannot be hardened by thermal treatment." Further, most SS wire is from China and SS430 has at least 3 SAE alloys nevermind China's GB conversion. Besides not knowing 'exactly' what you have, for Temperature Control increase (hotter) or decrease (cooler) the TCR until the desired temperature is obtained. In other words IGNORE posted TCR settings .. assuming proper setup and configuration. Tip doing this blind, disable Preheat and set the Power way, way too high relying on TC regulation NOT by some erroneous TCR setting or limited by a Power setting.

To be clear you can indeed have a good TC experience using 'contact coils' however there's absolutely no difference in the hotspots you see using a new Kanthal coiling when pulsing. So you have a couple choices: Annealing or Spacing. The problems with Annealing is: Oxidation and Damaging the coiling. My scope isn't to explain Annealing, Thermal Dynamics, recrystallization, metallurgy, etc all of which are the underlying reasons for Spacing as a reduction to the problem of hot spots. As mentioned, if a dual coil is too cool ( anemic ) and the correct TCR / TFR is selected then either the requirements of Power aren't being achieved or the Ohm's Lock is too low to the actual resistance. Review what I typed before.

Peg is a moron and a swindler. I get the math, and I cringe just at the mention of his name.

Bottom-line, it's more about getting a feeling for your 'board' and its firmware in addition to knowing your wire of choice. Example the reason I like 24 gauge Titanium is because of its higher TCR (0.00350) and the lower gauge stabilizes the energy applied to it. Fast Power adjustments to the wire are absorbed more readily which provides a dampening effect; smooth and accurate temperature. Higher gauge wire reacts faster but at a cost of what I call "TC Jitter" which your sensitive mouth can easily detect. In other words, good Temperature Control is boring. BK picked up on that phrase, but it's true. To sum it up, I don't notice any measurable temperature differences between a single or a dual coil at the COIL. If I do then it's user error on my part: uneven leg lengths, uneven coils, poorly tightened leads, overly stressed or partially cut leads or Atty issues. I have a ton of pictures of cotton burn tests demonstrating even and accurate temperatures. In addition I have a temperature probe...

Most people don't fully understand Heat Coefficient (W/mm^2) which is different than a TCR or TFR, but both are relevant to 'Temperature.' If your dual is 'anemic' then set your (Power) Wattage to something ridiculous and compare, verify conductivity, and your cold Lock. On new builds I always perform 470F cotton burn test. In an 'ideal' world too much Wattage on a 'good' TC board doesn't matter. However, that's a much different wattage than Preheat; it's different because of a flaw in the DNA 200 in that it often over shoots the Set Temperature exasperated with lower TCR metals and or alloys. Stainless steel with its low (any metal alloy

I've been doing dual TC coils since the DNA 40, it's one circuit; one positive and one negative with spliced wire. Assuming the same alloy or same metal the TCR is identical for 30 gauge as it is for 20 gauge as it is for 0.05 Ohm or 0.20 Ohm coil or coils. The problems caused are in the 'skill' of the builder not the properties of the wire. I can make a dual coil out of a single wire as I can have one 'part' of the coil cooler than the other part IF I change the RESISTANCE part(s) of the coil(s). Likewise even in a single coil I can have hot-spots or hot legs .. symmetry and building skill. The net percentage of Base (Resistance, Temperature) to Calculated (Resistance, Temperature) from TCR or TFR table. Example 0.50 Ohm vs 0.25 Ohm Base (0.5, 75F) .. Set (0.75, 500F) is the same as Base (0.25, 75F) .. Set (0.375, 500F). Actual math Calculated°C = (Reading? - Base?) / (TCR or TFR * Base?) + Base_Temp°C Further, you're assuming that all of the CSV (TFR) or even TCR data is correct, it's not, especially in alloy (mixes) of metals. Evenness has more to do with the: how the wire is formed e.g. I'm not a fan of cold pressed; TCR of the metal or alloy e.g. I prefer 0.00200 to 0.00300 or higher (Resistance, Temp); gauge of the wire e.g. I prefer low gauge (24 gauge); electrical flow, coils that are spaced or older are less likely to have hot-spots e.g. ideally I prefer to pulse my coils but that doesn't mean that I have to make them so hot they form oxides but instead to remove stresses either caused through the coiling process or often (cold press SS) how the wire is produced. Lastly no wire is precisely represented as a TCR, a TCR is an approximation often an averaging of the (Resistance, Temperature) changes. Instead, ideally a TFR with many plot points is the most accurate with its irregular 'curve' particularly in the temperatures most people vape e.g. 400F to 600F.

18650 batteries - There are only a few actual, Grade A, manufacturers: LG, Panasonic, Samsung and Sony. Otherwise other 18650 batteries are either rewrapped or Grade B and some Grade C (damaged, used or otherwise poor). I only recommend using new, tested, authentic, safe chemistry and at minimum 20A continuous rated batteries. Examples: LG HG2*, LG HE4, LG HB6, Samsung 25R, Samsung 30Q*, Sony VTC4 or Sony VTC5. * LG HG2 20A and Samsung 30Q 15A offer 3000 mAh at a cost, they're tested safe for 20A continuous but the DNA 200 can draw up to 23A in tests both begin to show degradation at 25A continuous. However, most peak use is 5-10 seconds and the battery's temperature is the root cause of damage. The Samsung 30Q is an under speced battery.

No differences, as long as the coils are symmetrical. There's no doubt that single coil is easier. If the coils are asymmetrical or otherwise uneven or there are differences in connection (eg leads / posts) then there will be a difference in Temperature between the coils.

If setting the fixed TCR made Titanium TC work then my assumption is you either didn't import the Titanium (TFR) CSV file into your Mod or you used the wrong wire profile. The TCR / TFR curve (Temperature, Resistance) is a constant for whatever metal or alloy of wire you're using. The number that changes is the amount of energy consumed to heat the wire to a set temperature; Evolv is Watts or YiHi is Joules.

Every Mod is going to have a slightly different set of calibration numbers .. including identical mass produced Mods. Example if you're pushing 100W and higher a Battery Profile based upon 5A is never going to be accurate. Internal Resistance - no Mod is going to have a 0 Ohm resistance. So then it comes to what number identifies the Resistance the most accurately. I've tested a couple ways and the short answer is no, as in none, Atty's are solid copper or silver or etc. The most accurate TC I've found is to take an 'average' Atty you'd use and silver solder it internally at the 510. This is going to be a higher number than a solid die cut rod. Ideally any Resistance Adjustment should accurately represent the neutral Mod AND Atty leaving only the TC wire resistance changes. Therefore if most of your Atty's are eg SS304 negative with copper positive core then I'd try to find an old simular Atty to solder .. if all SS304 then simularly use it. The differences in Atty's alone can be 0.002~0.004 plus the Mods 510 Internal Resistance. A generic eg 0.003, 0.020, or whatever numbers are blind guesses. Every Mod I have, I run all my own Analyzer tests and rely on no one's generic information. I've found as an end result a more accurate TC and as much as 50° F greater accuracy.