dl12345

Well, if you just set a stupidly high TCR value, like 300, then the mod will think the coil is cold because the resistance will not have risen high enough. In which case it will fire with the full preheat wattage for the full length of time specified and then drop to whatever other wattage you've set. Just make a custom material and specify the the value of 0.003 or even higher if you want. (SS316L is TCR 0.00092)

This fix also stabilised my resistance readings. It's almost like the 510 positive has been extruded and leaves behind a little raised part when the extrusion process is complete. I used 600 grit paper, although it's a very soft alloy, so you can use finer paper. Smoothing it and flattening it makes a superior contact surface.

So I now confirm that my problem seems to have largely resolved itself after doing this fix. Flattening and smoothing down the 510 nub on the connector appears to have stabilised the resistance readings and the temperatures with my 75 are much closer to my 200s when using the same atty, presumably because it's reading the resistance more accurately due to a superior contact surface.

Granted, they're a good vendor. I doubt they're labelling something as SS430 when it's not. Looking at this link I see they've now started listing the composition of the alloy. It's not nickel free....

Correct, it doesn't. But then surely this implies that CW 430 isn't really 430 but something else instead?

I noticed in the last day that when my 75 goes to sleep and wakes up, it resets the resistance as if I am putting in a new coil. For some reason, when doing this (as opposed to having a new coil put in while the device is awake), it appears to consistently under-read the ohms. It only does this when going from a sleep state - my two DNA200s and ohm reader show the same ohm readings, as does the 75 when I put the atty in when the board is awake. If I then take out the atty, reset the resistance with a much higher or lower ohm coil and then put it back in, it reads the original resistance, not the lower value that it did from sleep state. Since the difference amounts to about 0.01 ohm, this would certainly cause a weaker vape. I noticed this post from FairCold and have done the same now to my VT75 nano, as it also had a slightly uneven 510 connector pad - almost as if it had been extruded. I have sanded it down with a 600 grit paper and it is now much flatter. So far I haven't noticed the from-sleep-resistance-drop, although I'll need to test with a variety of different attys over a couple of days.

I tried some 430 but didn't get very good results as the steam-engine profile didn't seem to match the material. I got mine from Crazy Wire Company. Where do you source yours? I'd like to give it a try again as I get better results with SS304 than with SS316L, so the improvement should be even more marked with SS430

Yep, case analyzer run on all three, both 200s and the one 75. Likewise mod resistance has been set with the aid of a plug on all three devices. To the point of the single 18650, I keep wondering if this is the weakness myself; I use a single Sony VTC5A which definitely shows significant voltage sag with escribe, far beyond that of the multi-battery 200s. I'm tempted to jury-rig a multi battery setup for my 75 just to see if this makes a difference. I should probably do this before condemning it out of hand... I have used alternate batteries for the 75 just to eliminate the possibility that the battery is bad (an LG HG2 and a Samsung 25R)

Incidentally, all have the mod resistance set correctly using a copper short-out 510 pin. All hav ehad the case analyzer run and all have correct battery profiles. And they're using the same profile. Perhaps it's down to the 510. The only difference is that my 200s use a decent 510 connector and the VT75 uses a substandard part

I believe I stated, erroneously, in a previous thread, that my temperatures with the DNA75 were the same as my DNA200s (two of them, boxer and wismec modified with a FDV v4). In my defense, this was a day after I acquired the DNA75. Since then, I've had more time to compare the two. At risk of offending some people here, I think the DNA75 is crap, in a word. It requires about 25 - 30 celsius higher temperatures with the same atomizer and coil. In addition, the vape with my 200s is far denser and richer than the 75, even at a temperature setting about 25 celsius lower. With the identical atomizer, juice and coil. I've fiddled with the 75 until it shows the same ohms as my 200s, but still the experience is vastly different. Anyone else with anecdotally similar experience?

I wouldn't even dream of using a staggerton or a clapton SS coil in TC mode, so the point is moot

I also use a toothbrush and dishwash liquid to clean coils. It works a charm. However, my spaced coils are totally consistent in terms of resistance. Every time I wrap a coil I get almost exactly the same resistance, down to the 0.01 ohm level, so for me at least, a spaced coil is far from inconsistent. I think the risk of Cr+6 is low, but it's there and still not conclusively demonstrated that it's non-existent, so personally it is something I prefer to avoid because I can. Anyway, to the OP, despite many people preferring spaced coils for SS TC, there's at least one person here who has experience to the contrary and feels that a non spaced coil is better. It's not an exact a science, so try both methods and see which one works best for you. I'm not dogmatic about it - whatever gives you the best experience and is most convenient.

I avoid burning my SS coils because of the possible risk of release of hexavalent chromium, although to be fair this risk is relatively low because of the high temperatures required for oxidation of hexavalent chromium (someone did some lab tests a few years back and didn't find any after dry burning SS coils). It takes me 5 minutes to make and fit a new coil (about as much time as it takes to to burn one clean and rinse it), so I prefer to err on the side of caution. I also find if I burn a (spaced) coil that the metal becomes tarnished and the coils gunk up much easier. https://www.e-cigarette-forum.com/forum/threads/stainless-steel-mesh-oxide-discussion.362608/ http://www.ecigarette-research.org/research/index.php/research/research-2015/212-db https://hal.archives-ouvertes.fr/file/index/docid/252374/filename/ajp-jp4199303C935.pdf

If you're soldering a complex surface mount chip then you might need a hot air rework station, but just to solder the wire to the tab an iron will do. I'm sure there are others here who are much more experienced at soldering than I am and can probably give better tips, but what i do is to tin the wire first then "paint" the tab with some liquid flux, apply a bit of solder paste to the tab, place the wire against the tab and paste, put a blob of solder onto the tip of the iron and then touch the molten solder to the wire/tab/paste. That generally gives me a nice clean solder that sticks to the tab first time.

I find that solder paste is much easier to use than solder wire when soldering to a surface mount tab. It also gives a neater solder

I own three DNA devices, of which I have assembled one (a Boxer DNA133), completely rebuilt another (a Wismec DNA200) and now I'm seriously thinking of having a part machined so I can rebuild my HCigar VT75 nano. In all cases, the offending part is the really poor quality 510 connector which degrades the TC performance significantly. On the Wismec (both the RX200 I owned and the DNA), the spring loaded pin stopped being spring loaded and I needed to replace the connector. I have a similar issue with the VT75 nano. It's 510 is just crap and the base plate makes inconsistent connectivity with the body. But there's no real space to add a proper Varitube or FDV connector, so I'm thinking of doing something similar to what I did with my Wismec, which is to add a 22mm tube shaped mount on the top of the box to space the 510 further away so it does not impinge on the board. However, with the Wismec it was a little easier (apart from the really cramped space inside the box) - just a small SS tube with a 10mm hole in the top did the trick. With the nano, the tube needs to be threaded and the thread must be recessed. So it occurred to me perhaps I should just 3D print a new box. Can anyone recommend some good 3D printed 2x18650 boxes for a DNA75 (or even a single 26650)? Commercial or creative commons - I don't really care either way. Or even a fully made box (small and 2x18650 is desirable).

You should use a spaced coil if you're using SS316L. Claptons don't work in TC mode. Micro coils also don't work well in TC mode. Personally, I have used both SS316L and SS304 and I find the latter works much better due to a steeper TCR function. I've tried both 28g with 7 wraps and 27g with 5 wraps and the 5 wraps works better for me (about a 0.5 ohm resistance with a single coil) - on the 28g coils it heats less evenly and the centre of the coil gets much hotter than the 5 wrap coil. I've used 2.5mm and 3mm coils and prefer the results I get from a 3mm coil. Daniel from DJLSBvapes did some testing on (I think it was older firmware) and found that using a TCR value gave slightly more accurate performance temperature wise than the steam engine CSV, although I don't know if this is still the case after newer firmware releases. I use the CSVs with no problem and don't notice much of a difference between the CSV and TCR. SS316L alloys vary significantly. I have bought some wire labelled as SS316L that is unusable and others that vape perfectly. If you're having problems and using spaced coils then maybe the wire isn't good. With SS316L you need to be very sure you have a stable resistance due to the very low TCR. Even a 0.01 ohm delta makes about a 10 degree celsius difference in temperature setting. So in a nutshell, the temperature is really just a "guide" - don't rely on it being perfectly accurate.

I had a similar experience. I have bought a Wismec RX200 and a DNA200. On both of the devices, the 510 connection became stuck in the "down" position. On the RX200, the thread was badly tapped and eventually stripped itself. They denied warranty in both cases. In the case of the RX200 they even went so far as to accuse me of using a Smoke TFV4 which they said had a long and unsupported connector. I don't own a TFV4. Eventually I cannibalised the RX200 for parts - I cut down the front portion of the case by using a dremel to remove the 510 mount under the top of the lid then drilled a larger hole and fitted a new FDV V4 510. I also took the sled out of the RX200 and used it for the DNA 200, which required cutting it a bit so the 510 connector's nut didn't impinge against it. The board and battery contacts, front faceplate and battery cover came from the DNA200, so I now have a bastard child of a RX200 and DNA200 Releaux that functions much better than the original due to the far superior 510 connector. When I sent Wismec a photo of the 510 and asked how come two devices had the same problem, they implied user error. So no, not impressed with their after sales service. I had even requested that they send me a new 510 connection which I would fit myself and they refused point blank. As a general rule, the mod manufacturers sometimes take some serious shortcuts. In particular, I don't understand why they insist on putting such poor quality 510s in. It's such an important component that it sure makes sense to spend the extra dollar or so to put in a decent quality part.

I have a Wismec DNA200 which I have completely disassembled since I replaced the 510 connector with a FDV V4 low profile short connector (which required quite a bit of surgery on a donor RX200 case with a Dremel). I have desoldered everything and cut down the battery compartment a little to give clearance for the 510, so I am familiar with the internals. The battery sled design is very poor. Reading your description of what you did to fix it, it's possible that the battery connectors in the top and the bottom of the sled are not making decent contact. The way you describe pushing on the sides fixing the problem seems to point to the brass cup connectors at the back part of the battery sled not making proper contact, as pushing in on the sides will cause the lids on the sled to have less "play" in it and therefore the spring under the cup connectors will force them into better contact with the battery. The problem is likely with the top connectors. Unfortunately the lid at the top and bottom of the battery sled is only fixed on by a single screw that is located towards the front of the apex of the triangle formed by the lid. If the door and case machining tolerance is machined slightly too loosely, then the back part of the lid won't press down enough. The spring loaded cups at the top are at the rear part of the compartment (the ground connector at the top left rear is one of these), so the most likely candidate for this problem. I'm not sure whether this would work, but since it is simple it's worth a try. Cut and fold a piece of paper (as many times as you can and still have it fit in) and wedge it between the battery sled and the top of the case - the paper should only cover the part of the sled at the rear contacts as the screw at the front is good enough to keep the lid firmly in contact with the front connector. This would help to force the back of the lid down and compress the spring more so that there is greater force exerted on the battery. You need a T6 to loosen the screws on the top and bottom of the case in order to be able to remove the battery sled.

Got it, yes that helps a lot. So with a 62W preheat for 1s I'm operating the battery close to it's maximum rated continuous current and slightly over when hitting the soft cell cutoff. Looking at the numbers it would probably be a good idea to decrease the preheat slightly to around 58W so that a voltage close to the soft cell cut-off of 2.75v doesn't cause the battery to exceed the maximum rated 25A continuous current discharge during the preheat period. Thanks for the advice, much appreciated.

62W preheat (sorry, I said 65W earlier but I just checked and it's set to 62W because this should give a theoretical max load of around 20A....) However according the escribe screenshot I posted the current draw shows just over 10A at the 3.4v level, right? Hence my concern....

It actually did have loose board mount screws which I had previously tightened up, so these readings are with the tightened screws. Perhaps I should clean the board contacts. I've already cleaned the threads which came with quite a lot of manufacturing residue out of the box. This is a Hcigar VT75 nano, so the ground connections from the 510 plate and the negative battery contact are via a thread (instead of a soldered connection), which to be honest I don't really like - I'm considering soldering the board ground directly to the 510 base plate but to do that I'd need to drill a hole in the plastic mount that sits just below the 510 plate. The engineering in this mod is ill thought out.

Thanks, it's really helpful to know that the sag is consistent with your cells. You also confirmed what I surmised: that is to say that the sag is so noticeable because it's a single cell device. My soft cell cutoff is currently set to 3v, so I'll lower it as you suggest.

This is a VT75 nano. Yes, I do notice a similar sag when using a Samsung 25R - pack voltage drops to about 3.3v - 34v on a 10A load using a 0.5ohm coil. It happens on the initial draw during the preheat phase (65W preheat, 9 hard). Of course on my other mods the sag is much less noticeable since they're using 2 or 3 cells. Just not sure if this is normal for a DNA75 or points to a battery issue.

This is my first single battery DNA75 mod - my other mods are DNA200s (Boxer 133 and Releaux). With a fully charged brand new VTC5A I'm noticing substantial voltage sag. At 10A current, the voltage is dropping to 3.4V (see photo). On Mooch's battery test of the VTC5A, this only happened when discharging at 40A. Is what I'm seeing "normal" or indicative of a faulty (or possibly fake) battery, or am I just misunderstanding these graphs?