Am I in Danger? Sub Ohm and Battery question

You seem to have quite a few concerns, John. 67 views and no takers generally means that everyone (capable of answering) thinks you're one of the seemingly endless number of highly dangerous people who want to do deep sub-ohm without actually learning anything before hand, and... no one wants to invest the time.

Without going into the details of why, I sense you are sincere in your desire to learn... so I'll take the time.

Lets see if we can attend to a few of your issues, and get you pointed in the right direction. Apologies if I make assumptions about what you do and don't know... that's the nature of the interweb.

I'm more concerned with what you know and what you have available to you. Do you have an accurate ohm meter... be it a build box or a DMM? At 0.15Ω, if your meter is off by 0.05Ω, your draw can jump from 28 amps to 42 at 4.2V.
If you don't have one, buy a good quality build box, and preferably a decent DMM (with good quality test leads) as well. If you want to get really tricky, Tech-Thing makes a neat milliohm converter module for standard pattern DMMs that turns your two wire DMM in to a poor man's 4 wire milliohm meter.

How are you at Ohm's law calculation... either paper and pencil math, or using one of the may available on-line calculators. I suspect not so much, or you'd not be asking the "is this safe" question... rather doing the calculation and knowing for yourself.
Click on my second sig line hyperlink and have a read... knowledge from people who actually know stuff is better than guessing, or getting incomplete responses from "some dude on the interweb". ;-)

There are so many discussions on batteries these days... what's real and what's BS... I don't blame you for being concerned there. Personally, I use only genuine MNKE, Efest, Sony, Panasonic and AW batteries that I buy from one source... RTD Vapor. I trust Randy to sell only authentic products.
That last bit is about the best you can do these days... buy from a reputable seller like RTD. RTD does sell the XTAR 30A, and they identify them as Sony VTC4 based cells. Re-wrapping is quite the common practice... hell, genuine AWs are "selected" name brand re-wraps.

On your mechs. They are sort of "old style" in the sense that they probably (hard to say with clones sometimes, what you end up with) don't have telescoping 510 pins... just floaters or single screws.
Sometimes what you have to do is create a "dedicated" mech and atty. If you have a gap, shorten the mech 510 top cap pin so that everything ends up flush with selected, dedicated atomizers & batteries. I don't know if your mechanical... but a grinder, file - even course emery cloth will take a 1/16" off the end of a pin. If you do shorten them, get the end as square and true as you can to insure good conductivity.

Why the mech pin and not the atty? Mech pins (like those in your mechs) are just lengths of common metric screw thread, and easily replaced (my local hardware store actually has a decent selection of metric copper and brass screws). Atty 510 pins are often unique machined parts that you can't find at the local hardware store.

If you Google a bit, there's a chart of common vape batteries on the interweb, that includes their actual measured length. It's a bit dated, but you still might find it useful for comparison purposes.

That's about all I have. If you've not found a handy coil modeling calculator yet... Steam Engine (see first sigline hyperlink) is one of the best. Remember, "garbage in - garbage out". If you need help translating the available options, shoot me a PM, be happy to help.

Be safe.

 

State O' Flux covered most of it, but just to add on to it you might wanna do some more research on battery safety... Not just what amp ratings can handle what resistances (any ohms law calculator will tell you that), but also signs that your battery may be heating. Like he said, a hot atty is fine and to be expected (Especially sub ohming... The coils reach 400º+, ofc your atty is going to heat up and possibly transfer some heat to the mod) but if your mod starts heating up, especially in the body/button, then give it a rest. If it happened while chain vaping, it may just be the voltage drop in your mod causing it... If it happened off a few hits, you gotta fix something. Unless you're going by the pulse rating (Which I do NOT recommend for beginners, for this exact reason) then the battery shouldn't be heating up at all... Don't just let it sit and assume it'll be OK next time. Keep your contacts clean (on the mod, specifically the button contacts, the 510 pin contacts, and any where there are threads they should be clean and buttery smooth) or you're going to be getting a higher voltage drop and parts of your mod heating up.

And as far as how you keep your mod semi-unscrewed... That may or may not present an issue. If it's not heating up or sparking and it seems like you're getting a good strong hit, then you're good. If it's getting hot, sparking, or your hits seem weak like the battery is almost dead when you just pulled it off the charger... Then you have an issue.

Also, I'd recommend starting at .3Ω and not just jumping into the .15Ω territory. Sure, your battery can handle it... But your mod may or may not be able to. Take some time to learn your RDA builds, perfect them, learn how your specific mod/atty react to different ohm builds, and go from there. I currently only own 1 mod (my hCigar black copper stingray) that I feel comfortable dropping below .3Ω on. My Hades clone has too much of a voltage drop, and my authentic Kindred just doesn't seem to play well with anything that low. Similarly, my Magma clone handles .3 just fine, but if I drop it below that then the airflow just isn't enough to keep the coils cool and I start to get uncomfortably hot vapor and sometimes even burning even tho everything else is set up correctly. My Mephisto clone however handles .1Ω builds like a champ.

I guess tl;dr would be to take your time dropping below .3Ω, it'll give you time to learn things that you can't just read up on so that way when you do decide to go lower you'll be doing it in the safest way possible.

 

The gap, in most cases is more an appearance issue. At worst, due to limited thread engagement, it can be a continuity issue, or even a situation where a little bump to the atty can damage 510 threads.
Unless you've already tried very low resistance, you won't really notice any hot spots. It's the low resistance / high amperage requirements where mech mod continuity issues become more apparent.
A mech may not reveal a 0.30 volt conductivity loss (as resistive heating) with a 4 amp draw, due to say... poor button quality / conductivity, but when you try to push 24 amps through that same flawed current path... you'll think you grabbed the wrong end of your vaporizer.

I believe I've overstayed my usefulness, so... have fun, be safe.

 

I think a lot of the fear mongering over the Purple Efest are unfounded since your vaping is going to be bursts anyway. Just don't chain too much if you go low. But 0.15 ohm is nowhere near safe for this battery. I am doing 0.23 and I think that's pushing it a bit...Next build I think I'll add an extra wrap try to get it above 0.3

 

Thank you so much State O Flux for the Steam Engine calculator. This link should be red ironed forever on top of the sub-ohm forum. This is a heck of a tool that every vapist venturing to sub-ohm building should be aware of.
Awesome page and awesome helpful.

Thank you kindly sir.