Question Regarding Mech Circuits

[jolly_st_nic]

My Beyond Vapes Beacon mech tube mod came in the mail, and I like it a lot. When I'm vaping on it, though, my one little lingering worry is, what if the coil comes loose from a post in the atomizer? Just wondering if there is any chance of short circuit in that scenario, or does it create an open circuit where current just stops flowing or only flows when the wire is connected to both posts? It seems to me the latter would be the case and the mod would just not fire, or only fire sporadically if the wire still made partial contact, but to no ill effect. Still, I want to be sure.

Other than that, I think I'm all set for safety? I'm running a modest 1.17 ohm kanthal single coil; Samsung 25 amp 18650 with no flaws in the wrap or the top insulator; I check my ohmmeter routinely; everything is making good contact; I understand Ohm's Law and the relationship between current, resistance, voltage. Any other safety measures I'm missing here?

Sorry if these are a stupid question, open circuits vs short circuits etc, but I like my jawbone intact so I want to be cautious, even if it means obsessively checking every 5 minutes to see that the coil is securely screwed to the posts.

 

[r055co]

Always check on an Ohm Meter.

With that said if it's loose your ohms will jump around and you can tell. If it does short you'll get a very nasty burnt hit. So again you will be able to tell. But if you check on an Ohm Meter first and I also test all new builds on a regulated mod first you're fine.

Sent from my HTC 10 using Tapatalk

 

[untar]

Open (or unreliable) circuit is the best case when only one leg is loose. Worst case would be you forgot to screw the coil down and it touches the atomizer cap, then you have your short.

For other mech safety precedures, other than Ohm's law and battery wraps, disassemble your mech regularly to check for defects in the 510 and switch (insulators can tear, mechanics can become dislodged), coincidentally that allows you to clean all contact surfaces.
And of course always transport it with either the switch lock engaged (if it has one) or with no battery installed (battery goes into a plastic battery case for transport, about $1-$2).

 

[ScottP]

OK the answer is, it depends. In an atomizer the whole metal housing is actually negatively charged, and only the center pin and post are positively charged. If the wire comes loose from the negative side then there is no real risk at all and most likely it would just stop firing until the wire touched the negative post again. If the wire comes loose from the positive post AND gets pushed further through the positive post AND makes a connection directly between the positive post and the housing, that would create a short and could be catastrophic, depending on if it is a pure mech or if it has some protections. If the wire comes loose from the positive post but doesn't connect the positive post to the housing then it will also be an open and stop firing. I hope that makes sense.

By the way, this could also be a problem if you don't cut the leads short enough and the positive lead touches the housing. This is why you always check resistance on some device before using on a mech.

 

[ScottP]

Worst case would be you forgot to screw the coil down and it touches the atomizer cap, then you have your short.

To be clear that only happens if the positive terminal is loose. If the negative terminal is loose and touches the housing the circuit still includes the coil and resistance will probably go UP slightly. If this happen on the positive side, the coil is bypassed via the leg and that is where the catastrophe happens. You should make sure both are tight, but the positive side is leaps and bounds more important.

 

[untar]

Good points, reminds me of that always checking the juice well for any trimmed off coil parts is a good idea as well, we had more experienced vapers here short circuiting their mechs that way.

 

[r055co]

OK the answer is, it depends. In an atomizer the whole metal housing is actually negatively charged, and only the center pin and post are positively charged. If the wire comes loose from the negative side then there is no real risk at all and most likely it would just stop firing until the wire touched the negative post again. If the wire comes loose from the positive post AND gets pushed further through the positive post AND makes a connection directly between the positive post and the housing, that would create a short and could be catastrophic, depending on if it is a pure mech or if it has some protections. If the wire comes loose from the positive post but doesn't connect the positive post to the housing then it will also be an open and stop firing. I hope that makes sense.

By the way, this could also be a problem if you don't cut the leads short enough and the positive lead touches the housing. This is why you always check resistance on some device before using on a mech.

Catastrophic is really an exaggeration. Catastrophic is a thermal runaway which would be very difficult since if there was a short the hit would be beyond nasty thus one would release the switch. Not enough time to cause thermal runaway let alone even venting. Unless of course one would have it in their pocket which IMO is stupidity.

Sent from my HTC 10 using Tapatalk

 

[ScottP]

Catastrophic is really an exaggeration. Catastrophic is a thermal runaway which would be very difficult since if there was a short the hit would be beyond nasty thus one would release the switch. Not enough time to cause thermal runaway let alone even venting. Unless of course one would have it in their pocket which IMO is stupidity.

Sent from my HTC 10 using Tapatalk

It is possible with a short in an atomizer to cause a spark inside the button itself, causing the metal contacts to arc weld together. If that happens, you had better toss it like a grenade with the pin pulled because that is essentially what it will be.

 

[r055co]

It is possible with a short in an atomizer to cause a spark inside the button itself, causing the metal contacts to arc weld together. If that happens, you had better toss it like a grenade with the pin pulled because that is essentially what it will be.

Releasing the switch breaks the circuit

Sent from my HTC 10 using Tapatalk

 

[ScottP]

Releasing the switch breaks the circuit

Sent from my HTC 10 using Tapatalk

Yes, IF the contacts don't get welded together. However, if you have two pieces of metal and touch them together with enough current applied there will be a spark that welds the two pieces together. At that point releasing the button will NOT break the circuit. This is how the tool to connect NR-R-NR wires together works.

It doesn't happen with the coil because the current is spread across that resistance.

 

[r055co]

Yes, IF the contacts don't get welded together. However, if you have two pieces of metal and touch them together with enough current applied there will be a spark that welds the two pieces together. At that point releasing the button will NOT break the circuit. This is how the tool to connect NR-R-NR wires together works.

It doesn't happen with the coil because the current is spread across that resistance.

If the contacts weld together you've got much bigger problems than the coils, much bigger problems.

Sent from my HTC 10 using Tapatalk

 

[jolly_st_nic]

What are the chances of that happening in the real world, outside of theory? I've heard of some accidents involving mechs, even a recent fatality, but my understanding is that they almost invariably had to do with people who lacked common sense doing something terribly stupid. That's just my understanding. Is this sort of welding of contacts common or rare? This can happen with car batteries, where a wrench shorts the battery and welds to your wedding ring, and that's pretty scary, but there are ways to avoid it (caps on the terminals, disconnect ground clip first, remove jewelry, etc). If those precautions can make car batteries safe, which hold a lot more power, I would think the risks of something similar happening with an 18650 are very slim in comparison.

I've heard a lot of scary stories. Sometimes these stories cause me unnecessary worry, since these accidents must be pretty rare. On the other hand, those dramatic tales have helped to make me extremely cautious, which further reduces the chances of anything going wrong on my setup. I'd like to be able to take a vape on my mech and pretty much guarantee that it's not going to end in disaster. Maybe in time I'll just be more comfortable with it from lots of experience. I hope so, because I use nicotine to relax, not to worry, and I like the durable, repairable simplicity of a mech vs. a chip mod. For now, I'm going to get an 18500 and use a kick adapter - maybe just ease into using the mech without regulation.

Thanks for these replies. It's pretty interesting to me.

 

[AttyPops]

^^ On a related note, I wonder about batteries themselves, and how degradation plays into it all.

And I'm talking out of school here, since I'm not an ultra-low-ohm mech user, but a guy can "wonder", right? The continual stress of intermittent usage at high amp drain on batteries must collectively take a toll. Sure, some batteries are better than others, but at some point after many uses and recharges, electrolyte degrades on all of them. It degrades with heat too, and these batteries get warm at high amps. I suppose that's true with regulated mods too that draw high wattages, anything with "super crazy octo-whatever" coils.

Although most of the reports I've read...pockets are involved...is that a timing thing, or a button thing? Like...didn't use the locking ring, put it in the pocket like an idiot, and get his pants blown off. Or was it due to timing...done vaping, locks it, puts it in pocket, but battery is "breaking down and going thermal"...battery meltdown/malfunction.

The guy that died was vaping it (so button press at the time).

Just in general, battery stress and heat has to play some part here. Even if a coil is shorted, and you catch it and release the button, it MIGHT not fail...but if the battery is in a poor state, maybe that's the "straw the broke the camel's back".

Just theorizing...

Makes me think about how old and stressed some of my batteries may be...and I vape at relatively low wattage.

 

[DaveP]

Further info here. FWIW.

Mechanical mods, protected batteries and protection chips

 

[Baditude]

More info here:

A Beginner's Guide to Your First Mechanical Mod

• Covers the differences between a mechanical vs. regulated mod, essential safety accessories, optional safety accessories to add layers of safety to your mech, routine maintanance, use of proper batteries, proper ventilation, low resistance vaping, and faux hybrid mods.

Battery Basics for Mods: The Definative Battery Guide for Vaping

• A popular and essential read to understand which batteries are safe to use in mechanical and regulated mods. Includes a frequently updated list of recommended safer-chemistry, high-drain batteries with their specifications.

Explain it to the Dumb Noob: Ohm's Law Calculations for a Mechanical Mod

• As simple as it is to use, some people have a tough time grasping the concept. Recently revised to make it even simpler to understand.

 

[Baditude]

^^ On a related note, I wonder about batteries themselves, and how degradation plays into it all.

The continual stress of intermittent usage at high amp drain on batteries must collectively take a toll. Sure, some batteries are better than others, but at some point after many uses and recharges, electrolyte degrades on all of them. It degrades with heat too, and these batteries get warm at high amps.

Just in general, battery stress and heat has to play some part here. Even if a coil is shorted, and you catch it and release the button, it MIGHT not fail...but if the battery is in a poor state, maybe that's the "straw the broke the camel's back".

Everyone is free to set their own parameters, and I can only say what mine are.

I try to never exceed 50% of the CDR (continuous discharge rating) of a fully charged battery (4.2v). So with a 20A batteries, that would be 10A. An Ohm's Law Calculator tells me that a .4 ohm build is as low as I would want to use.

The reason that I place a 50% limit is because as a battery ages the mAh of the battery degrades, as the mAh degrades so does the batteries c rating (amp limit). So down the road, your 20A battery may only be a 10A battery. Pushing batteries at or beyond their rating ages/degrades batteries much faster than using them at a reasonable fashion.

 

[KurtVD]

What are the chances of that happening in the real world, outside of theory?

Probably very very low. However, if it happens to you, the risk of major injuries is quite high, and that's why it's important to be extremely careful. Just to see what happens, I once shorted a tiny little LiIon cell (about double the size of a fingernail), and it was really impressive how high the flame shot (at least a foot), even though it wasn't charged fully.

 

[Spey]

In an atomizer the whole metal housing is actually negatively charged, and only the center pin and post are positively charged.

Not always the case. Many of us (myself included) run negative contact center pin depending on mech design.

Example(s):
1) I prefer mech vents (actually all mods for that matter) to be located at bottom of device (away from face & body when in hand or in use).
So following additional comments makes sense in my mind.
2) I place battery vents (+) closest the mech vents, so (-) goes twoards 510 pin (opposite of your quote).
3) If device gets dropped with battery installed, I prefer button contact (which is typically wider than 510 pin/screw) to displace drop forces over greater surface area on vent (+) terminal of battery. Therefore less chance of damaging the (+) battery terminal potentially leading to venting.
4) Every battery I have physically seen that has sustained dent damage to (+) terminal (sometimes leading to venting) was installed (+) to 510. More accurately, dent-damaged battery terminals (+) and/or (-) we're typically damaged through contact with 510.




Sent from my PH-1 using Tapatalk

 

[AttyPops]

Probably very very low.

Yep.

==============
HOWEVER, given that there's 10's of millions of vapers, changing batteries X times per day, with Y button presses per day, on various devices....

stuff happens. Occasionally. I think mostly pocket-button-pressing, though.

Some of the shrapnel-type mech stories I've seen look like some pretty cheap mech mods too. You know, the plain copper tube type, often lacking vent holes, and they didn't withstand the pressures of venting. I'm guessing here, but I anticipate most of the major players in the industry have tested their devices with a venting battery or 10.

Yeah, venting batteries still put out a lot of fire/crap. And batteries swell when venting.

We used to have recommendations around here about vent holes/slots. Major thing to look for, and ideally not just a few token ones, but some real ones covering a decent area. In my mod, they're located around/below the bottom of the device at the +pin contact (top loading). Probably some other areas too like the button or usb port. Presumably the pin would at least hold the battery off the vents enough to let the gas out.

I don't think "Hot springs" alone are sufficient protection either. And vents should point AWAY from the user, with what looks/are to be 510 contacts that won't blow out like a bullet (since they point at the vaper).

Baditude's links above (the first one in particular) talks about such stuff.

 

[Spey]

My Beyond Vapes Beacon mech tube mod came in the mail, and I like it a lot. When I'm vaping on it, though, my one little lingering worry is, what if the coil comes loose from a post in the atomizer?

jolly_st_nic,

I am assuming, from various replies, you understand that a loose terminal connection is not likely going to produce a "short". Most likely simply an open circuit, possibly an intermittent open circuit. To produce a short the coil(s) would need to actually move to the point it makes a alternate contact point, and/or there be a switch or battery related issue.

In my experience far more likely a short is the result of secondary contact with post or AFC (Airflow Control Ring).

Example: many times, when attempting to fill the chamber reducing open air areas, it can be overlooked that the I.D. of the AFC is considerably smaller than the size of build deck when building, wicking, testing, seasoning an install. Then the AFC goes on and there is the potential for intermittent shorting of coil(s) to AFC inner surface area.

This is potential issue for those that like coil close to air intake. Same/opposite for those that like coil(s) close to post terminals (center drippers that want juice to hit coils before bottom of deck.

These are my personal examples of issues I pay attention to related to shorting. Not to mention the more obvious like battery wrap, and various insulation related considerations, and or when running differentially sized wires through terminal contacts, 510 height adjustments, etc.

Hopefully some of value here for you ;-)





Sent from my PH-1 using Tapatalk