hi there, think I have this right but want to be sure so any help is much appreciated. I’ve just got a vandy vape pulse bf, using an INR 20700 battery. Now, am I safe using 28g kanthal 1ohm coils on a dual build if the battery is supposed to have a 30a CDR and a voltage of 3.6v? Presumably this will give .5ohms resistance which is in the safe zone (as far as I can work out .43 is the maximum resistance I can have with this setup?)
Please help! Mech mod and ohms law
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I assume that the vandy vape pulse bf is a mech, correct?
You've got a problem with your voltage. 3.6/3.7 v is the nominal voltage of most 20700s, which means it's the voltage it spends most of its time at. When you're checking mech resistances for safety, you need to use the maximum voltage since that's when the current will be highest. A fully-charged INR 20700 is at 4.2 v.
Can I ask what battery you're using and if you've checked whether Mooch has tested it? Battery counterfeiting and false advertising is common, so it's best to do everything you can to confirm that your CDR really is 30A.
About the calculation as a whole, I think there's another mistake somewhere. Using a total resistance of 0.5 ohm and voltage of 4.2 v, I'm getting 8.4 amps - certainly reasonable for a 30a CDR battery.
You've got a problem with your voltage. 3.6/3.7 v is the nominal voltage of most 20700s, which means it's the voltage it spends most of its time at. When you're checking mech resistances for safety, you need to use the maximum voltage since that's when the current will be highest. A fully-charged INR 20700 is at 4.2 v.
Can I ask what battery you're using and if you've checked whether Mooch has tested it? Battery counterfeiting and false advertising is common, so it's best to do everything you can to confirm that your CDR really is 30A.
About the calculation as a whole, I think there's another mistake somewhere. Using a total resistance of 0.5 ohm and voltage of 4.2 v, I'm getting 8.4 amps - certainly reasonable for a 30a CDR battery.
This question kinda implies that you are not familiar with the operation of a mechanical mod, and as such should not be using one yet.
Mech mods are generally not recommended for new vapers as they require an understanding of Ohm's Law and using the proper spec batteries.
Mech mods are generally not recommended for new vapers as they require an understanding of Ohm's Law and using the proper spec batteries.
I noticed that no one was chiming in.
Kinda like when everyone steps backwards from the bomb.
Be careful with mech mods.
Kinda like when everyone steps backwards from the bomb.
Be careful with mech mods.
One really really handy thing to have when vaping a mech is an ohm meter. They aren’t terribly expensive. The good ones will also pulse power so you can use it as a build stand to work out your hot spots. I’ve got an older one which doesn’t do that but I see the name coilmaster used a lot around here.
It is theoretically possible to judge a coil’s resistance by length, but frequently there are little hiccups. An ohm meter is just good safety.
It is theoretically possible to judge a coil’s resistance by length, but frequently there are little hiccups. An ohm meter is just good safety.
Hi, thanks for this. It is indeed a mech and you’re right using a voltage of 4.2 I also get the same 8.4 amps but then am I not over the 30A CDR (35.28) or have I misunderstood that part of it?
On the website (gosmokefree) it just lists the battery manufacturer as ‘M’, so not sure whether it will have been tested by Mooch.
On the website (gosmokefree) it just lists the battery manufacturer as ‘M’, so not sure whether it will have been tested by Mooch.
The problem is that it’s not 4.1 OR 3.7 OR 3.0 it’s ALL of them. Batteries are a little like balloons. They start when dead fresh at a maximum voltage of 4.1 and deflate downwards. Also while there is a little safety margin built into battery ratings, running a battery right at its redline is still asking for trouble because that redline decreases over time both as the battery expends energy and as it ages.
Thanks everyone for your help, think the best thing to do is go back to a reg mod and save myself the thinking!
8.4 amps draw on a 30amp battery is fine so don't be be despondent you just have to get your head around the math
Have a look at Mooch's battery test list to know whether you've got a good battery...lot of rewraps and over rating goes on in the battery market....
List of Battery Tests | E-Cigarette Forum
Mooch also has a youtube channel and there are some really great videos which explain ohm's law and how to calculate your amp draw.
Hope this helps and hope also that we haven't put you off mechanicals. We just treat the issue seriously and with respect as the consequences can (it's rare) be catastrophic if you don't know what you are doing
Thanks Charlie, fully appreciate the seriousness of it and like I was saying I’ve got a basic grasp of it but ultimately I just want a decent vape and got stuck on a squonker (my ijoy capo broke and couldn’t be repaired) but maybe too much too soon to move to a mech! I’m sure I’ll come back to it in the future when I can be bothered working out the maths and messing around with coils!8.4 amps draw on a 30amp battery is fine so don't be be despondent you just have to get your head around the math
Have a look at Mooch's battery test list to know whether you've got a good battery...lot of rewraps and over rating goes on in the battery market....
List of Battery Tests | E-Cigarette Forum
Mooch also has a youtube channel and there are some really great videos which explain ohm's law and how to calculate your amp draw.
Hope this helps and hope also that we haven't put you off mechanicals. We just treat the issue seriously and with respect as the consequences can (it's rare) be catastrophic if you don't know what you are doing
Thanks Charlie, fully appreciate the seriousness of it and like I was saying I’ve got a basic grasp of it but ultimately I just want a decent vape and got stuck on a squonker (my ijoy capo broke and couldn’t be repaired) but maybe too much too soon to move to a mech! I’m sure I’ll come back to it in the future when I can be bothered working out the maths and messing around with coils!
Yep...no problem...I use mech's and regulated every day but my daily carry is nearly always regulated...Drag 2 or Vaporesso Polar. If you want a decent squonk mod the pulse X is good and it's regulated. I love my squonkers
Good luck to you
Welcome and glad you joined.Thanks Charlie, fully appreciate the seriousness of it and like I was saying I’ve got a basic grasp of it but ultimately I just want a decent vape and got stuck on a squonker (my ijoy capo broke and couldn’t be repaired) but maybe too much too soon to move to a mech! I’m sure I’ll come back to it in the future when I can be bothered working out the maths and messing around with coils!
Good choice. Mechs have their advantages and disadvantages, you will know the advantages when you need them.
Educate yourself about mechs,battery safety,Ohm's Law and coil building and you can use a mech mod safely.
Pulse BF is as safe as it gets when it comes to using mechs.
If you worry about it, you can just use it at home at a desk until you understand how it works. If you feel the batteries getting hot, pull them out.
Because the body is in plastic there isn't much to short internally. There's a safety latch as well. Being a squonk, you can always slap the side of the mod and the battery will fly out disconnecting any hard shorts.
The only thing not very safe is not 100% knowing the CDR of your battery. But a 20700 will surely have 10A. As I mentioned, just touch your batteries and check if they get hot.
There's this misconception that if you exceed the CDR your battery will instantly explode. That's not how it works. Mooch's CDRs are ratings he gives his batteries where you could theoretically hold the fire button down and drain the entire battery without it getting hot enough to go into thermal runaway. People who know what they are doing exceed their CDRs all the time. But they monitor the battery and check if it gets hot - if it does they let it cool down so it doesn't go into thermal run away. I'm not telling you to do this, in fact I highly discourage you. I'm just telling you so you understand what's going on in your mech mod.
For reference, I use 20700 30A batteries too. I build down to .15 all the time and still have a ton of headroom. But I 100% know my batteries are 30A.
To force a genuine, undamaged, Sony/Murata or Samsung or LG or Panasonic/Sanyo or Molicel battery to go into thermal runaway, it would either require you to cause a hard short or require you to push the battery really, REALLY hard. Many people are still confusing battery thermal runaway with battery venting. Thermal runaway is when the goop that's inside the battery literally catches on fire, basically turning the battery into a rocket engine, and possibly also resulting in a battery explosion. Whereas venting is when hot toxic gas and part of the syrupy goop (that also is toxic) are released under high pressure through the venting disc of the battery after it pops open, if there is a venting disc present in the battery. With the vast majority of round cells, the venting disc is located under the top contact, but there are some exceptions to this, e.g., the Sony VTC5D (Vapcell black 25A 2800mAh) uses a circular score line that's on the bottom contact, as does the Sony VC7, the Lishen LR2170SF, and the Vapcell red 20A 4500mAh 21700.
That said, I don't encourage people to exceed the CDR, but nevertheless I do exceed the CDR myself, and, yes of course so do the majority of mech users. Doing so is not without added risks, yet, despite this, it isn't necessarily always the kind of behavior one would normally associate with foolish daredevil type individuals or maniacs, I vehemently agree with you on this. I also am open to healthy/constructive discussions about how to mitigate these added risks, if enough people on here are willing to distantiate themselves from the classical old frantic taboo atmosphere that, seemingly perpetually in fact, revolves around this particular subject.
Mooch himself mentions in a bunch of videos that his ratings are guidelines - they are no fast or hard rules. That ultimately it's up to the end user to know what they're doing.
I think the problem is you get a lot of people, who often vape on regulated devices, hear that mechs explode as soon as you exceed the CDR; then repeat it constantly to new users perpetuating the myth.
Kind of like how for a long time we had people mentioning coil resistance as a factor when determining what batteries to use in a regulated mod.
Often time when people seek mech advice, they're getting advice from people who have never even used mechs and are just repeating something they read in 2014.
Yes, but IMO part of the problem is hidden in the fact that "to know what they're doing" is still a pretty vague definition. I don't recommend to go above the CDR, just like I don't recommend to smoke cigarettes, but you know as well as I do that people are going to do it anyway so that's why keeping the whole detail typically locked up tight in an ivory tower that's surrounded by a taboo atmosphere is not exactly going to help anyone who wants to learn more about the relative part of relative safety.
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