A question about resistance for box mod running on 2 batteries

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Mackenchiz

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Jan 21, 2015
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I bought a Dimitri Box mod along with 2 Efest IMR 18650 3.7V LI-MN 35A batteries.
This would be my first time to use a box mod with 2 batteries running in parallel and is confuse as to what resistance should I use for this mod. I used to vape on a telescopic mod and it would only use 1 battery.


I found this vaping Chart (link below) and would request some clarification.
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Here is the part that I'm so confused about.

Since my box mod would be running on 2 pieces of 3.7V batteries, what is the lowest resistance that I can use for my coils?
I want to get some good vapor production and flavor as well.


Base on the chart, it shows that 1.70 ohms would still be on the green zone for a 3.70V battery but since I would be using 2 of them on my box mod, can I go lower than this value for sub ohm?
And in terms of resistance, what's the lowest and safest can I set my coil for sub ohm?
 

CoilinTrouble

Super Member
Jan 17, 2015
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Lebanon, Indiana
First off those Efest 35amp batteries are really just rewrapped 20amp batteries, not really rated at 35. Secondly, 3.7v batteries have a full charge of 4.2v. Third, if you have a 20amp CDR battery now the lowest resistance you can go down to is 0.21Ω. Last it depends on your mod but from my understanding with a parallel battery setup you should be able to run double safely, so a 40amp CDR instead of 20 amp, so your lowest resistance should be 0.105Ω. Someone correct me on that if Im wrong. But really theres never a need for going that low in resistance. Its an incrediy hot and uncomfortable vape. With a VV/VW APV you can simply build a higher resistance coil (I run usually a 0.4-0.6Ω), crank the watts and have a similar effect to a deep sub ohm coil. Do yourself a favor and perouse the battery, coil, and ohms law safety threads in the forums and build safe.

Edit: Btw do yourself a favor and grab yourself some better batteries (Sont VTC4's, LG HE2's, or Samsung 25r's. I'm partial to the Samsungs)
 
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Mackenchiz

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Jan 21, 2015
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Wow. That was fast. :)

I actually just bought this efest for temporary use and sort of a backup. The store I went to had run out of stocks for the Samsung 25r's, but I have already reserved for 2 of them which should be coming in within 4 days.

So just to check if I understood this correctly, I'm fine setting the resistance on my coil lower than 1.70 Ohms?
I honestly don't wish to go on the 0.50ish value, I'm just aiming to get 1.0 ohms to 1.2 ohms but just wish to check in first with the experts before doing so.

Thank you so much for sharing your thoughts and suggestions.
 

RamShot Rowdy

Battery Police
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Check out my Ohm's Law 101 (Link In Signature), it explains how to calculate a safe resistance for your battery. Those are probably 20 amp CDR batteries like Coilin said, so keep that in mind. I believe, in a dual batter parallel configuration, current load is shared between the two batteries. So you could probably build pretty low. If you're looking to build at 1.0 Ohms or higher you are very very safe.
 

Rsunderl

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Hi Text_Here and welcome to ECF!

Good advice above, and here's a good thread about why sub-ohming isn't necessary with VV/VW devices:
My thoughts about sub-ohm and latest VV/VW devices...

Hope it helps and Happy Vaping!
 
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BigEgo

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Oct 12, 2013
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View attachment 417644
Hi Text_Here and welcome to ECF!

Good advice above, and here's a good thread about why sub-ohming isn't necessary with VV/VW devices:
My thoughts about sub-ohm and latest VV/VW devices...

Hope it helps and Happy Vaping!


Yeah, your post is pretty much spot on and anyone with any sort of physics or electronics background. People with such backgrounds will instantly understand that the typical "wisdom" in vaping is just wrong. In bodybuilding, they call misinformation and pseudoscience "broscience." For instance someone will say "Bro, you need 400 grams of protein a day to maintain that mass." It's bullchit, of course and why it's deemed broscience. I just find it interesting how various subcultures out there have their own versions of broscience.

As for me, I do build sub-ohm on my VV/VW devices because 1) I am lazy and 2) the ramp up time is slower on high-res builds UNLESS you have really high gauge wire on hand (which I don't). I definitely want to experiment with high voltage/high ohm setups once I get around to buying some thin wire.

I think a lot of people don't realize that voltage and wattage aren't what you need to consider in relation to battery safety. The battery's health is only reliant upon the current drain. If you can vape at a high resistance and a high voltage, it dramatically reduces the current being pulled from the battery. And when it comes to accidents, current is what you need to worry about. If you're only pulling 8 amps and blowing clouds, that's certainly preferable to pulling 20 amps for the same cloud.

This brings me to something else: almost no VW/VV mods have an amp reading. Along with the voltage, wattage, and resistance reading, they should throw in what amperage the battery will be drawing for a specific build. This might make some people think twice about super sub-ohm builds, even on a regulated device.

I know I am preaching to the choir, so this isn't directed at you, Rus, but just some general musings here. Let's do an example:

A lot of people seem to like to vape around 25-30 watts on some sub-ohm builds (say .5 and above). You get decent clouds and flavor on a lot of the subohm clearos like the Subtank. Well, imagine if you're using a newer VW/VV device. Most of these newer devices can push 8-10 volts nowadays. My IPV can output 8.5 volts. Now, imagine using the Subtank with a 2 ohm coil like all the older tanks used to use by default. Same coil head, same tank, same airflow, but higher resistance.

Now, on the .5 coils at 30 watts, you are pulling 7.7 amps from the battery. Nothing dangerous, certainly, but it is consuming a decent amount of battery power each time you fire.

Now let's compare it to 30 watts on a higher res coil. If you run a 2 ohm coil at 30 watts, that requires 7.7 volts (well within the range of modern VV devices). However, the amperage draw is almost half of that of the .5 coil. Your battery will be pulling 3.9 amps.

Why does this all matter if the vape is the same between the two builds? Two reasons:

1) Safety. The less amps you draw, the safer your battery remains. The .5 build at 30 watts isn't dangerous for quality batteries, but lower ohm builds (0.2) certainly can be.

2) Battery life. If you can get the same vape by drawing less amps, why wouldn't you? The less current you drain from the battery, the longer your battery will last per charge.

It's a win-win for everyone if the whole "sub-ohm" culture would just go away. If you prefer mech mods, cool. You are forced to sub-ohm, but we shouldn't be suggesting it to people with VV/VW devices. Instead, we should have people experimenting with high res builds to see what sort of clouds/flavor/response time they can get out of said builds at high voltages. Assuming the wattage is high enough to compete with sub-ohm builds, assuming the airflow is good, and assuming the coil has a good surface area, I see no reason it can't be just as good as a subohm vape.

What the mech mod people need are higher voltage batteries so they can go above the 3.7ish volts and put less stress on their batteries. Perhaps the demand will be there one day.
 

Topwater Elvis

Vaping Master
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Dec 26, 2012
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The Dimitri is a dual battery mechanical with no safety features of any kind, it uses a switch / button capable of handling any amp load 2 batteries can provide.
It is designed to be used by very experienced folks that already know how to prevent having not just one but two batteries vent while holding and placing the thing to your face.

Your safest bet is to build .8Ω ~ 1.6Ω until you gain experience with a dual battery mechanical.
The batteries must be a new matched pair, battery voltage must be checked with dvom when removed for charging to see if there is a v difference & after charging to ensure there is not a v difference, batteries must be rotated inside device with each recharge...etc.
 

Mackenchiz

Full Member
Jan 21, 2015
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I greatly appreciate all the answers that you all have provided. This is certainly a good learning experience for me. I actually build my own coil, I started with the CE5, then to a Vivi Nova, and currently to my very first rda, the plume veil. My preferred resistance would normally fall anywhere between 1.8 to 2.2 since I love cooler vape. I'm just a bit curious to learn as to what's the safest resistance for a mod running on 2 batteries since I only had a telescopic mod that runs on a single battery and I though it wouldn't hurt to seek information first before building my coil that will run on 2 batteries. But after reading all these detailed answers, I'm more at ease.

Thank you all so much.
 
Feb 26, 2015
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CoilinTrouble

Super Member
Jan 17, 2015
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Lebanon, Indiana
Lol 0.09Ω must be a really hot vape, and still better be careful with that setup as you never know when a problem will arise. Ive built down as low as 0.095 before but find no reason to anymore. I just build around 0.4 and if I want warm, huge clouds I crank the wattage up on my Sigelei 150 and bam, same end result in a much safer setup
 
Feb 26, 2015
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6
Livingston TN
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Feb 26, 2015
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6
Livingston TN
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Feb 26, 2015
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6
Livingston TN
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Feb 26, 2015
33
6
Livingston TN
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Feb 26, 2015
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Livingston TN
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