Help! Sub ohm saftey.

[Inception]

I need help figuring out what ohm reading my coil is at and if it is safe with the battery I am using.

the build is a 22g kanthal wire sleeper dual coil with 7 wraps each.

This is the battery I am using

it doesn't say anywhere on it about the mah. . Also the ohm meter I was using cut out on me when I made this build. What should I do?

 

[Lessifer]

I THINK those are 20A batteries, 1500mah MNKE IMR 18650, 1500mAh, Flat Top

As for the resistance on your coil build, the only way to be sure is to measure it. When you say the ohm meter cut out, did the battery die or something? You should get a digital multimeter, you don't want to fire a coil without checking the resistance. You can also use it to check battery voltage and continuity.
1. You need to KNOW the resistance so you don't overdraw on your batteries
2. You need to know if you accidentally created a short somewhere.

 

[Equilibrium]

Very simple answer...... get a digital multimeter or an ohm meter, then you can tell us what the resistance is.

 

[DoubleEwe]

If there is any doubt in if your battery can handle the draw then don't build so low.

Your coil build (depending on diameter) is going to be around 0.2ohm.

 

[Topwater Elvis]

The battery is a 1500mah 20a CDR.
No way to tell what the resistance is without an ohm meter.

 

[Inception]

Yeah I tried replacing the battery on the meter and to my luck it did not work. I could hoot it up to a voltmeter and do some math. I'm going out to invest in a multimeter today then. Thanks guys. I mainly needed to know the mah of the battery so I can calculate the resistance of the build.

 

[Equilibrium]

Just for giggles..... those look like "macro coils" so.... ~3 mm, somewhere around ~.8 ohm

 

[Kaezziel]

Yeah I tried replacing the battery on the meter and to my luck it did not work. I could hoot it up to a voltmeter and do some math. I'm going out to invest in a multimeter today then. Thanks guys. I mainly needed to know the mah of the battery so I can calculate the resistance of the build.

How does that work out? Especially when you shouldn't put power to the coil without knowing the resistance ahead of time.... mAh of the battery only tells you how long the battery will last at a given rate of discharge....

Kinda like asking the size of the hole made by a hollow-point bullet so you can figure out what gun it came from... without knowing what material the bullet passed through nor the rate of expansion...

 

[Lessifer]

You can plug the build data in here Coil wrapping | Steam Engine | free vaping calculators to get an estimate, but again, for safety, measure first.

 

[Equilibrium]

You can plug the build data in here Coil wrapping | Steam Engine | free vaping calculators to get an estimate, but again, for safety, measure first.

The steam engine site is very accurate ON PAPER. It will get you very close. I use it all the time. BUT... it can't tell you if there is a short or even what the actual resistance is. I use it when I want to try something new and it always gets me in the ballpark. BUT I always use a meter after I build and before I fire it on a battery.

 

[DaveP]

You are using an lMR battery, so that's better than using a Li-ion. Not knowing your resistance is an issue. Even a $10 voltmeter from Harbor Freight would give you good information about your coil. You do know about subtracting the lead resistance when you make a measurement, don't you? Lead resistance is typically about .4 ohms, so failing to subtract it could make you think your coil is .6 ohms when it's really .2 ohms. That could be a mistake that sends you over the same limit of your battery.

Knowledge is safety when you are winding your own coils, but when you get below 1 ohm in a coil safety and knowledge becomes a critical factor. Be careful!

 

[Inception]

. I'm trying to build a equation using number of wraps and thickness of the wire to a proximate the resistance of the wire. I needed to know the mah of the battery to know what the safe One of the battery is

 

[Inception]

Zone. Not one.

 

[Inception]

I thought I could find the resistance using the mah but that was just a brain fart

 

[Equilibrium]

. I'm trying to build a equation using number of wraps and thickness of the wire to a proximate the resistance of the wire. I needed to know the mah of the battery to know what the safe One of the battery is

Coil wrapping | Steam Engine | free vaping calculators

 

[Inception]

Oh thanks

 

[Lessifer]

Knowing what your build resistance SHOULD be is nice, knowing what it ACTUALLY IS is crucial.

 

[Kaezziel]

Your safe zone for that battery is anything above 0.25 ohms. It is a 20A battery... 0.2 ohms puts you at 21A... at least 0.25 would give you a small cushion at about 17A
Basically, it all boils down to... you need to know the resistance of your coil before you go any further... you can only safely do that with a meter/reader

 

[DaveP]

Using calculators to create coils is a great theoretical guideline, but the reality of a build includes such things as a shorted leg or some other factor that could change the result. When you are installing a coil on a mech, a short can create heat, smoke, and battery venting. On a VV mod, you just get a code on the display.

Know what you have before you apply power. You safety depends on it.

 

[Papa Lazarou]

Once you get into extremely low resistance coils, the resistance of the mod itself is more of a factor. Lets say you have a 0.1 ohm coil, and the resistance in various parts of your mod (threads, the switch, the atty connector, internal battery resistance etc.) comes to 0.2 ohms, essentially one third of your battery power is going into the coil, and two thirds of it is just wasted, heating up your mod and battery. It's really inefficient. Some of the things being done these days with "super sub ohm" and what not is not cool IMO.