How low can my ohms be?

[Bloodshard]

I've ran the math on my triple 18650 parallel box and it seems my amperage limit is about 45A combined (thats with 5amps removed from each battery) so I'm just wondering how low I can build before I'm being risky... I mostly build at .2 ohms, but the low resistance wire I just got takes an insane ammount of wraps to get there. I havnt been able to find any info on this, and was hoping someone could help me out with this... I'd like to know I'm not going to vent my batteries if I try this wire framed... Cancel that my lowest ohms should be 0.098 (with recalculated amps) (still feels risky for some reason to me)

 

[sonicbomb]

Your mod has a parallel battery configuration, but is it mechanical or regulated? Can I ask what batteries you are using?

I'm guessing it's regulated, in which case the resistance of the coil is unimportant to the mod. So build for heat flux and surface area, there is no need to build low.
Regulated mods separate the input and output voltage, in other words they separate the battery from the atomizer. The only relevant values are the wattage, and the remaining voltage in the battery. The wattage is generated by the mod by multiplying the volts by the amps. As the voltage falls, the mod will increase the amp draw from the battery/s to maintain the selected wattage. You need to know the amp draw at full charge, and when the battery is discharged as this value will be the highest, and make sure this value does not exceed the CDR of your battery.
Most regulated mods are about 90% efficient, so you can factor this loss into your calculations as it will marginally increase the amount of amperage pulled from the battery.

To find the amp draw use I=P/V (-10%)

Eg.
50w divided by 4.2v equals 11.9 divided by 0.9 = 13.22 amps
50w divided by 3.2v equals 15.6 divided by 0.9 = 17.33 amps

With multi battery devices, simply calculate the amp draw then divide by the number of batteries.

This can be be modeled using Battery drain if you don't like simple maths.

 

[Bloodshard]

Your mod has a parallel battery configuration, but is it mechanical or regulated? Can I ask what batteries you are using?

I'm guessing it's regulated, in which case the resistance of the coil is unimportant to the mod. So build for heat flux and surface area, there is no need to build low.
Regulated mods separate the input and output voltage, in other words they separate the battery from the atomizer. The only relevant values are the wattage, and the remaining voltage in the battery. The wattage is generated by the mod by multiplying the volts by the amps. As the voltage falls, the mod will increase the amp draw from the battery/s to maintain the selected wattage. You need to know the amp draw at full charge, and when the battery is discharged as this value will be the highest, and make sure this value does not exceed the CDR of your battery.
Most regulated mods are about 90% efficient, so you can factor this loss into your calculations as it will marginally increase the amount of amperage pulled from the battery.

To find the amp draw use I=P/V (-10%)

Eg.
50w divided by 4.2v equals 11.9 divided by 0.9 = 13.22 amps
50w divided by 3.2v equals 15.6 divided by 0.9 = 17.33 amps

With multi battery devices, simply calculate the amp draw then divide by the number of batteries.

This can be be modeled using Battery drain if you don't like simple maths.

It's unregulated and from calculating I get 0.07 being lowest I should build... Thank you for letting me know the actual math behind it.
Knowing that should help me immensely in the future.

 

[suprtrkr]

.07 is fearsome low. That's the value of the resistance used for dead short testing. Even on a 3-battery mod-- assuming parallel, and top drawer 20A batteries in good condition-- I wouldn't build below about .1 at the lowest. Even that's far lower than useful. On a mech, once you get below about .25 or so, the current values get so high they start to heat the current path, thus increasing the native resistance, and voltage drop robs you of the gain you made building low. You'll get better cloud with coils in the .3 range and more surface area, like Aliens or Flat Bas. Of course, those massive coil builds also increase ramp time. But once you get 'em hot, geez do they cook. The only way you can make those super low builds efficient is custom build a mod so over specified it uses 1/4" buss bar for the circuit, or add liquid cooling like a high end gamer pc, or something. Hhhmmm... or maybe float in a capacitor bank to help defeat voltage sag under load. Whatever, I really think you'll be better off chasing coil surface rather than low builds. Safer, too.

 

[Topwater Elvis]

What specific batteries are you using? ( name brand, mah, other markings on the wrap)
What is the metallurgy of the 'low resistance wire' you're using?

 

[edyle]

I've ran the math on my triple 18650 parallel box and it seems my amperage limit is about 60A combined (thats with 5amps removed from each battery) so I'm just wondering how low I can build before I'm being risky... I mostly build at .2 ohms, but the low resistance wire I just got takes an insane ammount of wraps to get there. I havnt been able to find any info on this, and was hoping someone could help me out with this... I'd like to know I'm not going to vent my batteries if I try this wire framed... Cancel that my lowest ohms should be 0.07 (still feels risky for some reason to me)

To run that kind of power you might as well just go regulated.
You big risk is a short circuit; it only has to happen once.

btw do you have any idea what ohms your box mod including the switch is?

 

[Bloodshard]

Samsung 25R, in a Bunker-Buster, high nickel content, not sure as to exact metallurgy specs in the wire, got it from a friend... And yeah lately I've been trying to go for surface area instead of low ohms, this wire is just such low resistance that I need 12 wraps, I prefer framed coils and it's just hard for me to get .2 ohms off it while framed and still have it fit under my top cap, highest framed and fit dual coil I've come up with was .06 ohm with 7 wraps so far, so I'm thinking I'm just gonna get a bit thicker wire to frame with and try hit around .1ohm

 

[sofarsogood]

I've ran the math on my triple 18650 parallel box and it seems my amperage limit is about 60A combined (thats with 5amps removed from each battery) so I'm just wondering how low I can build before I'm being risky... I mostly build at .2 ohms, but the low resistance wire I just got takes an insane ammount of wraps to get there. I havnt been able to find any info on this, and was hoping someone could help me out with this... I'd like to know I'm not going to vent my batteries if I try this wire framed... Cancel that my lowest ohms should be 0.07 (still feels risky for some reason to me)

I read a lot of ecig news and that includes the stories about accidents. Virtually all the accidents during use have two things in common, mecanical mods and young men. Would you be a young man by any chance?

 

[steam heat]

.07 wow that's low...I just don't see the point in any build under .2 but anyway welcome to the forum and stay safe

 

[Topwater Elvis]

The Samsung 25r's are good 20a CDR batteries, they are not 25a CDr.
Leaving x % of amps under the CDR as a safety margin is always a good/safe idea.
Some folks use 50% others use 20% under the CDR depending on their personal risk comfort zone.

The only saftey feature mechanical's have is the one between the users ears.
Make sure it is plugged in & functioning before you go trying low sub ohm builds, the only thing funner than 1 cell in thermal runaway is 2 or 3 at the same time.

 

[Bloodshard]

I try to keep it safe, my usual builds come out to .15 to .2 ohms and i'm just trying to figure out how I need to build with this wire before I go blowing myself up, it's my first time with low resistance wire, so I really don't want to make any mistakes... I'm currently running a 12 wrap at .2 ohms with the same low resistance wire on my Switch Mod

 

[Bloodshard]

The Samsung 25r's are good 20a CDR batteries, they are not 25a CDr.
Leaving x % of amps under the CDR as a safety margin is always a good/safe idea.
Some folks use 50% others use 20% under the CDR depending on their personal risk comfort zone.

Then I had a dumbass telling me incorrect ...., he said they should be 25A, thank you for clearing that one up

 

[edyle]

Samsung 25R, in a Bunker-Buster, high nickel content, not sure as to exact metallurgy specs in the wire, got it from a friend... And yeah lately I've been trying to go for surface area instead of low ohms, this wire is just such low resistance that I need 12 wraps, I prefer framed coils and it's just hard for me to get .2 ohms off it while framed and still have it fit under my top cap, highest framed and fit dual coil I've come up with was .06 ohm with 7 wraps so far, so I'm thinking I'm just gonna get a bit thicker wire to frame with and try hit around .1ohm

Aren't you going in the wrong direction?
Shouldn't you be using thinner wire.

If you want more surface area use many strands of thinner wire instead of fewer strands of thicker wire.

 

[Topwater Elvis]

The only bunker buster I'm familiar with is a drip tip with that name,
it is a ss beehive style.

I wouldn't use unknown metallurgy iffy, one off, small run 'super wires', there are several that have have come & gone & few of those had metals not suitable for vaping in them.

 

[Bloodshard]

Aren't you going in the wrong direction?
Shouldn't you be using thinner wire.

If you want more surface area use many strands of thinner wire instead of fewer strands of thicker wire.

Yeah that would work better probably I'm just trying to come up with a framed build around .1 - .25ohms that will fit in my RDA... And since I'm out of work right now I don't have the budget to just go out and buy wire

 

[Vaslovik]

For my part I can see no point in making an object of the lowest possible ohms. Just find the sweet spot where it vapes best, wherever that is.

 

[Bloodshard]

The only bunker buster I'm familiar with is a drip tip with that name,
it is a ss beehive style.

I wouldn't use unknown metallurgy iffy, one off, small run 'super wires', there are several that have have come & gone & few of those had metals not suitable for vaping in them.

MOAB or Bunker-Buster I hear it called both, guess it depends on which a person prefers to call it since its labeled with both names

 

[Bloodshard]

For my part I can see no point in making an object of the lowest possible ohms. Just find the sweet spot where it vapes best, wherever that is.

It's not that I'm trying to get super low ohms I'm just trying to make sure I know what NOT to build, knowing my mod and batteries limits is a big must for me

 

[edyle]

Yeah that would work better probably I'm just trying to come up with a framed build around .1 - .25ohms that will fit in my RDA... And since I'm out of work right now I don't have the budget to just go out and buy wire

Well, for what it's worth I think you're heading in the wrong direction.
When I was young, there came a point I had to say, "You know what, I'm going to stop spending so much time doing stuff I can't afford, or wasting time trying to do something with the wrong tools and spend my brains towards something actually productive."

As it is right now you already have a powerful vape and I don't see any reward for taking extreme risk.

 

[Vaslovik]

It's not that I'm trying to get super low ohms I'm just trying to make sure I know what NOT to build, knowing my mod and batteries limits is a big must for me

Well okay, push the envelope if you must.