Fairly new to the ohms law

[Locomotion]

I've been building my own coils for about a month trying to figure this ohms law out as a builder.I know of the some what basics but one thing I want to master is knowing what my ohms are going to read before I build them.Its tricky because I'm new to this but I know what a single coil reads a dual is half the ohms.I prefer vaping at higher ohms lower builds of mine don't produce the vapor enough without jacking up the wattage.Nothing against those who like that I preferably stay around 70 to 75.Back to the ohms law what I can't get right is mm to length of the wire do I actually need to buy a ruler just to master this skill.Some things I know feel free to fill in.

 

[inspects]

Have you tried one of the online sites like http://www.steam-engine.org/coil.html

Put in your wire and numbers you're looking for, the software calculates the wraps, et al.

 

[KingPin!]

What are you building on atty wise?

Also what device will be powering a mech or regulated mod?

 

[Synphul]

Another vote for the steam engine calculator. It comes pretty close, once you fill in what type of wire, the gauge of the wire, inner diameter of the wraps and leg length (ends of the coil that stick out to attach to the posts). Generally the lower resistance builds do take more power but it depends on the wire. Stainless steel has a lower resistance than kanthal but has less wire mass at the same resistance so it should ramp up faster.

Not sure what you meant by 70-75, if you meant you prefer your coil resistance to be around 0.7 to 0.75 ohms or if you meant you vape at 70-75w. I used stainless steel as the core wires for my fused claptons, 3x 28ga wrapped with 38ga ni80. In dual coil configuration they come out to .11 to .12 ohms and 75w heats them up fairly well. I'm sure if I used thicker kanthal to get the same resistance it would take more power.

 

[Locomotion]

What are you building on atty wise?

Also what device will be powering a mech or regulated mod?

Currently the vgod pro

 

[Locomotion]

Another vote for the steam engine calculator. It comes pretty close, once you fill in what type of wire, the gauge of the wire, inner diameter of the wraps and leg length (ends of the coil that stick out to attach to the posts). Generally the lower resistance builds do take more power but it depends on the wire. Stainless steel has a lower resistance than kanthal but has less wire mass at the same resistance so it should ramp up faster.

Not sure what you meant by 70-75, if you meant you prefer your coil resistance to be around 0.7 to 0.75 ohms or if you meant you vape at 70-75w. I used stainless steel as the core wires for my fused claptons, 3x 28ga wrapped with 38ga ni80. In dual coil configuration they come out to .11 to .12 ohms and 75w heats them up fairly well. I'm sure if I used thicker kanthal to get the same resistance it would take more power.

Yeah I meant vaping at 70 to 75 watts.

 

[KingPin!]

Currently the vgod pro

and the mod?

 

[Locomotion]

and the mod?

Vaporesso 220w

 

[KingPin!]

Cool in that case the reason I asked is the resistence doesn't matter so much for a regulated mod but it does affect how long the battery will last though before you get the low battery message

I imagine that mod fires as low as 0.1 ohms and has a low battery cut off around 6v as batteries will be in series. if it's a bit more say 6.4v you can up the resistence range below. It should detail somewhere what the low battery cut off is.

If your are vaping around 75w

Square root of power (wattage) x resistence will give you the Voltage

75 x 0.5 = 37.5 and it's square root = 6.12v

So if you want to get the longest time out of the batteries you are using build between 0.1 and 0.5 ohms

Works differently on a mechanical device so don't apply this for that

Are you using decent batteries.... Samsung 25R/ 30q, Sony VTC6 for instance?

 

[KingPin!]

To get full wattage range of that mod build between 0.1 - 0.16 and use a battery like Sony VTC5A above 125W

 

[BoomStick]

Cool in that case the reason I asked is the resistence doesn't matter so much for a regulated mod but it does affect how long the battery will last though before you get the low battery message


So if you want to get the longest time out of the batteries you are using build between 0.1 and 0.5 ohms

If variable wattage is used, resistance has absolutely nothing to do with battery drain rate. You’re passing bad info.

 

[Locomotion]

Cool in that case the reason I asked is the resistence doesn't matter so much for a regulated mod but it does affect how long the battery will last though before you get the low battery message

I imagine that mod fires as low as 0.1 ohms and has a low battery cut off around 6v as batteries will be in series. if it's a bit more say 6.4v you can up the resistence range below. It should detail somewhere what the low battery cut off is.

If your are vaping around 75w

Square root of power (wattage) x resistence will give you the Voltage

75 x 0.5 = 37.5 and it's square root = 6.12v

So if you want to get the longest time out of the batteries you are using build between 0.1 and 0.5 ohms

Works differently on a mechanical device so don't apply this for that

Are you using decent batteries.... Samsung 25R/ 30q, Sony VTC6 for instance?

Currently I have lg 21865 32a my build is dual 28g claptons 8 wraps .83 ohms I change from 65 to 70 watts today 7.37 volts the flavor is so crisp it's like I'm drinking the juice a very cool vape the vapor is exceptional 70/30 blend my battery has lasted all day definitely a flavor build with clouds.I build to I find my liking this is one of my favorites so far.The bottom air chambers makes this build by far.

 

[Locomotion]

3mm diameter

 

[KingPin!]

If variable wattage is used, resistance has absolutely nothing to do with battery drain rate. You’re passing bad info.

Didn't say battery current drain did I....I said how quickly the low battery warning message kicks in ...the mod still detects the resistence of the atty and tries to fire it and will continue to do so until it can't anymore due to capacity reserves that is linked to what I said

 

[BoomStick]

Yeah, because battery current has no relation to voltage sag. Whatever. Good luck.

 

[KingPin!]

Yeah, because battery current has no relation to voltage say. Whatever. Good luck.

What? Ok your gonna have to stop writing two sentences here I'm not a mind reader so being you believe I've given such bad information how about you explain obviously the "proper way"and see if what you come up with is different to what I said

Or just continue to offer nothing other than knocking my input

 

[BoomStick]

Voltage ‘sag’. Auto incorrect.

 

[KingPin!]

Actually to save you some time boomstick here's is a post where you explain it

http://vapingunderground.com/thread...s-on-battery-drain-rate-regulated-mod.277628/

I would still say though whenever I've used a VW mod and use the equation above against a build I've got in the atty the voltage output displayed on the mod matches what I'd calculate manually above (voltage wise) ....and when the mod can no longer output that voltage it displays low battery message

So this you are saying isn't what's happening?

 

[BoomStick]

So to offer something more to the op, lower resistance builds usually require more power because they have more wire mass that needs heated, not because their resistance is lower. And in short, if you want your batteries to last longer then turn down the power. Might need less coil mass to still allow for the vape you’re looking for. Build resistance has nothing to do with battery current when using a variable wattage mod. Only watt setting. The higher the setting, the more power you pull from the batteries, the faster they drain.

 

[BoomStick]

I understand that the mod will shutoff when the voltage of the batteries gets below a certain number. It’s my opinion that trying to squeeze a few extra vapes out of batteries by building to a certain resistance is a waste of time if it even matters. If the op wants longer runtime I suggest a build with lower coil mass as it will require less power. If he was trying to push the limits of the mod he needs to be in a small resistance window. Vaping a dual batt mod at 70’ish watts allows a bigger window and I suggest he worry more about coil geometry than hitting some specific resistance.

 

[BoomStick]

And honestly, I don’t see how build resistance has anything to do with when the mod cuts off. If the chip needs “x” watts, the resistance of the build has nothing to do with the combination of volts and amps required from the batteries to make “x” watts. You could change the build to whatever, but if the watt setting stays the same, the battery voltage and required amps needed to supply those watts doesn’t change.

 

[KingPin!]

I've always believed the voltage output on a regulated mod changes proportional to the resistence build you use and the power selected, hence why on some mods if you build above a certain resistence say 0.5 and try to hit 220w the mod will either try to limit the wattage you can select or just taper down the voltage automatically based on the max voltage output the chip allows (say 6v on a lot of dual battery boards).

And when that voltage output is higher than the chips low voltage cuff off setting (because the batteries no longer have the voltage left to input and maintain that wattage setting) it will no longer fire.

 

[f1r3b1rd]

And honestly, I don’t see how build resistance has anything to do with when the mod cuts off. If the chip needs “x” watts, the resistance of the build has nothing to do with the combination of volts and amps required from the batteries to make “x” watts. You could change the build to whatever, but if the watt setting stays the same, the battery voltage and required amps needed to supply those watts doesn’t change.

Forgive my intrusion, but I'm a little confused by what you're saying here.
Can you explain it a little more?

 

[BoomStick]

I've always believed the voltage output on a regulated mod changes proportional to the resistence build you use and the power selected, hence why on some mods if you build above a certain resistence say 0.5 and try to hit 220w the mod will either try to limit the wattage you can select or just taper down the voltage automatically based on the max voltage output the chip allows (say 6v on a lot of dual battery boards).

And when that voltage output is higher than the chips low voltage cuff off setting (because the batteries no longer have the voltage left to input and maintain that wattage setting) it will no longer fire.

Paragraph 1. Yes. Output voltage is limited so the resistance range is limited if you want to max the watt output.

Paragraph 2. Output voltage and input voltage are 2 different things. What you’re saying could be an issue if there is no boost circuit. If the mod can only buck it down, but not boost it up, then I say you’re right. However, if output is limited to 6v and input shuts off at 3.2v per cell (common limits for dual batt mods) it’s not an issue. In that case the only way to increase runtime is turn down the watts.

 

[KingPin!]

Paragraph 1. Yes. Output voltage is limited so the resistance range is limited if you want to max the watt output.

Paragraph 2. Output voltage and input voltage are 2 different things. What you’re saying could be an issue if there is no boost circuit. If the mod can only buck it down, but not boost it up, then I say you’re right. However, if output is limited to 6v and input shuts off at 3.2v per cell (common limits for dual batt mods) it’s not an issue. In that case the only way to increase runtime is turn down the watts.

I feel we are working towards a common answer here can you run through a few working examples boomstick? Include the workings so I can how you are claulting it I'm still scratching my head here with the responses if I'm honest, if it helps here is some example data to work with


Say the mod is VW
200W series dual battery
Boost or Buck (if answer is different run through both)
Chip efficiency is 95%
Low voltage cut off is 3v (nice round number includes sag)
I have a 0.15 Ohm coil in the atty
I want to vape at 100W
Max output voltage 8.4v (what I meant to say above not 6 sorry)
Max board output Amp limit is 50A

This is all the information you have to hand

Here are my workings:

Input circuit I calculate 17.54 max amp draw at low cut off

100 / 2 / 3 /0.95 = 17.54A

Output circuit I calculate 3.87v (using my formula further up above)

Sqrt 100 x 0.15 = 3.87V

So when my batteries can no longer service that 3.87v it shuts off

How do you approach this?

 

[Locomotion]

I'm blowing clouds watching you two go back and forth.Its not that serious just personal preference.Here's a dumb question but I'm going to ask anyway.The term too low in ohms give me an example. .1 I'm claiming as 10 ohms or is it after .99 as 1. Ohms if .99 is to low then explain

 

[BoomStick]

dc to dc converters can exchange volts for amps and vice versa. The chip doesn’t give a crap what the output volts or amps are (within its range of course), it only cares what the total output total power is when determining what to draw from the batteries. The watts. If 100 watts are needed on the output side, it pulls 100 watts from the batteries, then converts the input volts and amps to what it needs to output to the coil resistance in order to make 100 watts. The amps it pulls depends on the battery voltage. As voltage drops, current increases. Once the voltage of the batteries under load drops below the programmed low volt cutoff, it cuts off. Changing resistance causes a different combination of voltage and amperage to be output, but the total output power doesn’t change so it doesn’t change the power required from the batteries.

 

[The Cromwell]

I'm blowing clouds watching you two go back and forth.Its not that serious just personal preference.Here's a dumb question but I'm going to ask anyway.The term too low in ohms give me an example. .1 I'm claiming as 10 ohms or is it after .99 as 1. Ohms if .99 is to low then explain

Ohms is just like any number the lower the value the lower the ohms.
The higher the value the higher the ohms.

 

[KingPin!]

dc to dc converters can exchange volts for amps and vice versa. The chip doesn’t give a crap what the output volts or amps are (within its range of course), it only cares what the total output total power is when determining what to draw from the batteries. The watts. If 100 watts are needed on the output side, it pulls 100 watts from the batteries, then converts the input volts and amps to what it needs to output to the coil resistance in order to make 100 watts. The amps it pulls depends on the battery voltage. As voltage drops, current increases. Once the voltage of the batteries under load drops below the programmed low volt cutoff, it cuts off. Changing resistance causes a different combination of voltage and amperage to be output, but the total output power doesn’t change so it doesn’t change the power required from the batteries.

Thanks Boomstick ....reading this response goes along with what I posted above in my example run through a few posts above?

Either way looks like I need to do some further reading to understand it fully. If it turns out what I'm saying is bollocks I'll happily edit it and other material I've posted as well but without any workings shown I can't just change my stance for now.

 

[BoomStick]

I don’t know what you want. Before you can apply numbers to something, you have to understand the concept. I’ll state it again. Build resistance has nothing to do with what’s going on with the input side of the chip. Only watt setting does. Don’t believe me? Check steam engine. The runtime tab shows you can change resistance to whatever you want and runtime stays the same if watt setting doesn’t change.

 

[The Cromwell]

If you violate ohms law bad things can happen in vaping.

 

[KingPin!]

I don’t know what you want. Before you can apply numbers to something, you have to understand the concept. I’ll state it again. Build resistance has nothing to do with what’s going on with the input side of the chip. Only watt setting does. Don’t believe me? Check steam engine. The runtime tab shows you can change resistance to whatever you want and runtime stays the same if watt setting doesn’t change.

It's not I don't believe you boomstick I'm just not familiar with everything you are saying and I freely admit I need to learn more about the converters I have no problem admitting that.

I did go and check out the battery page as you say and agree it didn't affect run time changing the resistence. Perhaps the bit I'm getting hung up on is the notes below that calculator, they seem to follow parts I posted ....at least in my example posted in terms of input and output calculations but the run time does appear to be different so I need to understand how to work that part out and go through the theory ....


Source steam engine....
http://www.steam-engine.org/batt.html

"Regulated mods – fixed or variable voltage or power
Regulated mods are more difficult to model. But even though they are much more complex than mechs, with some selective simplification we can safely ignore most of the complexity. So we break these mods down into two circuits and a black box. This makes our regulated mod model little more than twice as complex as our mech mod model.

The two main circuits of a regulated mod are:

• The atomizer (output) side.
• The battery (input) side.

And never the twain shall meet. The regulator circuit takes care of that. It can have a bunch of more or less advanced circuits in itself, and it uses a little bit of power, but for the most part we can envision it as a black box separating the battery circuit from the atty circuit.

Tread carefully – here be pitfalls
Since we are looking at two separate circuits, you can never mix numbers from both sides of the regulator in your calculations. For instance: You cannot determine the current drained from the battery by measuring the resistance of the coil and the voltage of the battery. Using the resistance from one circuit, and the voltage from a different circuit, will result in a nonsensical answer. Nor can you determine the current going through the coil by determining the current from the battery.

Output – the atomizer
On the atomizer side, the voltage is ideally whatever the user has selected, but keep in mind that some APVs promise more than they keep. If you set the voltage to 5V, are you confident that the APV actually delivers 5V? Unless you know that your APV is accurate, you might want to measure and confirm the output voltage under load.

Variable wattage devices work like variable voltage devices, for the most part. The difference is that they measure the atomizer resistance, and uses this measurement, and Ohm's law, to calculate what voltage to set in order to reach your desired power.

Likewise, knowing the output voltage and resistance, you can calculate the output current and power yourself.

Input – the battery
On the battery side, the voltage is whatever the battery has in it at the moment, just like with mech mods. The power, however, is whatever the regulator needs to pull in order to deliver the desired voltage to the atomizer at any given time. So by dividing the power by the (ever decreasing) battery voltage, we find the (ever increasing) current.

Transfer the power – getting down to it
So how can our measured resistance tell us anything about battery drain? Well, there is one way to "transfer information" from one side of the regulator to the other. The trick is simple; to paraphrase some old movie: Use the power, Luke!

The power hitting the atomizer equals the power flowing from the battery, minus the power used by the regulator circuit.

These regulator circuits typically boast an efficiency between 80–95%. In practice this means that the regulator "steals" about a tenth of the power from the battery.

Knowing this, we can use our multimeter and Ohm's law to calculate what is going on at either side of the regulator. Then we can convert it to Watts, and voila! Subtracting (or adding) the loss in the regulator circuit, we now know the power on the other side as well.

Lastly, we use Ohm's law again, break down the power to current and voltage, and that's that: We now have all the numbers we need."