Don't forget about Watts Law

[Dlmdavid]

http://teched.gpvanier.ca/electronics/electronics11/theory/Ohms and Watts Laws - presentation.pdf

Here's a great site that explains things a lot better than I can, just skip all the stuff on kirchhoffs law

 

[Lessifer]

So... To determine what batteries you need,

Variable wattage mod:
Max watts/battery cutoff voltage/number of batteries

Mech mod:
Max voltage/target coil resistance

I assume a fixed voltage battery, like an old ego would be like a mech. What about a true variable voltage, like a spinner/twist?

 

[Dlmdavid]

So... To determine what batteries you need,

Variable wattage mod:
Max watts/battery cutoff voltage/number of batteries

Mech mod:
Max voltage/target coil resistance

I assume a fixed voltage battery, like an old ego would be like a mech. What about a true variable voltage, like a spinner/twist?

I have no experience with them, but are they not built in batteries with certain resistance firing ranges? If so its not something to ever be concerned about

 

[sparkky1]

I agree with most of what you're saying, as far as you never using watts law, that is fine, in my career as an electrician it is something that has come up often both by professors and through textbooks, and a term I use on the job quite often. Your power formulas are my watts law, I'm not really sure how this thread turned so ugly, my entire point of starting it was more or less to say current draw on a battery is measured by P/E in a regulated mod and E/R in a mech mod, I've had so many people tell me they calculate how much current in their regulated mods by E/R because the guy at the vape shop told them they needed to use ohms law. That kind of vague information is what's leading to people having their batteries vent and explode and it's a huge pet peeve of mine

Think PLC's sparky (if you've ever worked with them). still needs a switch of some kind to regulate (PFM) buck boost TC, it's not a flashlight switch ....................

 

[Lessifer]

I have no experience with them, but are they not built in batteries with certain resistance firing ranges? If so its not something to ever be concerned about

well, you should be concerned with not trying to fire too low of a resistance coil, so as not to pull more amps than the battery can handle, like a mech, right? I think most have built in cutoffs, but there are plenty of cheap vv stick batteries out there and I'm sure at least some of them will fire something lower than it should.

 

[mauricem00]

Actually what you're referencing is watts law, ohms law is the relationship between voltage, current, and resistance. Watts law is the relation ship between voltage, current, and power. Telling an inexperienced vaper to learn ohms law will have them assuming resistance is what matters in every case. If I put a .3 ohm coil on my Sigelei and run it at 50w, I'm gonna draw the exact same current as a 1 ohm coil at 50w assuming the voltage on my batteries stays constant. Since I don't use mech mods I've never once had to refer to ohms law, I just worry that most people saying "get a good understanding of ohms law" are only saying it because that's what they were told when they started vaping, if they don't know the difference between ohms law and watts law it tells me they don't actually have a good understanding of ohms law.

since reaching 50 watts on a .3 ohm coil would require 3.87 volt from the battery plus the voltage drop of the regulator circuit the current drain from the battery would be the same as 1 ohm under 50 watts.regardless of of what kind of mod we are using.current drain from the battery is the primary concern.the coil current would be different but not the battery current and too much current thru the coil would simply cause it to overheat and give a hot vape till the coil opened like a fuse. I prefer operating my sigelei over 4.5 volt output and build coils accordingly. but knowing ohms law includes knowing how the design coils for the power level you want to vape at

 

[Dlmdavid]

Think PLC's sparky (if you've ever worked with them). still needs a switch of some kind to regulate (PFM) buck boost TC, it's not a flashlight switch ....................

Yes I know but it still doesn't change anything, I've always considered them like a type of VFD but the batteries still don't see the resistance of the coil.

 

[Lessifer]

I know that VW mods are very popular right now, but there are plenty of vapers who still use ego type batteries, and plenty of mech users. So let's just say a well rounded vaper should know both, and which one to apply to their mod of choice.

 

[Dlmdavid]

I know that VW mods are very popular right now, but there are plenty of vapers who still use ego type batteries, and plenty of mech users. So let's just say a well rounded vaper should know both, and which one to apply to their mod of choice.

Yes absolutely, I'm not saying forget ohms law, just need to educate on more than just calculating based on resistance

 

[Lessifer]

Yes absolutely, I'm not saying forget ohms law, just need to educate on more than just calculating based on resistance

Yup, I learned something from this thread I did not know before, thanks for that

I probably won't ever use it myself, but it's a good bit of knowledge to have.

 

[sparkky1]

Yes I know but it still doesn't change anything, I've always considered them like a type of VFD but the batteries still don't see the resistance of the coil.

No they do not, that's the difference in DC, sort of, the (switch) looks, at the amp draw and NOT the load from the atty .....................

 

[Dlmdavid]

No they do not, that's the difference in DC, sort of, the (switch) looks, at the amp draw and NOT the load from the atty .....................

Yes that's what I've been trying to say, I'm not sure if we're at an agreement or disagreement here...

 

[sparkky1]

Yes that's what I've been trying to say, I'm not sure if we're at an agreement or disagreement here...

I'm an electrical contractor, I build PLC's for major manufactures around the world, so what do you think ?

 

[Dlmdavid]

I don't know what you're getting at

 

[Ryedan]

Wow this thread is amazing me, it really is not as complicated as people are making it, if you put a wattmeter across a coil and set it to 50 watts you will read 50 watts, the coil is a fixed pure ohmic resistance, there is no magnetism involved or any other type of opposition to current flow, current will travel through the coil creating power that will be dissipated as heat, no questioning it. Energy can not be created or destroyed, you're using the energy from your battery and converting it to heat, it's really not that hard to understand. Any other type of energy loss would be negligible.

Thank you Dlmdavid, you've hit the proverbial nail on the head

 

[Ryedan]

This is the example of coils that are actually different. However, Surface Area -- or simply how "big" the coil is -- is only one factor determining maximum power. Each factor is a limit, increasing one doesn't help without the other. In fact, everything being sort of matched results in the best vape.

Yes the coils were different, but they vaped almost the same at the same power level. That was my point

 

[jbnuke]

Threads like this entertain me... lol i build my coils to a minimum of .2 ohms. No reason to build lower with a vw mod. Usually i sit around .4. With 2 and 3 battery vw mods all using 25r's, no, no im not worried about ohms law or watts law or any other law because i am building where i know i am safe. Simple as that.

 

[David Wolf]

I agree with most of what you're saying, as far as you never using watts law, that is fine, in my career as an electrician it is something that has come up often both by professors and through textbooks, and a term I use on the job quite often. Your power formulas are my watts law, I'm not really sure how this thread turned so ugly, my entire point of starting it was more or less to say current draw on a battery is measured by P/E in a regulated mod and E/R in a mech mod, I've had so many people tell me they calculate how much current in their regulated mods by E/R because the guy at the vape shop told them they needed to use ohms law. That kind of vague information is what's leading to people having their batteries vent and explode and it's a huge pet peeve of mine

Hey I owe you an apology for not acknowledging your point was valid, I was just addressing the term I've not seen used in electrical engineering. Some good discussions and I stayed out of the math talk because it's the weekend and I don't so math on weekends haha

 

[sonicbomb]

Threads like this entertain me... lol i build my coils to a minimum of .2 ohms. No reason to build lower with a vw mod. Usually i sit around .4. With 2 and 3 battery vw mods all using 25r's, no, no im not worried about ohms law or watts law or any other law because i am building where i know i am safe. Simple as that.

On a VW device the resistance is irrelevant. If you don't know how many amps you are pulling from your batteries, how do you know you are safe? On your 2 cell mod with those 25Rs once you hit 150W, you are right on the edge of their CDR. I'm not saying your setup is safe or not, the point is you should know how to work that out.
This just shows what mess this thread has become.

 

[jbnuke]

Well lets see here you do a quick calculation to see if your batteries can handle the max current your mod can push and if they can... done... no ohms law watts law civil law criminal law.
Or even easier, check on like here and look at what mods people are using with what batteries. Im just saying the vast majority of the worry people have about exploding mods are
1. Mech mods improperly setup
2. Batteries not meant for vaping.
And..... better chance of getting killed in a car wreck than having a mod blow up in your face...
Yes safety is important. But there is no need to know all these laws by heart.