Eureka! Volts, Ohms and Watts 101

[OneDay]

Apologies in advance for this long post, but I hope it’s worth it. During the time I’ve been vaping I have been confused by the whole Volts / Ohms thing ???. From the number of posts and questions I know it’s a subject that confuses many others too. This isn’t helped by all the choices and abbreviations. Standard Resistance (SR) – standard to what? By whose definition? Low Resistance (LR) – Lower than what? How low is too low? If 2.0 is low, what the heck is 1.5? And now we’re all able to get into Variable Voltage, especially now the Twists are here, it can become a nightmare. Various people have answered these questions on threads but I found the answers as confusing as the questions as I’m not a scientist and have forgotten whatever physics I learned at school

Someone posted a chart a few days back that I’ve seen a few times before, and I kinda yawned… charts remind me of work or school. I had another look at it and suddenly the penny dropped. Finally the whole thing made sense

So, I’m going to try to explain my understanding in the clearest way I can in the hope that it may help somebody else. If anyone with a technical mind finds that I have, in fact, completely MISunderstood, let me know! OK here we go….

In any e-cig, from a disposable to a provari, all that is happening is that a battery is passing a current through a coil of wire, causing it to heat up. That’s what happens in a light bulb. The current heats a coil until it glows white-hot. Now we don’t talk about Ohms of light bulbs, we don’t worry what Voltage our mains is. We buy based on Wattage. We know that a 100 watt bulb burns brighter than a 60 watt bulb. Simples. And it’s the same with vaping. When people talk about finding the ‘sweet spot’ what they mean is that for a particular juice you’ve found the wattage (i.e. the heat) that suits it best, makes it taste best or vape best. It’s like finding that a particular wattage bulb is best for reading, or another is best for watching telly. With me so far?

OK, back to that chart. This shows volts along the top and ohms down the side. But all the numbers in the middle are watts. You can see that they have highlighted a cell in the middle (the pink one) that shows 6.45 watts. By reading up and sideways from this cell you can see that the 6.45 was achieved by a combination of 4.75 volts (at the top) and 3.5 ohms (at the side).



Now, here’s the clever bit. Let’s say you have a 3.5 ohm carto or clearo or whatever, and you find that using it at 4.75 volts gives you your sweet spot. In other words, you prefer to vape this juice at 6.45 watts. One day your 3.5 carto dies and it was the only one you had. How can you achieve that same delicious vape? Well, if you look at the chart again you can see that the magical 6.45 watts, or numbers damn close, can be achieved in different ways which I’ve circled. So, you could use a 2.8 clearo at 4.25 volts, or a 1.8 at 3.4 volts, or even a 1.5 at 3.0 and a bit volts and they will all give you more or less the same vaping experience.



Phew. Now I know what to use in my vaping kit, what to pair with what, and why some vaping combinations taste better (or worse) than others. Hallelujah

[Batdragon (AKA Batty)]

This is the first attempt at the Sweet Spot power calcs spreadsheet.

It is in Excel 2007. If you have any issues, problems or spot any mistakes, please get back to me to fix

Attachments:

[Batdragon (AKA Batty)]

Excel 2003 version

Attachments:

[Batdragon (AKA Batty)]

Ok these are the alterations so far

1. Reduce decimal places to one place on first sheet. (What about the table, should I do the same there?)
2. Put in a check sum for the device's maximum amps capability
3. Put in another column in the notes sheet so that Watts can be recorded.

Oneday, if both the resistance, voltage & watts are recorded on the notes sheet, you could just put the figures back into the first sheet to get the table to highlight the group of possible combinations. Was this wat you were meaning?

I think I might have gone too far with the resistance values. What are the highest and lowest values that are available?

Got some work to do on this, though once done perhaps one of the mod's could put it in a "Useful download area" for everyone to find easily

[2risky]

It's reasonably simple for dual coils/resistors in parallel, especially if the 2 coils are identical.

Generally, for resistors R1, R2 in parallel
Total Resistance = (R1 x R2) / (R1 + R2)

don't pull faces, it's primary level arithmetic!

Where R1 = R2, eg most dual coils
Total Res = (R1xR1)/(2xR1)

Power and current calculations are the same, only you replace the single coil resistance with the total parallel resistance.

Sorry, I can't help it.

[FirinBlanks]

Here you go Chaps and Chapesses

Firin's patented rotary wattage miraculum v1.

Or in plain old English... a spreadsheet wot I dun.

If you'd like any changes made, please feel free to go ahead

Attachments:

[robby]

This is a useful online calculater for ohms/watts/current/volts. Input any two values and it will work out the other two, so it can tell you if something is practical or not,

ie. it can tell you if a certain combination is going to require too much current, or is gonna suck your battery dry very quickly by burning too many watts etc


www.bowdenshobbycircuits.info/ohmslaw.htm

[Deleted]

I use the pv tuning tool on the ejuice calculator. Simply enter your atty resistance and preferred vaping wattage, press calculate and up pops the relevant voltage setting - simples.   Download available here ejuice.breaktru.com/

[davetherayon]

Here is a neat list of several battery types with on the right the minimum safe coil resistance : so for an AW IMR 18490, 0.5 gnomes.

It's important you get your batteries from a reputable source, spend a little more and don't have it explode in your hand!