could anybody help on dumbing down the ohm's law for me please? I've been building my own coils on rda's for months now, just basic 8wraps of 24g kanthal at 0.2ohms (sometimes 1.9) and use it at 60watts but never really took notice to the ohms law though, I'm clued up about battery safety so never really been worried about my builds. I feel like I'm getting bored of my builds now and fancy a change and want to know what is safe and not. Sorry it's abit long winded, I'm looking on internet for sub ohm law but i just don't understand it. Is it me being thick or are the graphs hard to grasp?
Ohm's law...
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This implies to me that you're using a regulated VW or "variable-wattage" device. Ohm's law is more important on an unregulated, mechanical mod. Ohm's law states that the current (amperage) through an electrical conductor between two points is directly proportional to the voltage, and inversely proportional to the resistance (ohms). The equation is as follows:
I = V/R, where I = current, V = voltage, and R = resistance.
This says that Amps = Volts / Ohms. The power equation (sometimes referred to as "Watt's Law") is a related concept, which states that power (wattage) is directly proportional to the square of the voltage, and still, like with the amps, inversely proportional to the resistance:
P = V^2 / R, or Watts = Volts * Volts / Ohms.
As these are mathematical equations, you can rearrange the terms and they will still hold true. For example, Ohm's law (I=V/R) could also be stated as V=IR or R=V/I. It just depends on which are the knowns, and which are the unknowns.
Ohm's law is important in a mechanical mod because it tells you how many amps you are drawing from the battery. Try to pull too many amps, and the battery goes *BANG!* (Or, more likely, it goes "pfffFFFFFFFTSSSSSSSSSSSSSSSHHHHHHHH" as it vents hot gases and flames -- it's not likely to actually explode unless it's confined inside a rigid container like a metal tube without adequate venting, aka certain mechanical mods that do not have vent holes. Regulated devices too, I guess. Anything with a battery in it should have adequate venting, even your laptop and cell phone use the same kind of batteries we use and can vent if abused.) Ohm's law calculations should always be done assuming 4.2v, as with a fully-charged battery.
With a mechanical mod, the battery voltage is applied directly to the atomizer, and so the wattage (and amperage) will vary along with the battery charge state. With a regulated device, however, the wattage is held constant by the circuitry inside. Let's take another look at Watt's Law:
Watts = Volts * Volts / Ohms
Note that "volts / ohms" makes up a part of the equation. But "volts / ohms" is also equal to another value we have already discussed, the current (amps). So you could also state it as Watts = Volts * Amps. If you know the watts (determined by user setting) and volts (battery charge state), but not the amps, just divide both sides by volts to end up with Amps = Watts / Volts. If your device is set at 60 watts, for example, and the battery has 3.7v charge remaining, then you are drawing 60 / 3.7 = 16.216 amps. Note that I didn't mention ohms. That's because ohms don't matter on a wattage-regulated device. All that matters are the wattage setting, and the battery charge state. If your battery can safely push 60 watts, then it doesn't matter if it's pushing them through two ohms, or two-tenths of an ohm -- the amp draw is the same in either case. Since the amp draw is highest on a weak battery (as opposed to a mechanical mod, where it is highest when the battery is at full charge), Watt's law calculations should always be done assuming 3.2v or whatever the low-voltage cutoff is on your particular device, since that's when the battery will be worked the hardest at a given wattage setting.
Note that we are talking about the output voltage (charge state) of the battery which is often represented only by a "fuel gauge"-type icon on the device's interface, and not the applied voltage delivered to the atomizer, which may be displayed as a numerical value. These are not the same value (not usually, anyway, but even a broken clock is right twice a day.) If you want to know the output voltage more precisely than "well it looks to be about two-thirds full, or so" then you will need to check it with a multimeter. Some chargers, and a few (but not very many) devices also show the battery voltage as a number, but usually it's just the not-very-precise battery bar on the device, or a blinking red/green light on the charger.
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...long story short ["too late!", cries the peanut gallery], Ohm's law is for mechs. If your regulated device can fire a coil, it will fire it, and if it can't, it won't; don't worry too much about the ohms except making sure they are within spec. Just make sure you don't push more watts (on any coil) than your battery can handle.
Ohm's law | Steam Engine | free vaping calculators
the idea is to build coils to stay within your battery's amp limit headroom per given wattage..............
You don't need to worry about Ohm's law on a regulated mod. But if you still want to calculate the amperage your battery is pushing, you simply solve the following equation:
I = P/V
Where:
I = the amperage
P = power in watts
V = battery voltage
So, if you're running your mod at 60 watts on a battery charged to 3.7v, then:
I = 60/3.7
I = 16.2A
On regulated mods, it is watts in and watts out. The coil resistance makes no difference.
I = P/V
Where:
I = the amperage
P = power in watts
V = battery voltage
So, if you're running your mod at 60 watts on a battery charged to 3.7v, then:
I = 60/3.7
I = 16.2A
On regulated mods, it is watts in and watts out. The coil resistance makes no difference.
Thank you all, much appreciated! Oh right so it's more for the mech mods? I don't intend on ever getting 1 of those, but suppose the ohms law is still good to know.
Ohms's law is good to know, but it can lead you wrong when using variable wattage mods. For calculating battery amp draw with those I suggest you use the Steam Engine battery drain calculator. Use 3.2V of a single battery and 6.4V for dual batts.
It also works very well for VV mods, just make sure that is what you've selected.
Does this apply to the coil builds in heads for tanks as well? Like how a .3 coil is recommended used between 70-80W, would you be able to crank it to, say 100w on a vv/vw mod?
What's the internal diameter of your coils?
I only ask is it's strange to hear about 8 wraps of 24g reading 0.2 ohms, unless you're build has a 1mm internal diameter and is dual coil?
Dual Coil, 8 wraps, 24g, 1mm ID, 0.2 Ohms
This is as simple as it gets if you're just worried about how many amps you're drawing.. Just enter your ohm's and watts and it will tell you the rest.
Watts/Volts/Amps/Ohms conversion calculator
0.2 @ 80 watts would be a 20amp draw, which is the limit for most batteries, I build lowest 0.3 to keep it below max..
Watts/Volts/Amps/Ohms conversion calculator
0.2 @ 80 watts would be a 20amp draw, which is the limit for most batteries, I build lowest 0.3 to keep it below max..
Good advise. I use dual battery and Lipo Mods to keep the Amps in check.
In my tool kit it doesn't say the diameter on the coil jig but it's definitely not 1mm, i'd say its about 3-4mm and yes it is a duel coil build. My coil master v2 is being delivered saturday so i can know exactly what I'm building, if i knew how to post pics on here i'd try show you.
I thought about buying one of those little boxes that tells you what ohms your installed coil build is (ie: Coil Master) .... but I am convinced that a good quality multimeter is more accurate (and I already have a Fluke multimeter, so why go buy one of those little coil boxes that are made specifically to read the coil ohms .... just my opinion
Here is what I use:
Here is what I use:
Is there going to be a test at the end?
Getting along in years and a bit forgetful. However:
I can read charts and graphs.
and Apps for Saps
Use multi-meters and readers.
Follow manufacturers Specs. on everything from Regulated mods to Batteries and just about anything else I've ever owned.
Getting along in years and a bit forgetful. However:
I can read charts and graphs.
and Apps for Saps
Use multi-meters and readers.
Follow manufacturers Specs. on everything from Regulated mods to Batteries and just about anything else I've ever owned.
I'm curious to know what 2900mAh batteries you're using, too. The only ones that I am aware of are from Panasonic:
Panasonic NCR18650PF (LiNiCOMnO2) 2900mAh 10A CDR
Panasonic NCR18650PD (LiNiCoAl) 2900mAh 10A CDR
Note that both batteries are only 10 amps continuous discharge rate. Orbtronics also rewraps these Panasonic cells under their own brand name.Panasonic NCR18650PD (LiNiCoAl) 2900mAh 10A CDR
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