I know it's basically a regulated mod with a POT for VV rather than buttons for VW, but I'm still not quite sure how one would go about calculating amp draw. If it does work like any old regulated mod, would that mean that I'd need to use the set voltage and resistance to calculate wattage and use the wattage to determine how much current is coming from the batteries?
Calculating amp draw on Hexohm 3.0?
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I'm familiar with Ohm's Law, and it would only tell me the current going to the coil. In a regulated mod that's not the same as the current drawn from the battery. I'm trying to figure out whether to treat the Hex as a mech or a regulated mod when calculating current FROM THE BATTERIES.
Mmmkay, drives the coil with a DC/DC converter and you tune up the voltage, so:
PCOIL / efficiencyDCconv = PBATT
As P = V × I,
(VCOIL × ICOIL) / efficiencyDCconv = VBATT × IBATT => ((VCOIL × ICOIL) / efficiencyDCconv) / VBATT = IBATT
As I = V / R,
IBATT = ((VCOIL² / RCOIL) / efficiencyDCconv) / VBATT
Example for a 0.2Ω load (coil resistance), 4V output selected in the mod, efficiencyDCconv at 90% and source (battery) down to 3V (almost empty):
IBATT = ((16 / 0.2) / 0.9) / 3 = 29.62963A (peak)
Cheers
PCOIL / efficiencyDCconv = PBATT
As P = V × I,
(VCOIL × ICOIL) / efficiencyDCconv = VBATT × IBATT => ((VCOIL × ICOIL) / efficiencyDCconv) / VBATT = IBATT
As I = V / R,
IBATT = ((VCOIL² / RCOIL) / efficiencyDCconv) / VBATT
Example for a 0.2Ω load (coil resistance), 4V output selected in the mod, efficiencyDCconv at 90% and source (battery) down to 3V (almost empty):
IBATT = ((16 / 0.2) / 0.9) / 3 = 29.62963A (peak)
Cheers
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Mmm, just for the sake of completeness: please don't overestimate battery output voltages, they're largely affected by the current load through them. All of the battery voltage drops in the circuit, but the load only “sees” the remaining part after what is lost heating the battery innards because of its internal resistance.
So please, select “low” VBATT values (VLOAD = VUNLOADED - I × RBATT).
Cheers
So please, select “low” VBATT values (VLOAD = VUNLOADED - I × RBATT).
Cheers
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Thank you, kind sir. This is exactly what I was looking for, if a little on the complicated side. I need to exercise the ol' noodle anyway. 
In what way would all these maths be affected by the fact that the Hex runs a pair of 18650s in series?
The end result is essentially cut in half. Each cell is responsible for half of the total current.
If the batteries are in series, VBATT doubles (Darth Omerta is on track).
Another example for a 0.15Ω coil, 5V at the coil and everything else the same (efficiencyDCconv = 90%, 6V at the battery -2 cells × 3V/cell-):
IBATT = ((VCOIL² / RCOIL) / efficiencyDCconv) / VBATT
IBATT = ((25 / 0.15) / 0.9) / 6 = 30.864197530864A peak
For the previous coil values:
IBATT = ((16 / 0.2) / 0.9) / 6 = 14.814815A peak
Cheers
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For the sake of completeness 2nd edition:
The values obtained with that equation,
IBATT = ((VCOIL² / RCOIL) / efficiencyDCDC) / VBATT
… can be used as a guideline for choosing the right cells for your mod/setup.
In the above examples, for the 30.864197530864A I'd go no less than VTC5As, HB6s if you want to stay completely safe.
For 14.814815A, HG2s, 30Qs, VTC6s, or anything above 15A continuous rated cells, good for 26650 setups as the market for 15+A CDR cells is more limited (though there are quite good cells fairly priced now).
Cheers
The values obtained with that equation,
IBATT = ((VCOIL² / RCOIL) / efficiencyDCDC) / VBATT
… can be used as a guideline for choosing the right cells for your mod/setup.
In the above examples, for the 30.864197530864A I'd go no less than VTC5As, HB6s if you want to stay completely safe.
For 14.814815A, HG2s, 30Qs, VTC6s, or anything above 15A continuous rated cells, good for 26650 setups as the market for 15+A CDR cells is more limited (though there are quite good cells fairly priced now).
Cheers
Vcoil = √(Wcoil × Rcoil) => V = √(80 × 0.15) = ≈3.464V at the coil for 80W
Pretty easy to handle (close to 90W including the DC-DC converter overhead) for a couple of VTC5As. This means longer life for your cells.
Pretty easy to handle (close to 90W including the DC-DC converter overhead) for a couple of VTC5As. This means longer life for your cells.
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Just edited the aforementioned expression, it's basically all you need as long as you think in power delivery terms:
Vcoil = √(Wcoil × Rcoil)
Select target coil power Wcoil and coil resistance Rcoil, that expression gives you the desired coil voltage to tune.
Power at the coil is served by the DC-DC converter, so Wcoil = Wbatt / efficiencyDCDC, which means you need slightly more total power from the cells, yet with a couple VTC5As you can safely go up to ≈150-160W at the coil (this means current from the cells will go a bit above the maximum continuous rating but only at the very end of the battery discharge, so no time enough to get even remotely close to an overheat condition anyway).
Cheers
Vcoil = √(Wcoil × Rcoil)
Select target coil power Wcoil and coil resistance Rcoil, that expression gives you the desired coil voltage to tune.
Power at the coil is served by the DC-DC converter, so Wcoil = Wbatt / efficiencyDCDC, which means you need slightly more total power from the cells, yet with a couple VTC5As you can safely go up to ≈150-160W at the coil (this means current from the cells will go a bit above the maximum continuous rating but only at the very end of the battery discharge, so no time enough to get even remotely close to an overheat condition anyway).
Cheers
Here's a simple equation that has worked well for me...
Calculating battery current draw for a regulated mod | E-Cigarette Forum
Well hey there mooch i was the guy in Juicy Jones live show and asked about the .15 aliens on my hexohm 3.0 with the vtc 5A's thank you for the reply!
So going by your post im wanting to run a set of nicrome aliens (.15) on my hexohm 3.0. Married VTC5A's
I want to get 85-90w safely.
90/2=45 per battery
45/3= 15amps per battery
So about 3.64x3.64=13.2496/.15= about 88w am i correct?
I can't verify everyone's math but if you follow the equation you'll be ok. Add 10% to the current for worst case regulator efficiency.
Barkuti is just using some nice ohms law equations to achieve a meaningful result. It's the variables with subscript annotations that make it look complex. Once you figure out how to interpret the equations they make perfect sense.
You can play around with Steam Engine's vaping calculators to see how the variables change the result in real time. Doing that is an enlightening and worthwhile activity.
Battery drain | Steam Engine | free vaping calculators
Mod range | Steam Engine | free vaping calculators
Coil wrapping | Steam Engine | free vaping calculators
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