This is a new composition of my own blog entry at http://www.e-cigarette-forum.com, this one....
People is getting excited about the new temperature-controlled, variable wattage mods. But regardless its new possibilities, they remain a genuine VW mod. Time to remember what really they are...
Mech user gets this constantly wrong. Well, some of them, at least. So accustomed to regulating their power output varying their atomizer resistances, they stay spot on that idea even when the electronic module inside their VW devices lets them much more freedom, and safeties, to get what they want.
Temperature control just takes advantages from the capability of changing power applied to the atomizer, not only as a setting point set up by the user, but as a constantly changed power point in response to the average temperature of the resistance. It is checked out precisely by the resistance measure and its variation with temperature, and that is why kanthal and nichrome alloys cannot work well in those mods: those alloys have an almost flat change of their resistivity with temperature, forcing big errors on that monitoring. It is needed a well known resistivity curve, usually for pure or almost pure metals, or alloys well controlled and that exhibit measurable changes with temperature, that is, a non-flat curve.
But the fact that those metallic compounds and alloys, like nickel-200 (Ni-200), titanium, and so on, have resistivities much lower than kanthal and nichrome adds more confusion to the task. A typical kanthal resistor for sub-ohming (getting high power) on a mech is about 0,3 - 0,6
Ω, but with Ni-200 is not uncommon to get into the 0,1 - 0,4 Ω. the electronics are ready for that, as we will see soon, but that doesn't mean that this brings up more power...
Temperature control runs coils with a lot less resistance, so the current applied would be higher, according to Ohm's law, even if the wattages are the same as in normal. But they will be in a constant state of flux, if the temperatures detected are near the setting point, as the electronics
throttles up and down power to manage temperature.
Seems fair to ask if in temperature control mod is set more or less strain on the batteries than in
conventional VV/VW mods. Let's see all that in detail....
The thing about VV/VW and their electronics control module is that they
effectively separate atomizers and batteries. It's like it appeared a
voltage transformer between both parts (and in many senses it is). They
call it DC-DC converter, and their maths are relatively simple. All the
energy (or energy per time unit, i. e. power) drawn from the battery is
converted in the same energy (power) applied to the atomizer, it just
interchanges voltages and currents. but remembering that P = V * I it's a
simple math.....
Well, there are some energy losses inside the converter, a yield (or efficiency) factor involved, which usually falls in the 0,90 through 0,96 (or 90% up to 96%), which means that the energy drawn from the battery is partially lost (the difference between 100 and the yield in %) as heat in the innards of the converter. It's an unavoidable toll to get constant power through the decay of the batteries.
Having said all that, your applied current through the atomizer, even in the case of very low resistance (nickel and temperature control active), doesn't matter much. It's about power applied, and then requested to the battery, plus the losses. The batteries always works at its natural voltage output (4,2 fully charged, and so on), so it doesn't matter (at first approach) how the electronics feed the atomizers, it does count how much power the electronics pull from the battery, and from that power, the current is fixed by the P = V * I formula, as V is a fixed parameter.
On second approach, yields do change over the current and power applied over the atomizer, but its changing is not so big if you work between boundaries of the electronics, and usually the electronics are controlled by some logics to cut output outside the boundaries, hence the low resistance, check atomizer, high load, etc., messages.
Some people have said that as the electronics cut off partially power once the temperature of the coil pass over the setting point, in this mode the power consumption (i.e. draw from the batteries) is even lower. But that supposes you're running your atomizer dangerously near the dry-hit without temperature control. My opinion is that temperature control is a big step forward, but it cannot improve our taste buds, and surely it wasn’t their intention: they are far better detectors of the 'dry-hit' situation......
Let's take an example: in a DNA40, vaping at 39 W over a 0,5 Ω coil, that same power plus the losses are drawn from the batteries. The resistance does not count, we have the power!
Well, there are some energy losses inside the converter, a yield (or efficiency) factor involved, which usually falls in the 0,90 through 0,96 (or 90% up to 96%), which means that the energy drawn from the battery is partially lost (the difference between 100 and the yield in %) as heat in the innards of the converter. It's an unavoidable toll to get constant power through the decay of the batteries.
Having said all that, your applied current through the atomizer, even in the case of very low resistance (nickel and temperature control active), doesn't matter much. It's about power applied, and then requested to the battery, plus the losses. The batteries always works at its natural voltage output (4,2 fully charged, and so on), so it doesn't matter (at first approach) how the electronics feed the atomizers, it does count how much power the electronics pull from the battery, and from that power, the current is fixed by the P = V * I formula, as V is a fixed parameter.
On second approach, yields do change over the current and power applied over the atomizer, but its changing is not so big if you work between boundaries of the electronics, and usually the electronics are controlled by some logics to cut output outside the boundaries, hence the low resistance, check atomizer, high load, etc., messages.
Some people have said that as the electronics cut off partially power once the temperature of the coil pass over the setting point, in this mode the power consumption (i.e. draw from the batteries) is even lower. But that supposes you're running your atomizer dangerously near the dry-hit without temperature control. My opinion is that temperature control is a big step forward, but it cannot improve our taste buds, and surely it wasn’t their intention: they are far better detectors of the 'dry-hit' situation......
Let's take an example: in a DNA40, vaping at 39 W over a 0,5 Ω coil, that same power plus the losses are drawn from the batteries. The resistance does not count, we have the power!
The 'at X Ω'
does not add more relevant info . Let's say for the sake of this
example they are about 50 %, that is, at 3,7 V of output voltage. That is supposing you are in a 'one battery' scenario, like most DNA40.
In the
side of the atomizer (with 0,5 Ω coil)
you are effectively putting about 8,8 A, but in the side of the
batteries, with a typical 93% of yield, you are pulling out 42 W, and at
3,7 V that means 11 A. The atomizer resistance (being that with nickel
or with any other material) does not count for these calculations, it
only appears in the atomizer side once you need to know the current
applied, but with very different resistances (like kanthal and nickel
ones), provided they are inside the electronic boundaries, the power and
battery drain are essentially the same.
Nearly all VV/VW have some built-in safety measures to avoid shortcircuits, less than desirable settings and thermal overruns over the circuitries and batteries. The first and foremost one is about the effective separation between atomizer and battery, with the electronics in the middle taking care of the situation. They can also detect a drained battery, which needs a recharge ('low batt' message), and an old of abused battery which needs full replacement ('weak batt' message). How nice is that? And how it is done?
About the 'weak battery' message. DC-DC converters monitor the
voltage output of batteries so they can warn us about their state (cut
off near depletion, i.e. 'low batt' message). They do that in two ways: monitoring voltage output
without load (it should be over 3,2 - 3,4 V) and monitoring the voltage
drop when batteries are under load. If the voltage drop is bigger than
some specified parameter the converter interprets this as a weak battery, if the voltage without load appears normal.
Of course, that happens because internal resistance of lithium batteries grows up as the using time go up. that opens up the possibility of mistakenly label a fresh battery as old and weak. How?
Of course, that happens because internal resistance of lithium batteries grows up as the using time go up. that opens up the possibility of mistakenly label a fresh battery as old and weak. How?
Try to feed a VV/VW device with a battery tinier than it deserves, like a 18350 instead a 18650 (with the proper adaptor) or a 5 A Li-Co unprotected 18650 battery, and ask it for 30W of output. the electronics will detect the drop in output voltage of the battery and mistakenly will label it at a bad battery. It is not, but surely it is the improper batttery to feed our mod, because at 30 W a minimum of 10 - 12 A of output will be drained from the battery!
But in case of being using a proper high drain battery, if that message appears and it is confirmed, you have an aged or mistreated battery which needs to be replaced. Less likely, you can also have a battery compartment dirty, with its contact plates oxidized, and that also adds voltage drop to the battery, forcing the 'weak batt' battery, but instead
is a weak connection. So a close inspection of this might be worthwhile too.
Just to end this hefty volume (someone should cut my fingers!....
), the equations involved, a derivative of the well known ones from Ohm's law:
where η
is the greek letter 'eta', usually used for this yield/efficiency
matters in engineering and physics.... According to Evolv's statements,
DNA40 is rated at 93%.
