High amp vs high voltage?

[Mikes1992]

I've always wondered whats better for efficiency. In a regulated mod I can't imagine it really makes a difference in vape performance, I'm currently keeping my builds at a lower resistance by winding parallel coils. My goto build comes to about 0.4ohms and I run it in the range of 28-38w, usually set at 32w, if I wound it in series it would be around 1.6ohm which would need about 7v to get to 30w and at my Aegis solos max voltage of 8v would provide 40w. The only issue with this is that it limits the wattage range you can run at, since I sometimes do crank this build upto 42w, although it does start to burn above 45w.

The one advantage of running at a high voltage and a lower current is that theoretically there should be less energy loss in the transmission of power to the coils (like in the pin, the posts and the wiring connecting the 510), although depending on the construction of the mod/tank it may not be significant enough to provide any benifit. I can imagine that it's not that simple either as the mod is having to boost the voltage more which may cause the voltage conversion efficiency to suffer. Although in my dual cell mod it may be benificial since the input voltage is around 6.4-8.4v, although I tend to use this for my higher wattage builds.

This may just be me because I'm obsessed about how much voltage is dropped across cables, I always use the high quality wiring and keep it as short as possible because it is actually quite surprising how much energy you can loose through a cheap cable. Even good quality wire at higher amps can drop a significant amount of power.

 

[mimöschen]

Just a side note:
Main problem is that most multiple cell devices lack a boost circuit, so that the output voltage limitations of the device may become a problem for high voltage vaping.
In most common dual 18650 devices the actual output voltage is a limiting factor for instance, because it varies between 7.5 and 5V depending on the cells charge state. That in turn limits your actual resistance range in that it forces you to build lower, especially if you want a consistent vape at or above 60W.

But even if a mod has a boost circuit, its buck circuitry is more efficient in general, which again would be a pro for low resistance builds.

The best bet may however be a build that doesn't need (much) buck or boost for your desired wattage in the first place.
Just like a mech, the output voltage per cell will never exceed 3.8V and will drop with further use to about 3V.
Bearing that in mind, calculating your target resistance with 3.4/3.5V may be a good idea. For a single cell device at 40W that means the sweet spot is at about 0.3ohms.
On multi cell devices you should calculate with the minimum output voltage for your desired wattage due to lack of boost capabilities though, which would equate to about 0.6ohms at 40W.

 

[AttyPops]

Dual cells will either be parallel or serial.

These days (wisely) they're [For] parallel you draw only 1/2 the amps from each cell, but for vv or +v you have to use a booster, and that has some efficiency loss too. Serial has its own problems, as "stacked" batteries stress the "top" battery a lot during high drain. We used to stack them in the old days, but we used high ohm coils and vaped "at 5 ish vots" with a cheap voltage regulator (buck). And IIRC we used protected cells.

There were some that stacked them in mechs, but that's normally a bad idea unless you're tracking and pairing the batteries well (and again, fuses or protection recommended).

So there's a lot of mechanics to all this stuff beyond "high amp vs high volts". In general I'd guess that the less you stress your parallel batteries because you've halved the amp draw, the better off you'll be, since resistance and heat are interrelated. And protection circuits are great things, IMO.

All batteries have some degree of internal resistance. And the less heat you build up in them, the longer they'll last. And probably safer too. After all it's heat the causes the runaway effect when they go thermal due to breakdown of the electrolyte. I think. Pretty sure. Mooch could tell us more.

And then there's circuitry designs....

Oy.

 

[Punk In Drublic]

The majority of dual cell regulated devices these days are in series battery configuration. This is to increase the input voltage in order to meet the higher power demands a typical dual cell device offers. Because we are dealing with a higher input voltage, current draw is theoretically the same as a parallel config for a given wattage request. Excluding circuit efficiency...

50 watts with dual series at 6.4 volts = 7.8 amps at the battery
50 watts with dual parallel at 3.2 volts = 7.8 amps at the battery

Circuit efficiency can fall in favour to any configuration. Unfortunately we do not have examples of this with vape devices, but there are many examples to be found that display the efficiency of a boost/buck circuit. Efficiency could resemble a bell curve where it peaks somewhere in the middle of its operation. Or it could be a gradual increase/decrease. All dependent on circuit design and the components used.

Internal wiring will favour high voltage over high current. The loss will obviously be dependent on the type of wire used, it’s size (gauge) and length.

 

[AttyPops]

OK, I stand corrected, although maybe just be coincidence the dual builds I've see are parallel. Regardless, the point remains, there's many variable to "efficiency". And don't stress your batteries. You're certainly better off with two parallel batteries than one battery.

 

[AttyPops]

oh, BTW, it's been a long time, but stacking has a problem of stressing one of the two batteries more, so you still have to make sure that you use "good batteries" that can take the load.

I don't remember the details, but yeah, stacked was a problem. Maybe only in mechs and with overload, but I think in general. "They" used to rotate stacked batteries so as to evenly wear them, and pair them up. IDK if people still do that or not.

 

[Punk In Drublic]

Current between 2 series batteries will be identical – one battery will not be working harder than the other. However...because batteries may not be perfectly matched (we do try our best), then there is the possibility one is operating at a slightly lower voltage.

2 batteries in parallel are going to be dependent on the integrity of the connecting circuit and or wiring. Again, this may not be perfect therefore one battery could also be working harder than the other.

Both configs have their faults

 

[Coolsiggy]

Interesting the restive nature of our coils and regulated devices and associated circuitry. My mesh setups at times exhibit a lack of consistency over time and I have wondered if this may be due to a gradual contact degradation. The mesh coils mostly use clamps and flat surface contact by design, could be that the contact surfaces degraded.
I often change from TC mode to Power mode to compensate, almost as if a restive change has occurred under load but not on the mod when reading coil ohms.

 

[DaveP]

FWIW, this chart covers vaping voltage and resistance and shades the chart into optimum (and not so optimum) vaping conditions. It's been around for many years. I suppose it was created for mech users in the earlier years of vaping.

https://i.pinimg.com/originals/93/5d/40/935d408827b496c739710b99411363bb.jpg

 

[Punk In Drublic]

Sorry but that chart is meaningless. There is no correlation between resistance and mass. Resistance can be obtained by many different means, but it is the coils mass and Specific Heat Capacity of the metal that dictates it’s needed power.

Example: 1 ohm goal using Kanthal (to remove Specific heat as an influence). 1 ohm coil made out of 28 gauge wire would be vastly different than a 1 ohm coil made out of 24 gauge wire. If we were to use a 4 volt source, 1 ohm would yield an output of 16 watts. 16 watts into the 28 awg coil would be very usable. 16 watts into the 24 awg coil would not.

 

[DaveP]

Sorry but that chart is meaningless. There is no correlation between resistance and mass. Resistance can be obtained by many different means, but it is the coils mass and Specific Heat Capacity of the metal that dictates it’s needed power.

Example: 1 ohm goal using Kanthal (to remove Specific heat as an influence). 1 ohm coil made out of 28 gauge wire would be vastly different than a 1 ohm coil made out of 24 gauge wire. If we were to use a 4 volt source, 1 ohm would yield an output of 16 watts. 16 watts into the 28 awg coil would be very usable. 16 watts into the 24 awg coil would not.

Sure, mass slows heat rise, but voltage applied to a given resistance is at least similar among coils of differing wire gauges and types, assuming that the power supply can deliver amperage needed to the coil. Few of us take coil winding as seriously as you do. If it's not delivering the vapor, we crank up the wattage or drop the wire gauge to something that fits our vaping style.

I agree that for a mech mod coil, wire type, gauge, and voltage calculations matter much more than for an electronic mod.

 

[Punk In Drublic]

Sure, mass slows heat rise, but voltage applied to a given resistance is at least similar among coils of differing wire gauges and types, assuming that the power supply can deliver amperage needed to the coil. Few of us take coil winding as seriously as you do. If it's not delivering the vapor, we crank up the wattage or drop the wire gauge to something that fits our vaping style.

I agree that for a mech mod coil, wire type, gauge, and voltage calculations matter much more than for an electronic mod.

Not sure I understand your response. Non the less, it does not change the fact that chart is wrong. Where’s the physics that states any one of these resistances results in a hot or cool vape as depicted in that chart? How is the temperature defined? Is it one second on the fire button or 10 seconds? Is 30awg used to make a 1 ohm coil or 24 awg?

The factors behind heating a coil include the metals specific heat, it’s mass, the amount of power applied in watts and time. Resistance will become a factor only if dealing with a voltage source but the outcome is still watts so it is just an added calculation to the above. We can also include airflow but given this is not a static factor given the many different variables, it becomes difficult to calculate.

 

[dripster]

There were some that stacked them in mechs, but that's normally a bad idea unless you're tracking and pairing the batteries well (and again, fuses or protection recommended).

Stacking them in mechs is a great idea because with the cells hooked up in series the current is always equal for each cell. (Even, if the voltage is not.) Cells hooked up in parallel in a mech is where the weakest cell receives the biggest amp load, and that in fact is why you need to factor in an additional safety margin when calculating battery safety for parallel (and paraseries) mechs. With a stacked mech, or series mech if cells are charged to a somewhat different voltage for whatever your excuse might be, like, for example, one is fully charged to 4.2V, one is charged to only 4.1V, then typically what will happen is you will still feel the vape getting way too weak for you to still want to continue vaping it, a very long time before the latter cell can get overdischarged below 2.5V, at which point this cell would become a safety hazard.

If, however, you put in a fully charged cell plus another cell that you forgot to charge after you took it out of some regulated mod so that the latter cell is at 3.2V, not 4.1V, that's when you might get yourself in trouble if you haven't familiarized yourself with how the vape in question should normally feel like (how it should feel like if both cells are fully charged, that is). Even so, you'd still probably notice the vape getting real weak really fast just before that, but anyway it would still be a risk so, to avoid making such mistakes, it's always a good idea to use a married set... it avoids the possible confusion, and also it avoids the added risk inherent of putting in cells with vastly dissimilar remaining cycle life (i.e., the added risk of not noticing it when the oldest cell is nearing end of cycle life, albeit you can check if you have a charger that measures cell capacity and you know how to use that to keep track of cell capacity, how degraded capacity translates to depleted cycle life).

My point is that, as long as you don't make it a habit of yours, vaping a stacked mech with one cell being at a somewhat (!) lower voltage like I described in my first paragraph, although not recommended of course, isn't such a cataclysmic safety error. Doing so every once in a blue moon isn't going to break the married set, and, you're not going to vape it down below 2.5V, as you'll feel it on the vape a long time before it even reaches down to 3.5V, let alone reaches down to 2.5V.

Finally, putting a fuse in a mech is a wee bit silly these days, as it defeats the whole purpose of going for a mech when you can always just go for a decent regulated mod instead. As for the reason why I don't recommend vaping a stacked mech with the cells at different voltages, it's because there's always going to be someone getting it all wrong, i.e., it just tends to add more confusion to a situation that can be already too confusing to some, in which case it would be equivalent to an added risk of human error. Then again, so is driving a car........

 

[AttyPops]

I only made the comment for discussion, because somewhere in the deep recesses of memory, stacking batteries was "scary" to some in a mech. People would swear they'd "NEVER!!!!" stack batteries. Etc. But maybe that was years ago, and before we had better battery knowledge. IDK, wasn't my thing. But protection was a big issue back then too, and now everyone sub-ohms and lol...idk that you can even get fuses or protection for those watts. YMMV.

The point was there's a lot of variables and "other considerations".

 

[dripster]

Sure, mass slows heat rise, but voltage applied to a given resistance is at least similar among coils of differing wire gauges and types, assuming that the power supply can deliver amperage needed to the coil.

On a mech, yes that would be a fair conclusion, more or less. More or less, as the voltage sag of the battery still gets affected by current, and, current is determined by Ohm's Law so as a result the differing wire gauges and types still matter to some non-negligible extent when calculating the voltage going into the coil, i.e the coil resistance resulting from these two factors does─and the DC internal resistances of multiple cells hooked up in series are summed the same way that their voltages are also summed, so basically in a dual battery stacked mech the combined voltage sag resulting from this fact is (quasi) doubled when compared to using a single battery mech at half the wattage number you use for the dual battery series mech. I.e., if the reason you're going for a stacked mech is to be able to vape at twice the power, then logically, at the coil you'll be getting a total of twice the voltage sag also in addition to that, so you won't be getting the full 8.4V at the coil.

So in a dual battery stacked mech you could lose up to as much as a whole volt, or more, and still not have taken into account the voltage drop, or power loss resulting from the resistance of the actual mod itself, albeit you can try to measure it accurately and add that to your (also accurately I should hope) measured coil resistance to calculate the current, and to then calculate the volts also in addition to the current. The easiest way to calculate is if you start first by summing al the resistance numbers.

Few of us take coil winding as seriously as you do. If it's not delivering the vapor, we crank up the wattage or drop the wire gauge to something that fits our vaping style.

That's mainly the result of many advanced coil builders having been bullied permanently away from ecf, as those who don't take it as seriously are often very serious about their not taking it very seriously. At 120 watts and upwards, the difference in vape experience between simple round wire (or parallel round wire) builds and intricate, complex builds is magnified much to the point of reading through naysayers' comments as if claiming there are no colors in a rainbow... not pointing my fingers at you or anyone else in the thread, but the systematic derogatory belittlement coming from some certain individuals aimed against experienced complex coil builders does get really boring, really fast........

I agree that for a mech mod coil, wire type, gauge, and voltage calculations matter much more than for an electronic mod.

Yes and no. For the type of electronic mod that's an unregulated electronic mod, such as my Surric X-Vault, which is a true PWM mod (famous classic), all the calculations matter a whole lot more than many think, despite it uses a potentiometer dial and a standard car fuse to simplify a few things.

 

[dripster]

Not sure I understand your response. Non the less, it does not change the fact that chart is wrong. Where’s the physics that states any one of these resistances results in a hot or cool vape as depicted in that chart? How is the temperature defined? Is it one second on the fire button or 10 seconds? Is 30awg used to make a 1 ohm coil or 24 awg?

The factors behind heating a coil include the metals specific heat, it’s mass, the amount of power applied in watts and time. Resistance will become a factor only if dealing with a voltage source but the outcome is still watts so it is just an added calculation to the above. We can also include airflow but given this is not a static factor given the many different variables, it becomes difficult to calculate.

You're still forgetting the biggest factor of them all. Focused and powerful airflow that, due to coil positioning and airflow adjustment working in tandem and working as a function of the strength of your draw, remains consistently stable enough (the so-called Coandă effect, which causes the amount of turbulence to be rather limited─both at the coil's actual surface itself and in the nearby space that is located behind the downwind side of the coil...), in cohort with fast evaporation with juice flowing fast out of the cotton into the numerous, interlinked, tiny cavities and crevasses in a complex coil build that uses multiple strands of relatively thin wire sizes to profoundly increase the juice adsorption rate of the actual coil itself, is what provides the most powerful cooling effect that you can try to imagine. A freezer uses the evaporation of a liquid substance to extract heat away, and, what most people don't realize is that increased airflow in tandem with increased airflow stability across the liquid surface is what speeds up the evaporation even more. So it isn't just about increasing the liquid surface area, and it isn't just about supplying more cold air to achieve more thermal conduction that will extract the heat away, as liquids evaporate faster in contact with just air than they do in contact with dense vapor, when the evaporation itself is providing the biggest portion of cooling effect.

 

[Punk In Drublic]

You're still forgetting the biggest factor of them all. Focused and powerful airflow that, due to coil positioning and airflow adjustment working in tandem and working as a function of the strength of your draw, remains consistently stable enough (the so-called Coandă effect, which causes the amount of turbulence to be rather limited─both at the coil's actual surface itself and in the nearby space that is located behind the downwind side of the coil...), in cohort with fast evaporation with juice flowing fast out of the cotton into the numerous, interlinked, tiny cavities and crevasses in a complex coil build that uses multiple strands of relatively thin wire sizes to profoundly increase the juice adsorption rate of the actual coil itself, is what provides the most powerful cooling effect that you can try to imagine. A freezer uses the evaporation of a liquid substance to extract heat away, and, what most people don't realize is that increased airflow in tandem with increased airflow stability across the liquid surface is what speeds up the evaporation even more. So it isn't just about increasing the liquid surface area, and it isn't just about supplying more cold air to achieve more thermal conduction that will extract the heat away, as liquids evaporate faster in contact with just air than they do in contact with dense vapor, when the evaporation itself is providing the biggest portion of cooling effect.

I did not forget airflow, as stated “We can also include airflow but given this is not a static factor given the many different variables, it becomes difficult to calculate.”.

 

[dripster]

I only made the comment for discussion, because somewhere in the deep recesses of memory, stacking batteries was "scary" to some in a mech. People would swear they'd "NEVER!!!!" stack batteries. Etc. But maybe that was years ago, and before we had better battery knowledge. IDK, wasn't my thing. But protection was a big issue back then too, and now everyone sub-ohms and lol...idk that you can even get fuses or protection for those watts. YMMV.

The point was there's a lot of variables and "other considerations".

There's a reason why mechs are called advanced vaping devices and why there exists the disclaimer of "for advanced users only". The only way to deal with it, aside from staying away from mechs altogether, is to get educated─and to get educated properly of course.

 

[dripster]

I did not forget airflow, as stated “We can also include airflow but given this is not a static factor given the many different variables, it becomes difficult to calculate.”.

I wasn't referring to airflow. Rather, I was referring to the coils and the related subject of complex coil builds, how the juice flows out of the cotton into the coils, and the relationship between the temperature of the coils and it.