How does a regulated mod increase battery voltage to maintain desired wattage?

[mcclintock]

I know we jest with the unicorn comments but we have to understand we are dealing with specific limitations in order to keep a vape device marketable in terms of cost, size, functionality and efficiency. That is not to say there are poor designs out there, but many employ a design limitation for a reason. You can take an input voltage range of 6.4 to 8.4 volts (dual series mod), and generate ~24.5 volts through a boost converter that is needed to run a 3 ohm coil at 200 watts, but what components are required to perform such a task and will the final product still be marketable in terms of size and cost?

I would like to draw a correlation with audio power amplifiers. In order to achieve a linear output, an audio amplifier should double its power output with each half of speaker impedance. So a 50 watt amplifier into 8 ohms should output 100 watts into 4 ohms and 200 watts into 2 ohms. Many consumer, even professional amplifiers are unable to achieve this, some struggle with a 4 ohm load and many just give up the ghost with a 2 ohm load. Why is this when speaker impedances fluctuate across their audio band? It is not because this design objective is unobtainable, but because the designer made a choice to sacrifice a linear output for say cost, efficiency or even form factor (size). One can purchase amplifiers that double their power output for every half of speaker impedance (even with both channels driven), and are stable down to a 2 ohm load - but many of these amplifiers cost the same as an average car and require a team of professional wrestlers to carry the behemoth into your listening room. It’s all relative of design, and if you want something small and inexpensive, you are limited with what speaker you can use with it.

Keith Bontrager, a key figure in the bicycle industry, came up with this quote in terms of bicycle design – Strong, Light, Cheap…you can only pick 2 when designing a bicycle. This analogy, although by changing the wording to a degree, can be applied to many industries.

I'm not sure it's even practical to build a 3 ohm coil that will take 200W. At any rate, any wanting that kind of power that experienced mechs will try to use .05 ohm or something. Also nickel wire for TC is super low resistance. The possible range is far wider than the audio amplifier analogy. Regarding which, why have an amp that produces maximum power at a load that few will use? It will have to be a large amp to have enough power at 8 ohms too, although you exaggerate, I just took a Adcom GFA-555 off the high shelf by myself yesterday.

 

[Punk In Drublic]

I'm not sure it's even practical to build a 3 ohm coil that will take 200W. At any rate, any wanting that kind of power that experienced mechs will try to use .05 ohm or something. Also nickel wire for TC is super low resistance. The possible range is far wider than the audio amplifier analogy. Regarding which, why have an amp that produces maximum power at a load that few will use? It will have to be a large amp to have enough power at 8 ohms too, although you exaggerate, I just took a Adcom GFA-555 off the high shelf by myself yesterday.

My comment is not about the practicality of a 3 ohm coil at 200 watts. I used a common resistive ceiling of 3 ohms to demonstrate the needed maximum voltage for a typical 200 watt device. A 3 ohm coil can easily be achieved. A 3 ohm coil that requires 200 watts, or better put 24 volts is extreme and rare. But my response demonstrates how 200 watts in unobtainable with the typical resistive ceiling of many devices given their voltage limitations.

My correlation with audio amplifiers is to demonstrate the choice of design. The goal with doubling power with every half impedance is to create a near perfect linear scale inline with the fluctuating impedance of a typical loudspeaker. The Adcom GFA-5555 is not reaching that perfect linear scale (200 watts into 8 ohms, 325 into 4 ohms). It does not have to operate at full 200 watts – even 5 watts into 8 ohms should double to 10 watts into 4 ohms, and 20 watts into 2 ohms if required.

Live performance does not follow these limitations, thier dynamics are infinite. We have the capabilities of reaching closer to that infinite dynamics. But designers choose specific limitations in order to achieve specific goals. In the case of the Adcom, the goal is to build within a specific price point. Not discrediting Adcom, excellent amplifiers for their price (also own an Adcom amp). But realistically, it can not hold a candle to some amps that do not follow the same design limitations.

 

[stratus.vaping]

So, what is the alternative to adjust power output on the fly?

Tricky problem without semiconductors, when our rare metals run out you could try this

 

[Baditude]

I can't tell if you're joking or serious. What am I looking at and how does it work? Why is it better?

 

[DaveP]

This anology reminds me of those massive Klipschhorn audio loudspeakers that I used to drool over at the high end audio store. The salesman would lightly tap the ends of the speaker wires with a 9 volt battery and you'd hear and feel such a loud THUMP! from the speakers that the sonic wave would move your hair.

Circuit City sales people had all the reasons you should buy that $1000 sound system. All we needed was a Subwoofer to round out the sound realism of our current setup!

 

[DaveP]

I can't tell if you're joking or serious. What am I looking at and how does it work? Why is it better?

It's the mechanical version of a Triac or SCR creating a variable voltage output with a wire wound slider!

 

[Baditude]

It's the mechanical version of a Triac or SCR creating a variable voltage output with a wire wound slider!

I think I'll take a pass on something so archaic and use something I know works like my many variable power regulated mods .

 

[DaveP]

So, what is the alternative to adjust power output on the fly?

A buck-boost circuit can do that by varying the power by increasing/decreasing the voltage, but current varies with P=EI (power =voltage x current), so amperage delivery capability varies as the circuit demand rises and falls. It's why multi-cell mods have become popular.