Battery and resistance calculations

[breno]

One thing you should perhaps be aware of is that the power output is proportional to the voltage squared (assuming the atomiser resistance is fixed).
So whilst a voltage drop from 5 to 4 is (5-4)/5= a 20% drop, the power drop is (5^2 - 4^2)/5^2 = (25-16)/25 = 9/25 = a 36% drop.

So a small change in voltage produce a much larger change in power.

for example going up from 5v to 7v virtually doubles the power, and presumably nicotine inhaled!!

[mnealtx]

It doubles the power - but I don't think it doubles the absorption. It DOES seem to give a better 'kick', though.

[Dave Rickey]

You can regulate (stabilize) current by adjusting voltage, or you can stabilize voltage and let current shake out as the balance between voltage and resistance. You could theoretically adjust resistance as well as one of the other two, but in practice trying to stabilize more than one is pulling on two ends of the same string without considerably more logic than you want or need in an eCig.

In the end, what you're after is wattage applied to vaporizing eLiquid, you can't really control your resistance because the atomizer has the amount and gauge of NiChrome it has, and that's it (you can add to resistance, but not dynamically in any meaningful sense).

If you stabilize either voltage or current, you get away from the variable vapor production that plagues eCigs as the cell winds down, with the downside that as the cell voltage drops your logic is going to draw more current from it, and if the overcurrent/undervoltage protection fails (or you're using unprotected cells) you've supplied the feedback conditions for a thermal runaway (making other forms of over-current or under-voltage protection important).

Because what we're after is wattage, and load resistance is not variable in any meaningful sense, current regulation is our best route to stabilizing vapor output. Combine that with user-controlled airflow (through restriction or how hard they suck) and you can get a much more consistent result, at least within the limitations of atomizer reliability.

--Dave

[Robert]

If your using a resistor- then your battery is heating a resistor.

I use an inline voltage regulator.

[breno]

Originally Posted by Robert

If your using a resistor- then your battery is heating a resistor.

I use an inline voltage regulator.

I think a voltage regulator will still produce heat.
I was think they would be a good idea too because I realised a resistor
would heat up, now I am thinking how do those regulators work?

I think the basicially do the same thing as a resistor in a round about way.


Anyway here is a picture of one:-




Note it has aheat sink on it or where it can be attached to a bigger one.

Here is a much more sophistated one, notice the whopping great heat sinks!!





I think the first one is a simple transistor, and the name comes from shortening "transfer resistance" and that is what they basically do, they transfer resistance in to the circuit.

So I am not to sure if is any better.

[mnealtx]

Originally Posted by Robert

If your using a resistor- then your battery is heating a resistor.

I use an inline voltage regulator.

And you (and I, since I use one too) are heating them up just like a resistor would.

[mnealtx]

Originally Posted by breno

I think the first one is a simple transistor, and the name comes from shortening "transfer resistance" and that is what they basically do, they transfer resistance in to the circuit.

So I am not to sure if is any better.

The name 'transistor' came from a combination of transmitter and resistor. It's more like a rheostat - you can go from a virtual open to a virtual short (minus bias losses).

[Dave Rickey]

A linear regulator is electrically just a self-adjusting resistor, you're still shedding the excess power as heat and your efficiency is no better than the ratio between the input voltage and output. A switching buck regulator can be much more efficient (90-95% being pretty typical), it works by turning the current off part of the time, then smoothing the output in an inductor. But you need at least two more components; a capacitor and an inductor, the inductor being the physically large part of that, the more you're stepping the voltage down, the bigger it has to be to turn the sawtooth output into a steady voltage, feeding a sawtooth into an atomizer would probably be bad (repeatedly cause the physical join between the NiChrome and the leads to flex, that being the usual source of total failure).

--Dave

[quovadis]

This is a naive question.

If what you guys say is true, then we should get the Chinese to build an atomizer with a perfect ohm resistance amount to satisfy different vapers using different voltages?

[Þornbjörg]

Related... I found a nice bit of testing done on various high capacity 18650's, with actual capacity at various rates... might be worth including for knowledge.

CandlePowerForums - View Single Post - New 18650 with 3000mAh from KD

If you're customizing atty resistance, you probably would consider a custom battery, so now you can intelligently decide on best battery performance too!