Regulated mod battery question

[crazywesc]

I was just wondering how to get the most battery life out of a regulated mod.

What build would yield a longer battery run time.

.5ohm-3.8v-7.7amp=30watts
1.2ohm-6v-5amp =30 watts

Is it the amp draw or voltage that would limit the battery run time?


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[Miata GT]

Amps measure the flow of current so it would be safe to say that all else being the same a higher amp discharge of the battery would result in shorter battery life for the charge.

 

[jackrussel]

30 watts in both cases, so I'd think they should the same. The 0.5 ohm coil might give a slightly longer runtime because the voltage required is closer to the actual voltage of the battery. Less regulation "should" equal less loss.

 

[novamatt]

Basically, the answer here is that your build doesn't matter, the wattage does.

So this is oversimplification, but basically what these boxes do to get the higher voltage is pull extra amps from the battery and convert it. The wattage stays the same throughout the circuit. Since we know the battery's feeding 4.2v on a full charge and we know the wattage, we can figure out the amp draw from there. Your coil resistance doesn't touch anything on the battery side, so it doesn't make a difference to battery life in a variable mod.

Let's talk through the numbers on your two buids.

.5ohm-3.8v-7.7amp=30watts or 1.2ohm-6v-5amp =30 watts
Your atomizer is seeing 3.8 volts and 7.6 amps at 28.88 watts in this first build. On the other side of the chip, to get that 28.88 watts with a 4.2v input, the battery's putting out 6.88 amps. In the real world, you lose a little bit to the chip, so it's really closer to 7.94 amps at 33.33 watts, figuring your mod has 90% efficiency. On a fresh 2500mah battery, that gives you about 17 minutes of vape time or 208 five second pulls.

For your second build, the numbers work out to 30 watts at the atomizer, so (again assuming 90% efficiency), you're getting 7.94 amps at 33.33 watts going into the chip. Battery life is essentially the same, with 17 minutes or 200 five second pulls.

If you swich it to a 15 watt setting, you're only pulling 3.97 amps from the battery, with a 33 minute/400 pull vape time, so half the watts = double the battery. Doubling the watts to 60 gives you 8 minutes/100 draws, so double the watts = half the battery. Make sense?

Steam engine has a battery life calculator you can use to run the numbers. Play with it a little and see what you find.

 

[crazywesc]

Great explanation! And thanks for the link. The steam engine calculator is pretty nice!


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[MrPlink]

Watts in, watts out

 

[Signmaker]

Watts in, watts out

Watts...up?
Doc

 

[Norrin]

Steam engine although usually good seems to fail here. It is assuming that batteries drain linearly and that we can use the full capacity in these devices and both of those assumptions are wrong. Because of this the higher the resistance the longer the battery will last at the same wattage, although the difference might be that small as to be negligible if you are not approaching the batteries limit it will make a difference and a larger one the closer to the amp max you approach.