Voltage, Amps, and Battery life. Oh my!

[velinn]

So, as a standard eGo user I've been using 1.8ohm cartos forever, and they're fine. I've got an eGo Twist now so I can actually see how things perform at various voltages. I was surprised to see that I can't go higher than 3.5v on the Twist with a 1.8ohm, but when I thought about it, thats exactly the range it's supposed to operate at for standard eGo voltages. I'm getting a perfectly fine vape and it's a consistant vape rather than tapering off as battery life wanes. This is good. But then I started thinking, why have VV at all if 1.8's work great at just 3.5v?

I started playing with an amp/voltage/watt calculator and I noticed that by putting in what I've been vaping my 1.8's and 2.4's at on my Twist that I seem to like 7 watts. I started plugging in 7 watts with various ohm ratings and I noticed something. As the ohms got higher, the amps got lower, even though the watts stayed the same.

So this is the deal with variable voltage right? Same "heat" (watts) but with less battery draw at higher voltages? This was a bit of an epiphany because I'd been assuming that using lower voltage on my Twist meant less battery use, but have I been backwards? 1.8ohm is drawing nearly 2 amps, while 2.8ohms still at my same 7 watts, would only draw 1.5 amps. Will I see much of a difference in battery life between a 1.5 amp draw vs a 2 amp draw, and is it all around safer in general to be using less amps?

 

[rondasherrill]

While the amount of "heat" is a little touchy, because it doesn't take into account the amount of surface area of the coil and other factors, you are *basically* right...

How much battery time you will see really depends on like a hundred different factors such has how long you draw, how often, how much liquid...

It is safe so long as you are inside the amp limit of the battery.

 

[velinn]

Sure, I'm not asking for a specific time frame for battery life because there is no way anyone could know that. But all things being equal, 1.5 amps should theoretically put less strain on a battery than 2 amps, even if the voltage itself is higher, which in turn will net some increase in life.. leading me to the conclusion that I should be using some combination of watts and ohms that uses the lowest amount of amps. Is that correct?

Of course this is all academic. This 1000mah Twist is ridiculous. It's lasting me well over 12 hours at my vape pace, primarily using a 1.8ohm carto. But if lowering the amps can improve the longevity of the device, though, that's a good thing.

 

[rondasherrill]

Sure, I'm not asking for a specific time frame for battery life because there is no way anyone could know that. But all things being equal, 1.5 amps should theoretically put less strain on a battery than 2 amps, even if the voltage itself is higher, which in turn will net some increase in life.. leading me to the conclusion that I should be using some combination of watts and ohms that uses the lowest amount of amps. Is that correct?

Of course this is all academic. This 1000mah Twist is ridiculous. It's lasting me well over 12 hours at my vape pace, primarily using a 1.8ohm carto. But if lowering the amps can improve the longevity of the device, though, that's a good thing.

Think about it this way...

1.5A = 1500mA
2A = 2000mA

1000mAh battery / 1500mA draw = 0.67 hours
1000mAh battery / 2000mA draw = 0.5 hours

Those figures show that under a continuous run circumstance, you would get a little more than an extra quarter of an hour running 1.5A instead of 2A. Obviously we don't vape continuously, but rather a few seconds at a time throughout the day, but you get the idea.

Now, how that would affect the overall life of the device, I can't say. Most quality devices are designed with a "fudge factor", so even at the limit they are still technically fine.

 

[vsummer1]

Think about it this way...

1.5A = 1500mA
2A = 2000mA

1000mAh battery / 1500mA draw = 0.67 hours
1000mAh battery / 2000mA draw = 0.5 hours

Those figures show that under a continuous run circumstance, you would get a little more than an extra quarter of an hour running 1.5A instead of 2A. Obviously we don't vape continuously, but rather a few seconds at a time throughout the day, but you get the idea.

Now, how that would affect the overall life of the device, I can't say. Most quality devices are designed with a "fudge factor", so even at the limit they are still technically fine.

I continue to learn from your posts

The eGo will charge somewhere around 250 times before it dies, so that 1/4 of an hour can really add up over time.

 

[velinn]

Excellent, thank you both very much. That's exactly the info I was looking for.

 

[rondasherrill]

I continue to learn from your posts

The eGo will charge somewhere around 250 times before it dies, so that 1/4 of an hour can really add up over time.

I'm a huge nerd... And I didn't even think about that. Longer run time = less charge cycles = longer life.

 

[vsummer1]

I'm a huge nerd... And I didn't even think about that. Longer run time = less charge cycles = longer life.

I did good then?

 

[velinn]

I did good then?

Sure did, for me anyway. rondasherrill provided the technical, while you provided the application. I had a feeling this was the case but was just a hunch. Thanks to you both for explaining it with numbers. I like numbers. Numbers satisfy my brain better than hunches.

 

[jhfw]

I believe the OP was correct in his original assumption that his battery charge would last somewhat longer when vaping at a lower voltage at 7 watts, but I think it would be hard to notice the difference. At a constant 7 watts the only difference to the battery would be the efficiency of the conversion from a nominal 3.7 volts to either 3.2 volts or 4.8 volts on the Twist. As a bucking conversion is usually more efficient, a setting of 3.2 volts at 7 watts should result in a longer charge time. It does not matter what the voltage or current at the cartomizer is, because the battery does not "see" it, but rather the battery is looking at the regulator circuit.

 

[Off Topic]

If you want a lot of heat, without burning the flavor of the juice, Put a dual coil carto (1.5-2 ohms) on a VV device that can handle 3+ amps.

 

[Bronze]

And there is always component protection considerations. I've always understood batteries are best protected at around 1.5 amps (as a general rule) and should operate at no more than 2.0 amps. Anything above 2.0 amps and battery deterioration increases rapidly and also safety issues come into play as well. Again, it depends on many things the least of which is your battery design. But I think if you keep your amperage below 2.0 amps, you will ensure good battery health.