The real life of a battery

[Nataani]

I frequent and hang out in vape stores quite often. The ones I go to are full of friendly people, who are always out to educate and help fellow vapers out. There is one fact thrown about that I always doubted though, regarding the life of such and such simple ego or vision battery. The owners of these stores frequently state to new customers that the batteries will last for four hours of pressing the button per 1000 mAh. Some math on a paper towel at the store last night confirmed my doubts, much to the shock of the owner.

Here are the specs that the four hour per 1000 mAh claim was last made of:
1300 mAh vision spinner battery - VV from 3.3v-4.8v
2.2 ohm coil on a protank mini (the owner recommended these to the customer).

Battery charge:
1000 mAh translates to 3600 C of charge.
3600 * 1.3 = 4680 C

Amp draw at min (3.3) voltage:
I = V/R
I = 3.3 / 2.2
I = 1.5 A

Amp draw at max (4.8) voltage:
I = V/R
I = 4.8 / 2.2
I = 2.18 A

Battery life at min voltage:
Seconds of use = Charge / current
Seconds of use = (4680 C) / (1.5 C/s)
Seconds of use = 3120 s = 52 minutes

Battery life at max voltage:
Seconds of use = Charge / current
Seconds of use = (4680 C) / (2.18 C/s)
Seconds of use = 2145 s = 35 minutes 45 seconds

From this it is pretty clear that the 4 hours is a little bit of an overstatement.
These statements were made in ignorance, so no hard feelings against the owner for the misinformation to customers. He is the kind of guy that will always give the accurate info if he has it.

So, just for giggles, what resistance coil would actually get four hours of use per 1000 mAh?

Current to get four hours (14400s) of use:
Seconds of use = Charge / current
14400 = 3600 / I
I = 0.25

Resistance to achieve this current at lowest voltage setting:
R = V / I
R = 3.3 / 0.25
R = 13.2 ohms

Preeeeeettttty sure that no device would function at this resistance.

 

[devauto]

Dev wonders if he could get a discount based on actual time versus stated time ... thinks it should be about 1/4 the cost!

 

[InTheShade]

LOL, love it. Never thought to calculate it in those terms.

Well the most frequent number I see thrown out on the forums (and yes, I have used it myself) is an hour of vaping time per mAh. I have always assumed that means real time - so if you have a 1000mAh twist, it should last 10 hours with normal vaping patterns. This can have no possible base in calculated numbers as there are so many variables - I think it was someones best guess and for some reason it has stuck around.

So the question is, is the owner now going to use these revised numbers now or stick to the 4hrs?

 

[Baditude]

MAH, or miliamp hours is a specification that battery manufacturers/vendors use to help determine the capacity, or run time that a battery can be expected to be used before requiring recharging. Many manufacturers overstate the mAh capacity to encourage sales of their product over a competitors. It is not an exact science and not even an accurate figure to depend upon, only to be used as a general guideline.

The standard has been that 100 mAh is roughly equivalent to 1 hour. This can vary depending on a multitude of reasons in how hard the battery is used in practice.

650 mAh = 6.5 hours
1300 mAh = 13 hours

We all know that the above is only a general guideline, and any individual may get more or less time from a battery's claimed mAh rating. One person might get only 6 hours from a 1300 mAh battery, another person may be able to use it for two days.

 

[meanckz]

I frequent and hang out in vape stores quite often. The ones I go to are full of friendly people, who are always out to educate and help fellow vapers out. There is one fact thrown about that I always doubted though, regarding the life of such and such simple ego or vision battery. The owners of these stores frequently state to new customers that the batteries will last for four hours of pressing the button per 1000 mAh. Some math on a paper towel at the store last night confirmed my doubts, much to the shock of the owner.

Here are the specs that the four hour per 1000 mAh claim was last made of:
1300 mAh vision spinner battery - VV from 3.3v-4.8v
2.2 ohm coil on a protank mini (the owner recommended these to the customer).

Battery charge:
1000 mAh translates to 3600 C of charge.
3600 * 1.3 = 4680 C

Amp draw at min (3.3) voltage:
I = V/R
I = 3.3 / 2.2
I = 1.5 A

Amp draw at max (4.8) voltage:
I = V/R
I = 4.8 / 2.2
I = 2.18 A

Battery life at min voltage:
Seconds of use = Charge / current
Seconds of use = (4680 C) / (1.5 C/s)
Seconds of use = 3120 s = 52 minutes

Battery life at max voltage:
Seconds of use = Charge / current
Seconds of use = (4680 C) / (2.18 C/s)
Seconds of use = 2145 s = 35 minutes 45 seconds

From this it is pretty clear that the 4 hours is a little bit of an overstatement.
These statements were made in ignorance, so no hard feelings against the owner for the misinformation to customers. He is the kind of guy that will always give the accurate info if he has it.

So, just for giggles, what resistance coil would actually get four hours of use per 1000 mAh?

Current to get four hours (14400s) of use:
Seconds of use = Charge / current
14400 = 3600 / I
I = 0.25

Resistance to achieve this current at lowest voltage setting:
R = V / I
R = 3.3 / 0.25
R = 13.2 ohms

Preeeeeettttty sure that no device would function at this resistance.

your math makes sense, however you are missing a variable: usage.

you aren't depressing the firing button for 35 to 52 minutes continuously.

most devices have a cut off at 10-15 seconds.
I think this variable was added, when it was suggested that it lasts 4 hours.

just my thoughts...no head for math at the moment

 

[Technohydra]

This is more complex than it seems initially. Whereas you are correct in most of the math, lets simplify.

1300mah is clunky, so let's call it what it is in another form, 1.3 amp hours. So is you are pulling 1.3 amps, the battery can sustain this discharge for 1 hour continuously (in theory, the battery would probably overheat and melt down if we really tried this). This is approximately equal to running a 2.7 ohm coil at 3.7 volts, which is higher resistance than most people ever run.

Using 2 ohms as a comfortable number, we get 1.85 amps, and this could be considered more common usage. That puts you at 1.85 amps, or 42.16 minutes on a perfect charge, perfect battery.

Using 1.8 ohms gives you 2.055 amps, or 37.94 hours, ideal. But, here's the rub: the resistance of the coil will change with heat. The hotter the metal gets, the more it expands, which will lower its resistance somewhat. Large conductor means less resistance, after all.

So in reality, your 1.5 ohm coil may dip down to a 1.3 for the last second of firing, possibly lower or higher, depending. So even with the calculation of time based on specs, there are other variables to be considered that will further reduce the vape time. Starting and stopping the discharge will waste a bit of power, as it takes energy to start the flow of electrons. Also, any heat generated by the battery (on the battery itself, not the atty) is considered an inefficiency in the power source, and is the result of electrical energy converting into heat instead of flowing along the conduction path. The energy from that heat is being generated from the internal resistance of the battery. Also, the hotter an alkaline battery gets, the less efficiency it maintains (google thermal runaway for batteries).

Then there is the fact that energy is being lost in the connections between the battery and the tube, the tube and the 510 connection, the 510 connection and the coil, and those losses happen twice each, once on the negative side and then again on the positive side. The adjustment points for Twists and such also constitute a power loss, as no device is 100% electrically efficient...the list goes on, and each of those values can be different each time the device fires.

*edit* This is one reason why some vapers will praise the virtues of mechanical mods, there are fewer inefficiencies to rob you of your battery power.

 

[chuckie]

That's why a more real time measurement would be ml's of juice used before the battery is dead.

 

[Nataani]

Using 1.8 ohms gives you 2.055 amps, or 37.94 hours, ideal. But, here's the rub: the resistance of the coil will change with heat. The hotter the metal gets, the more it expands, which will lower its resistance somewhat. Large conductor means less resistance, after all.

Actually this is the reverse. The higher the temperature of a conductor, the higher the resistance. This is because resistance is a collisional process, whereby electrons 'collide' with atoms (not really, but it works for the explanation). Since atoms move faster at higher temperatures, collisions are more abundant between electrons and atoms. Yes, the wire expands, but the relatively minor resistance increase due to this expansion is near irrelevant compared to the resistance increase due to temperature.

So in reality, your 1.5 ohm coil may dip down to a 1.3 for the last second of firing, possibly lower or higher, depending. So even with the calculation of time based on specs, there are other variables to be considered that will further reduce the vape time.

So actually, your 1.5 ohm coil will increase in resistance as it heats up, increasing the amp draw and thus even further lowering the battery life.

Starting and stopping the discharge will waste a bit of power, as it takes energy to start the flow of electrons. Also, any heat generated by the battery (on the battery itself, not the atty) is considered an inefficiency in the power source, and is the result of electrical energy converting into heat instead of flowing along the conduction path. The energy from that heat is being generated from the internal resistance of the battery. Also, the hotter an alkaline battery gets, the less efficiency it maintains (google thermal runaway for batteries).

Correct, so in effect, any numbers generated based on my original math are a perfect world scenario. Reality is that the life will be far less than this.

Then there is the fact that energy is being lost in the connections between the battery and the tube, the tube and the 510 connection, the 510 connection and the coil, and those losses happen twice each, once on the negative side and then again on the positive side. The adjustment points for Twists and such also constitute a power loss, as no device is 100% electrically efficient...the list goes on, and each of those values can be different each time the device fires.

Also correct, with also further reduces the life of the battery.

 

[Nataani]

your math makes sense, however you are missing a variable: usage.

you aren't depressing the firing button for 35 to 52 minutes continuously.

most devices have a cut off at 10-15 seconds.
I think this variable was added, when it was suggested that it lasts 4 hours.

just my thoughts...no head for math at the moment

If it was said like that, I wouldn't really care... much. The problem is that usage is so circumstantial. Some people may take four puffs a day, others take hundreds, you cant use numbers like this based on such circumstance.

So the question is, is the owner now going to use these revised numbers now or stick to the 4hrs?

The owner did indeed state that he would stick to the math rather than the original quotes of four hours. How long that battery lasts in every day use, factoring in time between vapes, is based on the persons usage.

 

[Baditude]

That's why a more real time measurement would be ml's of juice used before the battery is dead.

I would have issues with this, too. Much depends upon the juice delivery device used. A factory made coil may use 3 ml in a days time, but put that 3 ml in a rebuildable atomizer and it could be vaped in a matter of a few hours.

 

[Nataani]

MAH, or miliamp hours is a specification that battery manufacturers/vendors use to help determine the capacity, orrun time that a battery can be expected to be used before requiring recharging. Many manufacturers overstate the mAh capacity to encourage sales of their product over a competitors. It is not an exact science, only to be used as a general guideline.

The standard has been that 100 mAh is roughly equivalent to 1 hour. This can vary depending on a multitude of reasons in how hard the battery is used in practice.

650 mAh = 6.5 hours
1300 mAh = 13 hours

We all know that the above is only a general guideline, and any individual may get more or less time from a battery's claimed mAh rating. One person might get only 6 hours from a 1300 mAh battery, another person may be able to use it for two days.

mAh is a statement of charge. 1000 mAh = 3600 coulombs of charge. 1 amp is 1 coulomb per second. So at 1 amp a battery could run continuously for 1 hour.

It seems that battery manufacturers have overstated their batteries capacity by more than ten fold then? As said in other responses, a statement of capacity which depends on usage is a terrible way to go about doing it. Anybody can roughly estimate how long a battery will last them based on a continuous output time.

 

[Baditude]

As said in other responses, a statement of capacity which depends on usage is a terrible way to go about doing it. Anybody can roughly estimate how long a battery will last them based on a continuous output time.

Except one doesn't vape continuously on their e-cig until the battery is dead...at least I sure don't. Even I take a break from vaping to get things done.

When a novice goes into a vape shop and asks how long that battery will last them, you can understand the difficulty in answering that question accurately. Only a ball park estimate can be given, and even then if the customer doesn't get that result they will be disappointed and perhaps even angry that the info given was untrue. There are too many variables involved.

 

[Ryedan]

So actually, your 1.5 ohm coil will increase in resistance as it heats up, increasing the amp draw and thus even further lowering the battery life..

I believe that would be decreasing the amp draw. But not by much

 

[klynnn]

Thank heavens I have more important things to worry about.

 

[beckdg]

internal resistance?
voltage drop?
relation to low voltage cutoff and current in usage?
human duty cycle?

massive variables...

 

[Nikkita6]

your math makes sense, however you are missing a variable: usage.

you aren't depressing the firing button for 35 to 52 minutes continuously.

most devices have a cut off at 10-15 seconds.
I think this variable was added, when it was suggested that it lasts 4 hours.

just my thoughts...no head for math at the moment

This is exactly what I was going to say ... The calculated time of 52 minutes only apply to a continuous discharge of the battery, which is not news to anyone who studies, and understands battery performance. We, as vapers do not continually discharge our batteries during use, we discharge the battery in 3-10 sec bursts.

Based on "actual vape time", the general rule of approx 1 hr per 100 mah is more accurate IMO based on experience. I have a 2000 mah battery that only last about 60 minutes with a continuous discharge at 2A down to 2.75v however, I get about 15 hours of actual vape time from the battery, and I don't discharge my batteries below 3.5 volts.

 

[beckdg]

agreed. i get about 10 to 11 hours out of my 1100mah.

hence the question "human duty cycle?".

 

[Dakota Jim]

but with my chain vaping habits I only get about 10 hours from a "3400"mah battery in my vamo, and about 2 hours from my 650 twist which is why I always have back up batteries and devices on my person at all times