Technical information of atomizers

[Vapinginjapan]

Does anyone have any hard information on how much power atomizers are able to draw during heating at standard 3.7v?

I assume this is related to their resistance.. but haven't yet been able to find the technical specs on them yet.

Like, how many amps are able to flow through them, assuming an unlimited source of power.

I'm thinking wiring super capacitors in between the battery and the atty would give all of the amperage the atty could ever want, while evening out the load on the battery so as to prolong battery life.

Haha, with such a setup, dual attys inside a single e-cig could be quite doable, while promoting long life of the attys by reducing the maximum load each one is required to bear. I imagine two attys at 3 volts would do better than 1 atty at 5 volts, in terms of combined life span.

 

[Tugger]

Old posts show a resistance of 3-4 ohm for atomizers. You can figure it out from there.

 

[Vapinginjapan]

Thank you much. Sorry if i'm asking an old question.

 

[ApOsTle51]

Atomizers can draw up to 1000mA , all vary on atomizer type of course.

 

[Vapinginjapan]

Disclaimer: Assertions of the cause of battery death warrants further research after Vape's post below. Take with a grain of salt.

Actually, my findings from using various calculators over the internet differ slightly

At 3 ohms, we're looking at 1.6A at 5V, and 1.2A at 3.7v
At 4 ohms, we're looking at 1.2 @ 5 and 0.9 at 3.7

Now, this may be the cause of all of the dying batteries, because max amperage draw depends on the battery capacity.

A quick look at battery space says that their 1400mAH battery can supply 2.6A, and through extrapolation we can assume that the 250mAH batteries can supply less than 0.5A at their rated voltage safley.

THIS is probably the cause of batteries dying quickly, to be honest. The super high draw on the battery is killing the battery in 30 recharge cycles instead of 300, where it's supposed to be at.

My sollution to this, is to wire in a super capacitor (A tiny super capacitor capable of storing just enough energy for a puff would be able to provide 5A, a super capacitor able to supply energy for a whole cigarette can deliver 15A. ) or use LiPO packs (Have since found out that these are probably too dangerous to use in normal e-cigs) , which can deliver shocking current for their size (A 750mAH LiPO can deliver constant power at about 7 amps. )

This would allow the atomizers to draw their full current, in a small battery package , for high power low weight setups.

Or lithium iron phosphates that can survive 4A+ @ 2200mAH and be recharged nearly 2000 times.

I have the feeling a 1000mAH lithium iron phosphate would outlive atleast 20 mini E-cig batteries at 250mAH (given that some people kill them after 2 weeks, which i'm thinking is 30 recharges, outlasting 30-40 wouldn't be unthinkable) for relativley comparable price. That, and at 1000+ mAH, you'll be recharging much less often, which will mean even MORE battery longivity. If you assume an average 250mAH battery will last 100 recharges, which is about a month and a half at 2 recharges a day, a 2200mAH LiFEPO4 will last about as long as 100-200 'lesser' e-cig batteries, which will save GOBS on shipping and battery costs.

Now, my amp draw numbers could be completely fudged, but I still think that unless i'm off by atleast 100%, the batteries are poorly matched to the atomizer needs.

 

[Vape]

I believe you might be thinking of mah incorrectly. The mah is the storage capacity of the battery, the current draw depends on the load and the supplied voltage.
A 1400 mah battery will provide 84 amp minutes:
1400 mah = 1.4ah times 60 minutes = 84 amp minutes
A 250 mah battery:
250 mah = .25ah times 60 minutes = 15 amp minutes

3ohms = 1.2a @ 3.7V
4ohms = .9a @ 3.7V

A 1400mah battery will power a 3ohm load @3.7V:
84 amp minutes divided by 1.2a = 70 minutes or 93.3 minutes @ 4ohms
A 250 mah battery will power same load:
15 amp minutes divided by 1.2a = 12.5 minutes or 16.7 minutes @ 4ohms

Both batteries will supply the needed current, the mah just decides for how long.

Yes a battery will heat up under a continuous load, increasing internal resistance, decreasing it's ability to deliver a constant current under load.

But the batteries are only on for 3-7 seconds at a time so I don't think the battery is going to heat up much considering the load is not constant.

 

[Vapinginjapan]

The larger a battery is, the more current it can handle before a catastrophic drop off in total power delivered.

Take, for example, the graph entitled 'discharge rates' on this website
Battery Performance Characteristics - How to specify and test a battery

You can see that the battery suffers a significant total power capacity hit when discharging at the higher currents.

I'm not entirely sure whether this phenomenon is due to the discharge intensity, or the heating of the battery.

If it is based on discharge intensity, then indeed, we suffer a hit in battery capacity when discharging at high amperage

If it's based on battery heat, then as you say, there is probably enough cooling time between draws to keep the battery cool (And operating at maximum efficiency.

If anyone could clarify this, it would be most appreciated.

I'm also under the impression that high discharge currents can shorten the life of the battery, whether they're contingent in the absolute amperage draw the battery is suffering at the time, or whether this degradation occurs at a continuous load, I'm not sure. My theory about battery death in Lithium ions being accelerated by the current-spike usage pattern in e-cigs hinges on this distinction.

However, further research into the maximum current draw of lithium ions motivated by your post seem to show that e-cigs are, in fact, within design specifications for their battery size. Hmm. Food for thought.

At any rate, something needs to explain unusual failure rates for batteries that never make it to their 300 recharges.

At any rate, you have given me a lot to think about. Hopefully my post will flesh out my reasoning a bit more. Your assertion of battery capacity scaling with heat has given me more impetus for research into the matter. It is appreciated. Thank you.

P.S. My assertion about LiFEPO4's being a vastly superior battery technology for e-cigs still stand, as far as battery pack life goes.

 

[ISAWHIM]

Amp/Hour is divided by minutes, not multiplied by minutes...

1400mAh = 1.4Amps per hour = 0.023333Amps per minute

85 amps per minute, would be 5100 amps per hour!
(I know what you were trying to say was that a 1.4A device will draw a load of 85A in a second, but it only draws 1/60 of that in 1/60 of the time. Amps are AmpHours. A device which is 0.023333A will run for 60 hours on a 1.4Ah source. Devices don't use the hour mark, only supplies of power, not consumers of power.)

Just use amp/hour... that is the standard. No sense converting to micro-chip or pico-power draining formulas. (Micro-devices use Amin, Asec, mAhr, mAmin, mAsec, uAhr, uAmin, uAsec. We only use mAh here, because that is the standard on the small battery.)

1200mAh will run a 1.2A device for an hour. The batteries acutally last for about 30(0.50hr) to 20(0.33hr) minutes of constant draw time, so the 250mAh battery is giving around 500mA to 750mA to the device.

Yes, a super-capacitor with a fill/drain regulator will/should help save the battery life, and the coil. You need a resistive filling of the capacitor, and resistive draining of the capacitor, or it will fry the computer chip and the coil in one dump. As it stands now, the chip and the battery resistance play a role in the heat delivered to this raw device.

Remember, capacitors drain fast, but they also fill fast, and would drain more potential amps from the battery than the high resistance coil and the amp-limiting microchip. (This is why the manual versions generate more fog/heat/burn, as they have zero regulation, other than the coil itself. It becomes a balance of power without regulation. As opposed to having any real control without the required microchip regulator.)

 

[ISAWHIM]

This is what I use for my calculations...

3 Ohms coil (Assume it is lowest recorded value. Resistance increases as it heats.)

20 average tokes per cig. (20 cigs X 20 tokes = 400 per pack)

One battery lasts for about half a pack, for me. (400 / 2 = 200 tokes)

My average toke is roughly a solid 5.5 seconds. (200 tokes X 5.5 sec = 1100 seconds)

1100 seconds = 18.33 minutes, so I say around 20 minutes of total operating time.

250mAh = 1 hour @ 250mA, or 20 min @ 750mA. (In a perfect world.)

So, I assume the device draws (750mA) or 0.75A, lasting only 20 solid minutes. This makes the coil 3.5Volts @ 0.75Amps = 2.625Watts.

However, that is only with a fresh battery. Voltage operates as low as 1.5 in the computer, so...
3.5Volts @ 0.75Amps = 2.625Watts
to
1.5Volts @ 1.75Amps = 2.625Watts
http://batteryuniversity.com/partone-22.htm

3 Ohms tells you nothing other than the initial cold-coil stress on the battery. The battery resistance is quite possibly 5-6 Ohms average, which is why the coil doesn't just fry when hooked directly up to the battery. As the coil heats, it increases in resistance, an the voltage drops, causing amps to rise and level-off. Somewhere between 0.75A and 1.75A. (Long hot tokes = shorter battery run time and more battery damage. Short cold tokes = longer battery run time and less battery damage.)

You need at-least a 12 Ohm resistor between the battery and the super-cap, so it fills slower than it draws, however, that also reduces voltage. Between the coil and the cap, possibly a matching resistance resistor of 3 Ohms, so it discharges at half the speed that the load would normally have placed on the battery.

Super-caps don't loose stored capacity fast, so losses would be minimal. Unlike a normal capacitor, which would continue to drain the battery even without the device being used.

You would need a good solid-state mosfet switch between the coil and resistor, to open the gate, and another one bypassing the resistor between the coil and cap, to supply unresisted regulated power, and possibly another one to the battery, for when the cap drains out below voltage. (Voltage will drop sharply in a second, at the high-amp draw, and battery-power will have to be fed into the coil directly, but now coil resistance should be up to the 12 Ohms, from the heat.)

Unfortunately, all of that will not fit into an e-cig, and will require a box that is roughly twice the size of the battery itself.

This is why they use direct power, and a CPU to regulate power.

However, with the super-caps, and one resistor, you could also play the balance-act. You would just need an external quick-charge pack, to refill the multiple caps. (I keep calling these devices booster-packs, as they provide non-linked boosts of extended power. I forget who sells them, but they exist.)

 

[ISAWHIM]

P.S. I believe I too... have that a little backwards...

3.5Volts @ 0.75Amps = 2.625Watts
to
1.5Volts @ 1.75Amps = 2.625Watts

Might actually be... (Amps estimated wrong above)

1.5Volts @ 0.75Amps = 1.125Watts
to
3.5Volts @ 0.32Amps = 1.125Watts

(Because the average would be more at the lower running voltage @ 0.75A, since the battery is never constant high voltage. I believe that is what I determined by the specs on the USB pass-through connections.)

Avg power being around 2.5V, Avg amps being around 0.535Ah, Avg wattage being 1.34W.

That works-out to the coil itself being around a 1-Watt device, while the constantly on computer draws the remaining 0.34Watts over time. (The 20 min total puffs + the 4 hours of constant drain from the chip, listening to see if you are sucking on the twig. 0.34W = 0.136A, which would be divided by 4 hours, 0.136A / 4 = 0.034A or 34mAh for the CPU stand-by power drain and operation waste. This is another reason the manual switch on the cheaper models without the computer, may last longer, or as long, but still deliver more puff power. No power is wasted on the high-draw cpu chip.)

 

[Vape]

Amp/Hour is divided by minutes, not multiplied by minutes...

1400mAh = 1.4Amps per hour = 0.023333Amps per minute

85 amps per minute, would be 5100 amps per hour!
(I know what you were trying to say was that a 1.4A device will draw a load of 85A in a second, but it only draws 1/60 of that in 1/60 of the time. Amps are AmpHours. A device which is 0.023333A will run for 60 hours on a 1.4Ah source. Devices don't use the hour mark, only supplies of power, not consumers of power.)

Just use amp/hour... that is the standard. No sense converting to micro-chip or pico-power draining formulas. (Micro-devices use Amin, Asec, mAhr, mAmin, mAsec, uAhr, uAmin, uAsec. We only use mAh here, because that is the standard on the small battery.)

1200mAh will run a 1.2A device for an hour. The batteries acutally last for about 30(0.50hr) to 20(0.33hr) minutes of constant draw time, so the 250mAh battery is giving around 500mA to 750mA to the device.

Yes, a super-capacitor with a fill/drain regulator will/should help save the battery life, and the coil. You need a resistive filling of the capacitor, and resistive draining of the capacitor, or it will fry the computer chip and the coil in one dump. As it stands now, the chip and the battery resistance play a role in the heat delivered to this raw device.

Remember, capacitors drain fast, but they also fill fast, and would drain more potential amps from the battery than the high resistance coil and the amp-limiting microchip. (This is why the manual versions generate more fog/heat/burn, as they have zero regulation, other than the coil itself. It becomes a balance of power without regulation. As opposed to having any real control without the required microchip regulator.)

Thank you for clarifying, I knew it was to late for me to try and do math!
Excellent and very correct info!

 

[ISAWHIM]

Your head was in the correct place... Just a clerical error. (I do it all the time.)

I still want to see a super-cap version soon. But I have my own task at hand. (It uses a super-cap, but not as a primary, only a tiny one, for initial boost.)

I believe that with this whole FDA thing... We will see a few required changes happen, in light of standards and regulation of vapor delivery, which is not present now. (Not present from model to model, or even in the same models.)

The killer being the lack of adjustment from user to user, and lack of anti-abuse control of the device.

With a cigarette, you get ~2mg each cig... from cig to cig, pack to pack, carton to carton.

With these, using a 20mg cart, you could get 0.1mg - 5mg per cig equivalent. (This is where the FDA is focusing on the term "Abuse", in the device. While the "Abuse" in the liquid is bottles unmarked, wrong labels, false doses, and unregulated dose from bottle to bottle.)

I don't care about the liquids, I can manufacture them on my own, if needed. My focus, like yours, is on the device and device power.

Funny how everyone "Claims" to have the "First patented electronic cigarette", yet no-one can provide a patent of the devices being sold. (Patents are for other devices, which are not being sold, and do not actually function.)

Soon, we will dominate this market! LOL... errors included!

 

[patgwashere]

my head hur8-ots

 

[kender]

vapinginjapan a super cap is a good idea, I havent thought about that.
It would put less stress on the battery. Cameras use that for the flash circuit.

 

[mogur]

Very clever calculation of the average current, ISAWHIM. Indeed, if 250mAh is consumed in the equivalent of 20 continous minutes, then the average current is 750mA. It is well known that the inrush current for resistive heating elements is typically 10 times the average current for the first 10-50 msecs. This leads to the conclusion that the inrush current would be almost 7.5 amps! Of course, this would also mean that the demand on the battery would be a 30C (C = specified charging rate for the battery, generally equal in magnitude to the Ah rating) discharge rate. That rate of discharge is unlikely since it would cripple the battery almost immediately, long before it could deliver its promised charge. Speaking of promises, that mAh rating is calculated in the best interests of the people marketing the batteries. It is measured at a .05C discharge rate, not 30C. I understood the 901 battery to be about 190 mAh, delivering much less than that in high discharge situations, more like 80 or 90 mAh.

More perplexing is the fact that if the coil resistance is 3 or 4 ohms when cold, it's likely to be 30 or 40 ohms when hot. That would take at least 22 volts to supply an average current of 750mA. Even at 12 ohms, the battery would have to deliver 9 volts. But regardless of any quibbling about specifics, I love your intuition about how to pin down the average current. My wild conjecture, using your logic, is about 250mA average, with an inrush of between 750mA and 1A, limited by the PWM functionality of the micro-processor. In switched mods, it is limited by the ability of the wires and battery itself to deliver anything much above one amp. Also just a guess on my part.

1.5Volts @ 0.75Amps = 1.125Watts
to
3.5Volts @ 0.32Amps = 1.125Watts

First, li-ions don't do 1.5 volts. They often are protected above 4.2 volts and below 3 volts to avoid damage (and danger to the public). Ecig batteries are not protected because the charger limits the charge to 4.2, and the micro probably protects undervoltage conditions. I would hazard a guess that switched mods are protected by the user simply not trying to continue puffing after the voltage drops too low to vape. Their nominal voltage, meaning average, is 3.7 volts. Second, why would you equate the wattages of these two situations anyway? Everyone knows a room heater has a specified wattage, but that is only with the nominal line voltage applied. I guarantee that a 1500 watt heater will not be a 1500 watt heater if you change the applied voltage.

3 Ohms tells you nothing other than the initial cold-coil stress on the battery. The battery resistance is quite possibly 5-6 Ohms average, which is why the coil doesn't just fry when hooked directly up to the battery. As the coil heats, it increases in resistance, an the voltage drops, causing amps to rise and level-off.

A li-ion has a moderate internal resistance of about 65mOhms when new and less than 150mOhms when well used. Also, when resistance increases and voltage drops, amperage falls off, it most certainly does not increase. It is simple ohms law.

That works-out to the coil itself being around a 1-Watt device, while the constantly on computer draws the remaining 0.34Watts over time. (The 20 min total puffs + the 4 hours of constant drain from the chip, listening to see if you are sucking on the twig. 0.34W = 0.136A, which would be divided by 4 hours, 0.136A / 4 = 0.034A or 34mAh for the CPU stand-by power drain and operation waste. This is another reason the manual switch on the cheaper models without the computer, may last longer, or as long, but still deliver more puff power. No power is wasted on the high-draw cpu chip.)

I don't know where you got 1 watt for the heater, leaving a third of a watt for the micro, but a 34mA drain would deplete a 190 mAh battery in six hours alone. I think maybe the micro has a nanoAmp sleep mode that allows them to last overnight, and to be shipped.

Love the supercap idea, I think there are more than a few of us that have been jonesing to play with that. A boostbuck converter might squeeze into a light weight battery holder if you keep the frequency high enough for small components. You guys have me wanting to break out my test equipment and see what the scope will actually show about the battery currents, thanks for the inspiration, ISAWHIM, Vape, and Vapinginjapan.

 

[Vapinginjapan]

I was thinking of the Maxwell boost cap.

The BCAP PC-10 is 2.7v normal voltage, holds 10 farads, which if I understand correctly is ~0.2mAH, however it can supply a max current of 2.5 amps (8A short circuit)
.

Alternatively, the Maxwell boost cap PC-25 is 25 farads, or 0.6mAH, 2.7v, max continuous 3.75A, surge of 7A (well suited to the surge current of the atomizer, if what you say is true) and 2 of these in a series with a resistor could provide some pretty kickin voltage.

At 25 farads, it'd last about.. a 5 second puff, which is decent. Slowly recharges from the Lithium ion at a constant rate.

I wonder if there's a way to wire the Lithium ion with the super capacitors and a diode to let them work together to power the atty, letting the super capacitor strictly handle the surge load.

At any rate, with 500,000 cycles to 80% capacity, even at 0.6mAH, they'll still outlast 5 normal batteries at 300 charge cycles a battery. And we all know that many batteries die well before this.

Glad to see someone shares my enthusiasm for the potential for supercapacitors to extend the life and enhance the performance of standard Lithium battery systems in e-cigs.

 

[mogur]

Didn't mean to imply that it actually draws 7 amps, rather that it is unlikely to have an average current of .75 amps since that would imply a huge inrush current. In any case, that inrush is very brief, only tens of milliseconds and just a tiny fraction of the ignition time. Take your average 40 watt light bulb on standard 115vac household current. It has a cold resistance of 30 ohms and takes a 3.8 amp inrush current, quickly dropping to .38 amps as the resistance of the heated filament reaches 300 ohms. Or an Estes model rocket igniter at 12 vdc that has an inrush of 15 amps and an ignition current of only 1 amp.

A supercap may be ideal for an ecig, but they have a few quirks to work out. First is the fact that unlike a battery, whose voltage dips but doesn't plummet, the voltage of the cap will decline in a linear fashion, meaning that only the top 20 or 30 percent of its capacity is directly useable. 3.3 volts is the lowest voltage a 901 battery will sufficiently heat up an atomizer, but that is most of its capacity. To get the remaining capacity out of the supercap would require a boost converter to keep the voltage up. On the other hand, since the inrush is so brief, maybe that slice of power is just perfect. It'll take some experimenting or an expert to figure out.

Also, as ISAWHIM has said, there are some balancing and current limiting issues to resolve. Li-ions can blow up in your face if backfed from a supercap and overcharged, for example. A micro and a couple mosfets may be the answer, since the micro has input, output, comparator, ADC, and PWM capability built in for about $2 a pop.

 

[mogur]

Oops, I'm totally wrong about nichrome and inrush current. Tungsten filaments and rocket ignitors do have high inrush, but after intense research, I have found out that nichrome has a very low coefficient of thermal resistivity. Wish I had discovered that fact before making all my above speculations.

It also means that a supercap is much less interesting. Although lightweight and capable of quick charges, the supercap just doesn't have the power density that modern batteries have. Without a current inrush problem, they probably are not a breakthrough tech for an ecig. If you could get one to supply all the current required for one long puff, though, there is the possibility that a pocket carried battery pack or a plugged in tabletop charger could replenish its charge between puffs, since it would take a full charge in a few seconds.

Most of you probably are familiar with RjG's atomizer rebuild- [can't post link cuz i'm a noob] Cigar rebuild - PICS (Bling v2). 38ga nichrome (.004 in dia) and 3.5 ohms per inch. He found the original 4.3 ohm coil too cold and ended up with a 3.3 ohm coil. He tried longer wicks, bigger wicks, smaller wicks, and god knows what else, but concluded that varying very far from the factory specs produced worse results. Without changing to an entirely new technology, the current atomizers probably aren't fertile ground for a breakthrough improvement.

How about one of those wicked pocket lasers that can light a match? Heat up a ceramic or mica slug and do away with broken heater wires? [wickedlasers dot com]