Single vs. Multi Battery Mods
- Thread starter Intuthu Kagesi
- Start date
Look at the circuit(s) above ...
There were a couple of key assumptions; Firstly that the voltage applied to the coil(s) was equal to or lower than a single battery, and secondly, that the regulation mechanism power is excluded
The power consumption is measured AFTER the regulation mechanism
The Voltage being greater than what is "seen" by the coil has no relevance, as it is a potential difference ... YES, it has the potential, but its potential aint being used
Battery life is always cited in Amp hours NOT Watt hours, (The Watts are irrelevant here as the full Potential isn't being used!)
The above has always been my understanding when working with 12 V systems and I have yet to have a car blow up. I use both PWM controllers and MPPT.
The only time I would put a power supply in series is when hooking up low voltage solar panels to get to 14.4 volts for deep cycle batteries.
The only time I would put a power supply in series is when hooking up low voltage solar panels to get to 14.4 volts for deep cycle batteries.
We may well be wrong on this one Stranger IF they are calculating power to include the heat up cool down effect of PWM, however that honestly would be bulls####, or ... that they are for example taking a PWM of say 50:50, and multiplying the power by 50% to compensate for switching losses, but again, that's bull####
The only possible way you could extend the "life" using series batteries in my opinion, would be to allow the joint battery voltage to sag to the required output voltage, however that would be detrimental to the life of the batteries, albeit that it would win the argument
Get a dual battery device and a single battery device and put the same build in both and vape at the same wattage, that's the practical part and if you say you got the same puffs from both you will be the first vaper i have ever met that have found that to be the case we are not just making it up that we get double the vape time we say it because it's the case! I can get all those diagrams and theories within seconds just copying and pasting from the internet but it doesn't effect what happens when i vape!
See below thanks @X-Calibre786
In a regulated mod using 2 batteries in series, the input voltage is doubled. This means that to get the same 30w output, the regulator will only draw half the current. See screenshots below. The only variable changed is the voltage.
Single Battery at 3.7v
Dual Battery in series at 7.4v
Because the current draw is roughly halved, the battery life is roughly doubled.
Credit to Steam Engine's calculators
http://www.steam-engine.org/batt
And the practice matches the theory!
If you are correct Timwis, then you're about to rewrite a number of Physics formula, and I'm only too keen to find out more
I think we have gone way off the rails here. If the variables are the same and within safety limits, IE a .5 coil on a regulated mod, then YES you will get more time(amp hours or puffs) from a dual battery than what you will get from a single battery.
What the debate has evolved into is parallel versus series configuration and the science there can't change
Parallel will increase the amp hours, voltage will remain the same.
Series will increase the voltage, amp hours will remain the same.
What the debate has evolved into is parallel versus series configuration and the science there can't change
Parallel will increase the amp hours, voltage will remain the same.
Series will increase the voltage, amp hours will remain the same.
My information the same as yours is just taken off the internet the difference is what @X-Calibre786 posted from Steam Engine is what i always experience. I have already invited you to try the practice, if you don't that tells me you are not confident in your own theories!If you are correct Timwis, then you're about to rewrite a number of Physics formula, and I'm only too keen to find out more
No all the way through my argument is i get pretty much double the puffs from a dual battery device than a single battery device which @Intuthu Kagesi strongly disputes!
I've managed to lay my hands on a PARALLEL dual battery mod, (an Eleaf iStick) ... I don't have a single battery mod, however this one does run on one and two batteries, so I'll give it a go against itself with one vs. two batteries, and against a couple of newer technology Vaporesso dual battery Gen / Gen S mods with the same tank / build ... Lets see what transpires ...
Don't hold your breath, as this is going to take a few days
I will speed it up with a poll, seems you are making it up as you go along lol.
I would like to point out that this applies to regulated mods only. The input and the output of the regulator circuitry will have differing voltages, currents, resistance, and power. Read more about that at the link provided above.
We are talking regulated mod theory only I take it.
In your example you assume that the PWM output is 'always on'. For PWM this is not true as the duty cycle is a series of switched on full and switched off full cycles where the 'ON' cycle determines how much power is effectively delivered. A 50% duty cycle should equate to roughly 50% of what the battery can provide. It would also mean that max current is not drawn from the battery all of the time, as the coil does not see 'all the power' all the time. It is switched on and off for short periods of time and an 'average' amount of power is spread out based on the duty cycle.
PWM circuits typically supply a lower voltage than the input voltage, so for mods, typically below 4.2v. Using multiple batteries in series means that the total effective voltage at the output can be stepped up as well - 4.2v, 8.4v. 12.6v etc.
Using your example with Ohm's Law to calculate a few things in reverse, we have :
Power = 15w
Resistance = 0.5 ohm
So current through the coil should be 5.477A - check.
Voltage across the coil should be 2.738V - check.
Battery = 3.65V
Resistance = 0.5 ohm
So current should be at 7.3A ? - not check.
Power should be 26.645W ? - not check.
Is the PWM circuit just dissipating 11.645W into heat energy and drawing an extra 1.8A just for switching stuff off and on?
This is likely not the case, or if it was, nobody would use PWM in any application as it does not seem to be very efficient.
The snag here is that it is not just a simple series circuit. Using your example, and a perfect world scenario, let's check it again but at 65 Watts, which we all know a single 18650 mod should be capable of.
To produce 65 Watts across a 0.5 ohm coil, the Ohm's Law calculations would have the voltage across the coil at 5.7v and the current at around 11.4A. But yet we only have a fully charged single battery of 4.2v.
Now we know the battery is definitely at 4.2v and that we are producing 65W of power across the coil. Using Ohm's Law again, this now calculates that the current should be at around 15.476A. Huh?
This suddenly does not equate, as either Ohm's Law has been totally stuffed since inception, or we have some serious Devil's magic happening here.
You cannot measure it as simple as you have, as the input (battery side) and the output (coil side) are not directly connected. There are other discrete components that switch on and off for simple PWM so the current across the coil is an average of the full on / full off duty cycles.
For Buck and Boost circuits there are also discrete components that switch on and off but also store and provide either reduced or increased power to the output in the place of the battery. The switching rate and power gained or lost is just governed by some clever monitoring done on top of the buck or boost to retain the output within the parameters you set via the interface, be it Volts, Watts, or a specific temperature.
For regulated mods, if you assume that the circuitry is 100% efficient, do the calcs for the COIL side separate to that of the BATTERY.
Using what we know of the OUTPUT or coil side:
Power = 15W
Resistance = 0.5 ohm
Current is then 5.477A through the coil
Voltage should be 2.739V across the coil.
Using what we know on the INPUT or battery side:
Power = 15W
Voltage = 3.65V
Current drawn from battery = 4.11A
Obviously this is in a perfect world, so depending on efficiency of anything between 90-95%, you can add the additional 5-10% to the current drawn and actual Power dissipated on the INPUT side of the equation to determine safe limits.
If you can calculate the current drawn from the batteries based on their capacity and the input voltage you can easily prove that dual batteries in a series or parallel configuration will effectively last twice as long as a single battery counterpart. Taking your battery at 3.65v (or 2 at 3.65V) , 0.5ohm coil and 15W as an example:
The actual time may not be 100% accurate as time remaining at 3.3V is still theoretically 33 minutes, which means that from 4.2 volts, you should get around 9-10 minutes of continous vaping till the batteries reach the 3.3V cut-off.
The reduced current draw from using 2 series batteries with a higher input voltage or using 2 parallel batteries providing double the mAH capacity, does support the increased vaping time if you look at the figures.
9-10 Minutes of ~ 2 second puffs = 270 puffs, which seems about right. 540 for a dual battery.
9-10 minutes of ~ 3 second puffs should be around 180. 360 for a dual battery.
So, who's counting puffs that can back this up?
For a 2500 mAH battery, you can theoretically provide 10.5 Watt of power one full hour before the battery goes to 0v. But then we don't use them down that low do we.
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Time to sit back and watch
You are about to rewrite the physics formula yourself when you do this exercise.
Welcome to practical versus theory
Sent from my LYA-L09 using Tapatalk
I won't hold my breath for an apology for the couple of patronising comments such as:
https://www.ecigssa.co.za/single-vs-dual-battery-device-poll.t68839/
One person voted in error which he has explained so if you voted you are the only one out of 12 people at the time of writing this message who doesn't get double the battery life with a dual battery device, would be interesting if you did vote as it shouldn't be included as you have just admitted you don't even have a single battery device to compare!
If you are correct Timwis, then you're about to rewrite a number of Physics formula, and I'm only too keen to find out more
https://www.ecigssa.co.za/single-vs-dual-battery-device-poll.t68839/
One person voted in error which he has explained so if you voted you are the only one out of 12 people at the time of writing this message who doesn't get double the battery life with a dual battery device, would be interesting if you did vote as it shouldn't be included as you have just admitted you don't even have a single battery device to compare!
Currently on 400 Puffs. This is waaaaaaaaaay more than I would usually vape on an 18mg liquid. And about as much as I can stomach. Barely made a dent in the battery levels. Going to fire up the single battery Drag X tomorrow and see where the battery lies after 400 puffs. 
Probably won't even quite get to 400 lol!
Get a dual battery device and a single battery device and put the same build in both and vape at the same wattage, that's the practical part and if you say you got the same puffs from both you will be the first vaper i have ever met that have found that to be the case we are not just making it up that we get double the vape time we say it because it's the case! I can get all those diagrams and theories within seconds just copying and pasting from the internet but it doesn't effect what happens when i vape!
See below thanks @X-Calibre786
In a regulated mod using 2 batteries in series, the input voltage is doubled. This means that to get the same 30w output, the regulator will only draw half the current. See screenshots below. The only variable changed is the voltage.
Single Battery at 3.7v
Dual Battery in series at 7.4v
Because the current draw is roughly halved, the battery life is roughly doubled.
Credit to Steam Engine's calculators
http://www.steam-engine.org/batt
And the practice matches the theory!
In practice I get through about 5-6ml of juice on a single batt 18650 Mod and about 10-12ml of juice on a double batt 18650 mod. Pretty much the same coil, wattage and vaping style. So roughly double the juice throughput.
Thank you Kuhlkatz, now that's a plausible answer built on fact that makes sense as apposed posting anecdotal unsupported comments.
In a nutshell, you're saying that the PCM does in fact run at "full power", (obviously less the controlling overhead), and that the output is an effective voltage based on the duty cycle?
I'm intrigued by your comments on buck and boost too ... clearly buck is easy enough, however boost at the currents used for vaping? ... Do you know how this is achieved? or is this just for the processor?
This covers the theory and operation of the simple buck converter : https://en.wikipedia.org/wiki/Buck_converter
And this one the boost converter : https://en.wikipedia.org/wiki/Boost_converter
This YT video was already posted elsewhere on the forum, but it offers an easy to understand description of the two via the visuals:
This is obviously heavily simplified compared to all the circuitry that is actually in most mods, but describes how they can effectively step up or step down the voltages based on what we select for the power across the coil.
With dual series batteries effectively providing a usable input voltage range of 8.4V down to 6.6V, there is less need to boost the voltage than on a single battery of 4.2V down to 3.3V.
Lets see if this gets linked or not (yep, it did) - Watch the two below if you have a few minutes for a full lecture.
There is no debate necessary.
Early in this thread I provided Battery Mooch's gospel on this. Nobody doubts his knowledge on batteries and vaping. All the issues debated here are clearly explained by Mooch in the video I provided. Hence no debate necessary.
Watch from 10 mins but I strongly recommend that you watch from the beginning.
Early in this thread I provided Battery Mooch's gospel on this. Nobody doubts his knowledge on batteries and vaping. All the issues debated here are clearly explained by Mooch in the video I provided. Hence no debate necessary.
Watch from 10 mins but I strongly recommend that you watch from the beginning.
A regulated mod exchanges volts for amps and vice versa as needed and cell configuration actually has little impact on that part of the equation. Working with a higher input voltage does however reduce the effect of circuitry resistance thereby losing less potential as a result of conductor voltage drop. The input end of the circuit can also be designed to deal with lower current levels which makes it more cost effective and reliable and allows for the use of smaller components.
In short its easier to keep the magic smoke inside the parts when running in series. And in as much as it makes no difference total available amp hours before the circuit wizardry equals total available amp hours at the coil end.
Regards
In short its easier to keep the magic smoke inside the parts when running in series. And in as much as it makes no difference total available amp hours before the circuit wizardry equals total available amp hours at the coil end.
Regards
Very good write up here.
https://www.zamplebox.com/community/unregulated-parallel-vs-unregulated-series-box-mods
https://www.zamplebox.com/community/unregulated-parallel-vs-unregulated-series-box-mods
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