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triple 18650 vs dual 26650
- Thread starter Woody213
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both would be the same. Stacking batteries can be very dangerous. It should be avoided at all costs on a mechanical mod. On a newer regulated mod you can get away with it but you MUST mark your battery pairs. Meaning you always start with a pair of new batteries and mark them so they only get used together. Batteries wear out differently depending on the use so you never want a situation where one battery "has more juice" than the other is it'll end up charging the weaker battery.
This is a vastly understated description of the concerns, but until you have time to carefully research stacking rechargables I suggest you avoid it.
This is a vastly understated description of the concerns, but until you have time to carefully research stacking rechargables I suggest you avoid it.
Voltage is additive in series and common in parallel.
Amperage is common in series and additive in parallel.
Parallel splits the amp load between batteries. Series doubles the voltage (if it's two batteries).
Power (watts) is calculated using two variables. Voltage and resistance (ohms). You can achieve high power by increasing voltage or decreasing resistance. Saying there's only one way to get big power is wrong.
Amperage is common in series and additive in parallel.
Parallel splits the amp load between batteries. Series doubles the voltage (if it's two batteries).
Power (watts) is calculated using two variables. Voltage and resistance (ohms). You can achieve high power by increasing voltage or decreasing resistance. Saying there's only one way to get big power is wrong.
This is all primarily regarding mechs because variable power devices work differently.
Since parallel splits the amp load you can safely build to lower resistances without exceeding the batteries limit. This allows for safely hitting higher watts. Series allows hitting higher watts at higher resistances because the voltage is doubled. If you're using the same resistance in a parallel and series setup, the series would make more power. To make equivilant power with both setups you would be working with much lower resistances in the parallel mod. Minor differences in resistance impact power more the lower you go in ohms. For example:
4.2v and .1 ohm = 176.4watts
4.2v and .15 ohm = 117.6watts
4.2v and 1.1 ohm = 16.0watts
4.2v and 1.15 ohm = 15.3watts
As you can see a .05 ohm difference makes a huge difference at low resistances, but almost no difference at higher resistances. Now look at what it takes to get a 176-117 difference with double the voltage:
8.4v and .4 ohm = 176.4
8.4v and .6 ohm = 117.6
Instead of a .05 difference it's a .2 difference. Making big power with series causes you to use larger resistances and slight differences in resistance don't have as much of an impact on power.
If I were to build a dual battery, unregulated mod I would consider the power range I was trying to have it operate in, play with the numbers and then decide which battery configuration was going to be easiest on the batteries and easiest for me to build with.
The application should be considered before deciding which battery configuration is preferred. I would prefer lower voltage with parallel batteries until I got up to a high power range that caused higher voltage with higher resistances to make more sense. For me that change over would probably happen somewhere pretty close to 100 watts. If I was staying under 100 I would use a parallel setup. Going above that and I would probably want to switch to a series setup.
So I did some quick math comparing parallel to series. I used the max that either set up could use in both volts and amps, just for the math not that it would actually work that way. According to my math a dual parallel at 4.2 v and 60a would require a .07 build and it would yield 252w and a series at 8.4v and 30a would require a .28 build and yield 252w as well. So they are break even? Again Im just using these numbers for the math to show the specs, not actually talking about real world numbers
4.2v and .06ohm is 294watts. You can use either voltage to make the same watts, but lower voltage requires lower ohms and the lower the ohms the less margin of error you have. At the above numbers one hundredth of an ohm is a 40 watt difference. Also, you're pretty close to a dead short. Bottom line is making big power is better done using higher voltage. Manipulating numbers is different than manipulating actual materials. If you're gonna build an unregulated mod and use it for vaping at power ranges over about 100 watts the smart thing to do is use a series setup. A resistance of .1x is sketchy. A resistance of .0x is frankly pretty dumb. Using 8v instead of 4v allows making big power without having to even mess with .2x ohms.
We are discussing the safest and most logical way to do things. If you have some constructive criticism to share or something to add please do. I don't see anything wreckless or unsafe being suggested.
Haadkoe
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Im sure he was joking, but he might actually have a point. How many amps sent through a drip tip does it take to stop someone's heart?
Possibly not many, as it turns out.
http://www.allaboutcircuits.com/vol_1/chpt_3/4.html
Possibly not many, as it turns out.
http://www.allaboutcircuits.com/vol_1/chpt_3/4.html
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Haadkoe
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Maybe, but:
What is the best battery for medical devices?
One of the most energy-hungry portable medical devices is the heart defibrillator. The battery draws in excess of 10 amperes during preparation stages. Several shocks may be needed to get the patient's heart going again. The battery must not hamper the best possible patient care.
Most defibrillators are powered by nickel-cadmium. nickel-metal-hydride is also being used but there is concern of short service life. In a recent study, however, it was observed that a defibrillator battery cycles far less than expected. Instead of the anticipated 200 cycles after two years of seemingly heavy use, less than 60 cycles had been delivered on the battery examined. 'Smart' battery technology makes such information possible. With fewer cycles needed, the switch to higher energy-dense batteries becomes a practical alternative.
Sealed lead-acid batteries are often used to power defibrillators intended for standby mode. Although bulky and heavy, the Lead-acid has a low self-discharge and can be kept in prolonged ready mode without the need to recharge. Lead-acid performs well on high current spurts. During the rest periods the battery disperses the depleted acid concentrations back into the electrode plate. Lead-acid would not be suitable for a sustained high load.
The medical industry is moving towards lithium-ion. The robust and economical 18650 cells make this possible. The short but high current spurts needed for defibrillators are still a challenge. Paralleling the cells and adding current-limiting circuits that allow short spikes of high current will help overcome this hurdle.
http://batteryuniversity.com/learn/article/industrial_applications
kingworm
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now that is something to think about. i also would wonder about arcing the more powerful the batteries and the lower resistance of the coil builds. electricity is a funny thing until it paralyzes half your face
I'm not trying to be a smart ass BoomStick, but I have always used paralell in my mech boxes, and I understand paralell better. All of the above education flew over my head like a bird in high wind. Maybe if I took more time to really study and examine it, I might understand it. I want to do the safest and best way possible, I rather like my face the way it is, & so does my wife.....lol...No disrespect meant to you at all....instead, I give my utmost respect to those that know more than me about these things....
I prefer parallel myself. The super low resistances required for super high wattages when the voltage is only about 4 volts makes series something to consider. However, wanting to use an unregulated mod to vape over 100 watts is pushing the limits of safety and sanity in my humble opinion regardless of battery configuration. If a person doesn't thoroughly understand the science involved or the associated risks they shouldn't play with that kind of fire. My personal limits are 100watts for unregulated devices and 150watts for regulated devices. Adequate heating of multiple coils can easily be achieved within those ranges. Going beyond that is simply an attempt to show how big your dick is. There is a difference between high power vaping and being a dumbass. These are just my opinions.
And I agree with you 100%!
Haadkoe
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Not trying to argue with you, just pondering worst case scenario type possibilities here. Enough DC current can kill the shit out of you if not respected. Not saying our mods are going to kill us by electrocution, but I'm not saying that they absolutely couldn't either, especially when we're talking multiple cells in an unregulated enclosure.
3 charged high quality 18650's in series is 12.6v and 30amps, right? In your mouth. Totally absolutely safe under any and all circumstances? What if the dimwit puts the batteries in backwards and has a puff while soaking in the tub? Still safe? Lol
Ever hear about the guy who stuck pins in fingers on opposing hands to measure the resistance beneath the skin with a multimeter? Stupid, yes, and deadly... Also mostly irrelevant to our conversation, but fun to think about.
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Still applies.
Haadkoe
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The more I think about the subject, the more I realize boomstick is actually right about there being little to no danger of electrocution here, despite the fact that he is a prick.
To have any real danger of electrocution, the current would have to pass through your body which is quite unlikely in this application. The current would have to go from the positive on the battery, through your body, and return to the negative end of the battery. Since everything is self contained in a mod, it would be unlikely if not impossible to get yourself in the middle of that connection.
Unlike AC, which will take the path of least resistance to ground (which may be you), in DC applications the ground is the negative terminal on the battery itself, not actual "ground" like we think of in alternating current applications.
Of course I could be wrong here as well, but since the leading authority on electricity in this thread doesn't seem like spreading accurate information and would rather talk down to others as opposed to spreading knowledge, perhaps I'll never know.
To have any real danger of electrocution, the current would have to pass through your body which is quite unlikely in this application. The current would have to go from the positive on the battery, through your body, and return to the negative end of the battery. Since everything is self contained in a mod, it would be unlikely if not impossible to get yourself in the middle of that connection.
Unlike AC, which will take the path of least resistance to ground (which may be you), in DC applications the ground is the negative terminal on the battery itself, not actual "ground" like we think of in alternating current applications.
Of course I could be wrong here as well, but since the leading authority on electricity in this thread doesn't seem like spreading accurate information and would rather talk down to others as opposed to spreading knowledge, perhaps I'll never know.