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how to calculate lipo wattage?

Discussion in 'Battery Junkies / Chargers' started by mokeife, Nov 12, 2016.

  1. mokeife

    mokeife Bronze Contributor

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    just got a 4s pwm lipo and havnt really cranked it up yet because i havnt figured out how to calculate my wattage or amperage so ive kept the potentiometer down pretty low where i know i am safe. this is how i thought it was done. my potentiometer is set to 30 percent so 30 percent of 16.8 volts is 5.04 so i plug 5.04 into the calculator. the next figure i know is my resistance which is .36. now when i plug these in i come up with only 14 amps and 70.56 watts which i know is not right since this is a heavy 10 wrap twisted 24 build in a 30mm rda and its a warm vape. can someone please point me in the right direction? thanks
     
    Last edited: Nov 13, 2016
  2. Gregjl

    Gregjl Bronze Contributor Member For 1 Year

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    There are ohms calculators online you can use and you only need to enter two values and it figures out the rest for you also there is an app that you can use where you pick out every detail of the build (they show you photos of coils and you touch the one you made) what gauge how many wraps etc. And then of course there's using a meter. Hope that helps. My app is called vape tool.
     
  3. mokeife

    mokeife Bronze Contributor

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    i used one of those ohms law calculators to figure that out however i know that its not right do i have to multiple then70.56 by 4 since there are 4 cells?
     
  4. mokeife

    mokeife Bronze Contributor

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    dammit sorry i posted that so many times my computer froze and i didnt think it went through
     
  5. Zamazam

    Zamazam Evil Vulcan's do it with Logic Staff Member Senior Moderator VU Donator Platinum Contributor Member For 3 Years

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    fixed.
     
  6. mokeife

    mokeife Bronze Contributor

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    thanks
     
  7. Gregjl

    Gregjl Bronze Contributor Member For 1 Year

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    I don't want this to be the final word because I'm new too, but I don't think so. Volts are volts the coil doesn't care if you have a lipo, nimh, or liion. It's the coils that have the value change when you add a coil or take away. There's an "ask an expert" section here
     
  8. mokeife

    mokeife Bronze Contributor

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    thanks ill try there
     
  9. Zamazam

    Zamazam Evil Vulcan's do it with Logic Staff Member Senior Moderator VU Donator Platinum Contributor Member For 3 Years

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    I'll move the thread to battery junkies.
     
  10. mokeife

    mokeife Bronze Contributor

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    i already reposted it you can delete it if youd like
     
  11. Zamazam

    Zamazam Evil Vulcan's do it with Logic Staff Member Senior Moderator VU Donator Platinum Contributor Member For 3 Years

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    It got zapped as a duplicate already
     
  12. Vapescaped

    Vapescaped New Member ECF Refugee

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    Well, there are a couple ways I've seen lipo pwms run, and it looks like this:
    The way you have it would be right IF the potentiometer (cant spell) actually limits the voltage by only opening the mosfet partially, to allow a smaller current to flow through it, hence, lower voltage.
    But the more common way I've seen it done, and probably the way you have in yours is that the actual voltage is at full power, but you control the duty cycle(the time the power is applied to the atomizer) So, 30% duty cycle would mean you are vaping 16.8 volts across .38 ohms for a total of 742.736842 watts, But only 30% of the time. You could say 30% of 742 watts is 222.6 watts, but it really doesn't work that way. It might feel that way, I don't know because I never tried it
    These pwms pulse at an adjustable rate(by the potentiometer). so by adjusting the pot, you're just supplying that poer more or less of the time. But it's the same power regardless.
    If your device has a volt meter built in that changes with the pot, you could have it the way you described in your calculations, but still highly unlikely. But those voltage meters measure RMS, not really an instant reading, so you can have those read some baffling numbers when you chuck clouds. Thats why a lot of box builders have it to measure battery voltage only(and because you can throw a 3s lipo in it and still know when your battery needs charging)
    I hope some of this helps. I had my first PWM back in 2011, and I got it all wrong explaining it, but never took it dow. But just for kicks, heres the video:
     
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  13. mokeife

    mokeife Bronze Contributor

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    thank you for that i couldnt find anything online
     
  14. mokeife

    mokeife Bronze Contributor

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    do lipos hit just as hard when the battery is low as opposed to full? it seems that way and when i throw my volt meter on and press the fire button it reads a constant voltage no matter how low the cells are
     
  15. Vapescaped

    Vapescaped New Member ECF Refugee

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    They shouldn't. As voltage drops in the lipo, the final voltage output should drop with it. Unless it is somehow regulated, but I'm not sure if a regulator exists that can handle that much power. Thats a really powerful mod though so you might not notice. and accurate voltage readings on a pen are tough to get, like I said.
    Can you throw a 24mm rda on that 3s lipo or will it be too hot?
     
  16. mokeife

    mokeife Bronze Contributor

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    i might be able to get away with a 24mm rda however i dont have one to try. and its a 4s lipo so it might be too hot. and isnt it regulated in a way because it has a potentiometer?
     
  17. Vapescaped

    Vapescaped New Member ECF Refugee

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    It is not really regulated by voltage with a pulse with modular what happens is the pwm pulses on and off really fast and you can adjust the speed of the pulses by turning the potentiometer. If you turn up the potentiometer it makes the pulse is wider so if you say run 30% just throwing numbers out there that would mean that when you press the button 30% of the time you're holding the button it is actually supplying power. The power that's being supplied is usually just straight battery power. That operation is formed from what is called a 555 timer. If I can find a good YouTube video to send a link I will when I get home. But the power going to the atomizer is usually unregulated battery power just turned on and off really fast like a pulse and you can adjust the frequency of the pulses.
     
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  18. Vapescaped

    Vapescaped New Member ECF Refugee

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    heres a good video that explains how a PWM works, especially the first few minutes. Notice the square voltage output in the duty cycle. Thats why it can read 5 volts on your meter and still power those massive coils. Because it's machine-gunning (around)16 volts to those coils. And you control how many punches of full voltage per second you are delivering to it by changing the duty cycle, which he shows on the correct tool to measure it, an ociliscope, around the 9 minute mark, I think.
    I should really start a blog about all this stuff, because it almost seems like the ones who know about them are all making them and don't have time to explain it all. Anyways, hope this helps:
     
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  19. mokeife

    mokeife Bronze Contributor

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    just curious i have a multimeter is there a way to measure the wattage with that?
     
  20. Vapescaped

    Vapescaped New Member ECF Refugee

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    well, no, not with a multimeter. Wattage is calculated by multiplying current times voltage. current is calculated by voltage divieded by resistance. Ohms law is the law. Even if there are a bunch of components in the system that give you weird answers, ohms law always applies.
     
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  21. mokeife

    mokeife Bronze Contributor

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    which voltage do i use. when i screw the voltage meter on at lets say 30 percent on the potentiometer it give me a reading 0f 9.66 then when i screw the tank on the volt meter it gives a reading of 4.19. so which reading do i plug in to find my wattage. because if i plug in my resistance and 5 volts it only comes out to 70 watts and this is more like a 250 watt build
     
    Last edited: Nov 22, 2016
  22. Vapescaped

    Vapescaped New Member ECF Refugee

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    If you go over to the mudder's section, under general mod builders, I have a full article written up that explains how your pwm mod works. Basically, if you have a pwm, you are running full power, just controlling the amount of time you are applying that power.
    http://vapingunderground.com/threads/building-your-own-lipo-mod-part-3-pwm.289636/
     
  23. mokeife

    mokeife Bronze Contributor

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    i skimmed through that article and it had alot of good information in it but i understand how a pwm works however im still a little confused on how to calculate my wattage and amperage
     
  24. Vapescaped

    Vapescaped New Member ECF Refugee

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    It's full wattage, full amperage. So it's 855 watts, all the time. You only slow down the pulses, not change the voltage applied
     
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  25. mokeife

    mokeife Bronze Contributor

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    ok thanks but how do i figure out the pulsed wattage? and how come i see people on youtube saying their vaping 2000 watts are they full of shit or do they have a different mod than i do? it looks like their using 4s lipos i just dont know how they get 2000 watts out of them not that i wanna vape that high im just curious
     
  26. Vapescaped

    Vapescaped New Member ECF Refugee

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    They might have a different build.
    Voltage times resistance equals amperage.
    Voltage times amperage equals wattage.
    A lower ohm build will give you more amps, which will give you more amperage. Just make sure you don't exceed the minimum resistance your manufacturer calls for.
     
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  27. mokeife

    mokeife Bronze Contributor

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    do i just take 30 percent of 855 and thats my pulsed wattage? "You could say 30% of 742 watts is 222.6 watts, but it really doesn't work that way" you said that in an earlier post if it does work that way then how doesn't it work?
     
    Last edited: Nov 23, 2016
  28. Vapescaped

    Vapescaped New Member ECF Refugee

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    T
    That would be your average wattage, but really 855 watts is being applied every time you fire, just for different amounts of time as you adjust the potentiometer
     
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  29. mokeife

    mokeife Bronze Contributor

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    just got a modfather tank and so far i love it however i cant fit a very big clapton build in it i put as many wraps of staple staggered fused clapton as i could and that would be 5 wraps and ohms out to .17. and when i calculated my wattage it comes out to 1660 watts. i have my potentiometer set at 20%. so i took 20% of 1660 watts and came up with 332 watts and im sure that my watage is lower than that. and a second question does anyone know if thats a safe build for this cell i think it is just wanted to make sure thanks ps. the battery is a 2200mah 4s lipo c rating is 45-90c
     
  30. Vapescaped

    Vapescaped New Member ECF Refugee

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    Well, again, it is drawing 1660 watts from the battery. But it's like you are pressing the fire button multiple times while you inhale instead of just holding it down.
    I recommend talking to the manufacturer of your mod to see if the resistance is ok, because a lot of them recommend that you don't go past .2 or.3 ohms. The best way to see if the battery can handle the draw is to use it at a faster pace for 5-10 puffs, then immediately feel the battery, if it feels warm, it's probably too much of a draw on the battery. But seriously, contact the manufacturer for ohm ratings because the MOSFET, the chip that actually switches on and off the power, might not be rated for such a heavy amperage draw. Better safe than broken
     
  31. mokeife

    mokeife Bronze Contributor

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    the guy in the vape shop that sold it to me always had low ohm builds in his but i will contact someone to make sure and were my calculations correct because this seems alot less than 300 something watts i understand that it pulses at 16.8 volts
     
  32. Vapescaped

    Vapescaped New Member ECF Refugee

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    Well
    Well, no. It's still 1660 watts. The battery is still putting out 16.8 volts, and the ohms are still .17. it gets calculated just like any other device because of ohms law. The 300 or so watts is a "feels like" wattage. But for battery safety reasons, you need to know that your actual amperage draw does not change with the potentiometer. It sounds like the mod builders made a high draw device, but if it wasn't, you could blow up the. Battery, even with the potentiometer set at 0 if you put in too low of a resistance.
    Sorry for being stuck in this loop, but I must express my concern over battery safety, because that battery faces the same draw no matter where you set the potentiometer. Only by adding a higher resistance coil do you ease the strain on the battery in a pwm setup.
     
  33. mokeife

    mokeife Bronze Contributor

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    thanks for that im starting to get a grasp of this however it doesnt "feel" like 300 watts it feel more like 200 maby less thats why im a little confused
     
  34. Vapescaped

    Vapescaped New Member ECF Refugee

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    I was too when I watched a video and the guy was firing massive coils at 4 volts. I called bs on it and researched the crap out of it. The best analogy I can explain is if you took a mod and set the watts. Then took a long press draw. Then take that exact same setup and instead of a long press draw, push that fire button multiple times in a single draw. It feels like less watts. But you didn't change the wattage. You only changed how long the device was firing while you were drawing.
     
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  35. mokeife

    mokeife Bronze Contributor

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    i understand the pulsing i just dont know how to calculate what the wattage feels like
     
  36. Vapescaped

    Vapescaped New Member ECF Refugee

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    There really isn't any way to calculate the "feels like" except for the average voltage method you were using. But as you can see, that way gives you some really weird answers. Comparing a pwm to other devices is an apples to oranges comparison.
     
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  37. Wheelin247

    Wheelin247 New Member

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    I know this thread is a little old but I figured I'd post this comment anyways. Here is a website I use.

    http://www.kritikalmass.net/battery-calculator/index.php

    So you will plug in the mAh of the lipo your using and then plug in the C rating (continuous discharge) of the lipo. That will give you the amps that your battery should be putting out. Then you will go down to the next section and plug in the resistance of the atty and the volts of your battery and that will give you the amperage and the wattage that your device is putting out if you have the pot set to 100%.

    Hopefully this is what you were looking for even though you have probably found out how to figure the wattage by now. I mean I'm posting this 7 months after the last comment in the thread. Lol.
     

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