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Coil build/battery suggestions

Discussion in 'Cloud Chasers' started by Juan Vazquez, May 14, 2015.

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  1. Juan Vazquez

    Juan Vazquez Full Member

    May 2, 2015
    Hey so I've been wanting to go lower on my ohms. Lowest I've gone is .16 on my mech mod. Just wondering what are some good builds and what wire you use. I'm also wondering what are some good batteries to use. I'm currently using subohmcells which are 2800 mah, 35 amps
     
  2. KenD

    KenD Vaping Master ECF Veteran

    Aug 20, 2013
    Stockholm, Sweden
    .16 is pretty much the lowest you can "safely" go on a mech. There are no batteries that have a higher cdr than 30 amps. All 35 amp batteries I've come across are rewrapped batteries with overstated amp ratings, usually 20 amp cdr under the wrapper (making a .16 ohm coil unsafe).
     
  3. ghost_92

    ghost_92 Full Member

    May 12, 2015
    Efest 35. I build .12 all the time. I've always just used the pulse rating. I don't know anyone that can rip a hot build longer than 10-15 seconds which is where the constant amp rating would come into play.
     
  4. KenD

    KenD Vaping Master ECF Veteran

    Aug 20, 2013
    Stockholm, Sweden
    There's no standardization when it comes to pulse ratings, and those numbers are rarely something that manufacturers have put out. Particularly with Efests and other rewrapped batteries where you don't know what's under the wrapper. Dangerous. You might drink and drive all the time without problem, until something bad happens. Why take the risk?
     
  5. Juan Vazquez

    Juan Vazquez Full Member

    May 2, 2015
    I've used efest and subohmcells and gone down to a .12 though
     
  6. notactuallyluke

    notactuallyluke Full Member

    May 8, 2015
    It's not that it can't be done. It's just extremely dangerous. Especially on a mech. I wouldn't expect see anyone around here advising you to build anything that low.
     
    • Like Like x 1
  7. Juan Vazquez

    Juan Vazquez Full Member

    May 2, 2015
    Yeah of course, while I was vaping that build I put it on my unregulated box mod. 2 parallel 18650s
     
  8. ghost_92

    ghost_92 Full Member

    May 12, 2015
    Authentic efest directly from the manufacturer. Wasn't advising him to go out and do it. I was simply saying I'VE done it. With no issues. The pulse rating would be 35. It has a constant rate of 20amps.
     
  9. KenD

    KenD Vaping Master ECF Veteran

    Aug 20, 2013
    Stockholm, Sweden
    Question: what, specifically, does a "pulse" amount to? How long is it, and how long of a pause do you need to have between pulses? Where do you find reliable information on that, and do you keep track of the different definitions for all your different batteries?
     
  10. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

    Supporting member
    May 13, 2015
    Unfortunately, the answers to those great questions are complicated. I'm a vaping noob but have been spec'ing cells and designing power supplies, battery chargers, battery management/protection systems, battery dischargers, and other related devices since 1992. Here's my take....

    A "pulse" can be anywhere from microseconds to seconds long. It all depends on the industry and application where the cells are being used and what the parties involved define a pulse as. Vaping definitely is on the long end of the range of what is considered a pulse and may be considerably longer than what the cell manufacturer or reseller considers to be a pulse.

    To make things worse, a pulse rating is not a firm specification on its own. It is tied to duty cycle, cell life, ambient temperature, and other factors.

    As you mentioned, the rest time between pulses is important. It allows the heat that has built up inside the cell to migrate outwards. This evens out the internal temperature of the cell, eliminating damaging hotspots, and lets the cell cool. The duty cycle, or ratio of the pulse on time to the off time, is extremely important and has to be part of any pulse current rating. For example, one 4 second pulse every minute might not be a problem at all. But, one 4 second pulse every 5 seconds might easily cause the cell to overheat and vent (or worse).

    Cell life can also be affected by the pulse rating. A cell might have a pulse rating of 30A but how much does that effect cell life? Cell manufacturers are typically very conservative in their ratings but resellers often aren't. A cell could easily be spec'ed anywhere from 10A to 30A pulse, depending on how long the person who is rating the cell wants it to last. An application that draws 10A pulses might result in a cell that last 500 cycles. An application that draws 30A pulses could shorten that to 150 cycles.

    Bottom line...you need to know the other related data to judge whether a cell has the spec rating you need. You'll never get that from the manufacturer or, most likely, the reseller. Due to all the variables, the manufacturer will always say that you need to test their cells in the application you're considering. They can only give you their nominal specs, listed in the data sheet. And the reseller typically just doen't have the time to test all their cells for all the different uses those cells might see. Third party testing is typically how you find the info we need to judge whether a cell will perform the way we want for a particular vaping setup. Other enthusiasts often post their cell test results and sometimes the results can be directly applied to your application. Sometimes you have to piece together results from several different tests to extrapolate how the cells might behave for you. <deep sigh> It's often very tough to do!

    To simplify keeping track of all this info, I'll settle on just one cell make/model for each broad application I need them for. I note their max ratings (from my own testing) and just use the best cell for any new application that pops up. Doing your own testing is a great option if you have the time. The West Mountain Radio CBA IV Pro battery analyzer is a fantastic device to test cells with. It has highr ratings but I recommend 100W/30A maximum for long device life. I have several constant-current electronic loads (battery dischargers) here that I have designed but so often turn to the CBA for a quick test because of its convenience and ability to store and later review the discharge graphs it produces (voltage vs time, Amp-hours, etc.).

    [edit] another important pulse-related rating is how much does the cell temperature rise for the pulse? The rating is almost useless without this information. If the cell rises to 80C case temperature for a certain pulse, cell life will really suffer. However, if max case temp is 40C after the pulse, then no problem. Remember though that cells used for vaping are sealed in a box/tube and cool very slowly. We cannot just keep pulsing them at their max rating without taking into account heat buildup. You need to derate the cell's pulse rating based on the duty cycle, i.e., how often you draw. By how much? Unfortunately you need to test, test, test.
     
  11. Martnargh

    Martnargh Senior Member ECF Veteran

    Feb 26, 2015
    Miami
    Just get dome vtc4s from lightningvapes
    [​IMG]
     
  12. edyle

    edyle ECF Guru Verified Member ECF Veteran

    pulse rating.

    one of the important applications of lithium batteries is in remote control vehicles with electric motors.
    With an electric motor (similar to the starter motor in a car), the motor has a low resistance, and draws a very high current from the battery but only for a fraction of a second. Once the motor starts turning there is no longer a high current.
     
  13. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

    Supporting member
    May 13, 2015
    That's more like it!
    I suspect that there's a typo for the <3sec rating but probably about 125A. Do they mention cell temperature or duty cycle?
     
  14. KenD

    KenD Vaping Master ECF Veteran

    Aug 20, 2013
    Stockholm, Sweden
    All those problems you listed are my point. Pulse ratings are simply things one shouldn't go by. There's really no point in pushing batteries for more than they can handle. If one cannot get massive clouds at .21 (higher really, but let's go with the limit of the most common high quality batteries we use) it's time to learn to build and wick better. If that's not enough, there are two and three battery regulated mods that can provide wattages that mechs just can't.
     
    • Like Like x 1
  15. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

    Supporting member
    May 13, 2015
    One of the better ways to compare cells in high-current applications is to check the internal resistance (IR) specs. The DC spec, not AC. This is the primary cause of cell heating which is a big factor in determining the pulse rating, which most manufacturers don't do...too many variables. Best for each customer for the cells to test in their commercial/industrial application.

    The IR spec is also what determines the cell's voltage under load. At high current levels we can't use 3.6-3.7V as the cell voltage in our power calculations. The cell(s) could be running at 3.3V, 3.1V, or even lower.

    Finding out what the IR spec actually is though can sometimes be a challenge. It's easy to see why many cells get just two specs for current (CDR and pulse). And for many users that's fine. The problems start when a user actually wants to run their cells anywhere near the max ratings. Usually it all turns out OK. Perhaps shortened cell life but that's often a tradeoff users will accept. Occasionally, it doesn't turn out OK though.
     
  16. sonicbomb

    sonicbomb Vaping Master Verified Member ECF Veteran

    Feb 17, 2015
    1187 Hundertwasser
    The issue of battery safety comes up again and again. For simplicity's sake imagine two zones, one red, one green. What ECF most experienced users advise is stay within the CDR of a given battery. This places you within the green zone. Anything above this number of amps is in the red zone.
    You may get away with it without consequence, or might get hurt. Maybe only a trashed mod, maybe 1st degree burns or worse. The choice is ultimately your yours, we just would like you to be safe doing what is is after all a recreational activity.
     
  17. ghost_92

    ghost_92 Full Member

    May 12, 2015
    I'm sorry for stirring this up. I guess I'm just a little too crazy for this sites building forums. I had an electrical engineer explain it to me. I guess I trust him with my hands?
     
  18. Juan Vazquez

    Juan Vazquez Full Member

    May 2, 2015
    You say .21 so then why are there guys (in competitions) using different wires other than kanthal and going way lower with the exact same build? Cause I'm currently trying to start doing competitions.
     
  19. KenD

    KenD Vaping Master ECF Veteran

    Aug 20, 2013
    Stockholm, Sweden
    Because they're stupid
     
    • Like Like x 1
  20. Martnargh

    Martnargh Senior Member ECF Veteran

    Feb 26, 2015
    Miami
    you need a bunch of batteries to go that low. Those comp guys hit it once or twice then switch batteries to minimize stress in the cells.
    When i used to ride with my mechs it was normal to carry a couple of battery cases with me.
    Now i pretty much only use my hexohm which allows me to build closer to.3 and blow clouds waaaaaaay bigger than what you see in those comps, thats why anything but mechs are not allowed in comps.
    For the record those comps are pretty overrated imo. You gotta use house juice, which either has no flavor or tastes like garbage. Plus a blast of vape at <.1ohm is extremely hot with very little reward in return.
     
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