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Need a little help with a mech build :)

Discussion in 'Coil Builds' started by Lewbuh, Oct 7, 2019.

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  1. Lewbuh

    Lewbuh Full Member

    Sep 30, 2019
    Hey all!

    Recently got a Kennedy vindicator 21700, done a lot of research on ohms law and battery safety. But I just wanted to make sure the coils I’m about to use with a Samsung 30T are going to be safe with this, only ever used 18650 mechs. I’ll post the coil stats below from the site I got them off.

    Thanks :)

    Core: Three Pieces of 26g Wire Buddha Nichrome 80

    Alien Fuse: 36g Wire Buddha Nichrome 80

    Wraps: 5

    Inner Diameter: 3mm

    Pre Pulse Resistances

    Single Coil Resistance: 0.14

    Dual Coil Resistance: 0.07

    Post Pulse Resistances

    Single Coil Resistance: 0.22

    Dual Coil Resistance: 0.11
     
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  2. Lewbuh

    Lewbuh Full Member

    Sep 30, 2019
    Oops forgot to mention I’ll be running the coils dual on a Kennedy 25 :)
     
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  3. greek mule

    greek mule Ultra Member ECF Veteran

    Feb 2, 2018
    Athens,Greece
    This question kinda implies that you are not familiar with the operation of a mechanical mod and battery safety.

    Before you use that build you should know that it is pulling 38 ampers from your battery(at full charge-4.2V).
    I=V/R=4.2/0.11=38A

    You also should check what is Samsung 30T's truth CDR,which actually is 35 A.
    List of Battery Tests | E-Cigarette Forum

    Start with a higher ohm build, 0.2 or 0.15 ohm,always check your atty(with the top cap on) on a regulated device or an ohm meter for shorts before you fire it on a mech.

    After you get more experienced you can safely build a bit lower like say 0.12 ohm.(Depending on battery's CDR).

    Explain it to the Vape Noob: Ohm's Law Calculations for a Mechanical Mod

    Baditude's guide for your first mech mod

    Battery safety
     
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  4. greek mule

    greek mule Ultra Member ECF Veteran

    Feb 2, 2018
    Athens,Greece
    The coils you mentioned come out at 450 mg each.This is a huge mass for a single battery mech.You have to expect long ramp up considering the initial voltage drop of the battery at 38 ampers pull.

    You may consult Steam Engine if you are interested in making your own coils that have the proper ohms/mass for a mech.
     
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  5. bombastinator

    bombastinator ECF Guru Verified Member ECF Veteran

    Sep 12, 2010
    MN USA
    Without looking at the math my gut reaction is I personally would consider running it single coil but not dual coil. .11 is just too low for me. Wire resistance can fluctuate a bit, and the lower you go the higher a percentage a couple hundredths of an ohm can be. As you approach 0 ohm fractional fluctuations get larger and meters get less accurate. Even if it reads .11 cold I wouldn’t be surprised if it drops to .08 when it heats up. Also it’s really high mass so it’s going to be a hot vape and it’s going to ramp slowly.

    This has “not so great an idea” written all over it. Especially with original pre burn in numbers like you got. My move would be to toss both coils and build again. Wire is cheap. Faces are expensive.
     
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  6. Lewbuh

    Lewbuh Full Member

    Sep 30, 2019
    Thank you so much, I think I may have just been taught wrong by the guy in the vape store I used to go to, he always said I could got around 5amps over the CDR and not have any issues.

    Had a read through the explain it to the vape noob post and it’s really useful.

    I was thinking of picking up some Nichrome aliens which are 3-28/36g 6 wrap 2.5mm .17Ω. If I’ve understood the post correctly these should draw 24.7 amps and be safe to use right ?
     
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  7. bombastinator

    bombastinator ECF Guru Verified Member ECF Veteran

    Sep 12, 2010
    MN USA
    Not IMHO. The problem is you’re still too close to 0 ohm. The numbers might technically work out to .17 but that doesn’t mean it will actually BE .17 when it heats up. At the levels you’re dealing with serious accuracy starts to matter a lot. Microscopic imperfections in the wire start to matter.
     
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  8. Lewbuh

    Lewbuh Full Member

    Sep 30, 2019
    Thanks man, I’ve decided not to use them after reading through the posts Greek mule sent me.

    Trying to build around 1.7 but I keep messing it up, was looking at some m terk Nichrome aliens which are 1.7 and I may just get them.
     
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  9. icepickmaker84

    icepickmaker84 Moved On ECF Veteran

    Feb 7, 2019
    Indiana
    If the fella at the vape shop told me that I wouldn’t leave until he put something in his rda that pushed his battery 5amps over its cdr...I’d also have a fire extinguisher handy lol. Me personally I try to leave 5 amps of headroom so if my battery is 35a I’m not going over 30a.
     
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  10. greek mule

    greek mule Ultra Member ECF Veteran

    Feb 2, 2018
    Athens,Greece
    Is this your first hybrid mech?
     
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  11. Lewbuh

    Lewbuh Full Member

    Sep 30, 2019
    No, I used a vgod elite mech for a while and a Tauren mech. I don’t build my own coils on mechs though, I buy them pre made.
     
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  12. bombastinator

    bombastinator ECF Guru Verified Member ECF Veteran

    Sep 12, 2010
    MN USA
    My personal absolute minimum is to keep it above 0.2 ohm. There are various coil calculation apps which should help you a lot.
     
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  13. Lewbuh

    Lewbuh Full Member

    Sep 30, 2019
    Okay thanks, would you by any chance be able to recommend any pre built coils around 2 ohms? Really struggling to find them with that reading.
     
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  14. greek mule

    greek mule Ultra Member ECF Veteran

    Feb 2, 2018
    Athens,Greece
    Correct.These are fine coils to get the job done.
    Though i'd prefer 3 mm inner diameter for the kennedy 25.
     
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  15. bombastinator

    bombastinator ECF Guru Verified Member ECF Veteran

    Sep 12, 2010
    MN USA
    Premade helps a bit but not enough. There’s always a bit of variance in the actual resistance of a coil. Pro coil builders measure their wire and (one hopes) measures the ohm ratings on the coils they make but even then there are variances. And the amount of raw variance does not go down as one approaches fractional ohms, so the actual amount of variance effectively goes up.
     
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  16. Lewbuh

    Lewbuh Full Member

    Sep 30, 2019
    Okay thanks, I normally use 3mm inner diameter too but I can’t really find any around the 2 ohm mark
     
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  17. bombastinator

    bombastinator ECF Guru Verified Member ECF Veteran

    Sep 12, 2010
    MN USA
    A pair of 2ohm coils would be 1.0 ohm. The problem you’ve got is you get higher ohms with longer thinner wire. Multiplying wires reduces ohms. You seem to be looking for exotic coils which are generally multiple wire, and thin wires burn out quickly. If you can find even two 1.0 exotics they’re going to be kinda long and fairly thin. Good chance they won’t fit in your atty. I have only ever bought premade coils once, so I’m little help I’m afraid.
     
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  18. Lewbuh

    Lewbuh Full Member

    Sep 30, 2019
    Yeah I’ve always been a big fan of alien builds. Guess I’ll just whip up a 0.2 ohm round wire kanthal build for now, I know I can do that and it will be safe. Thanks for all your advise :)
     
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  19. greek mule

    greek mule Ultra Member ECF Veteran

    Feb 2, 2018
    Athens,Greece
    We just want to be safe.Take care.
     
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  20. bombastinator

    bombastinator ECF Guru Verified Member ECF Veteran

    Sep 12, 2010
    MN USA
    You may get better advice in the mech specific forum section. They deal with this stuff all the time. I took my leave of mech problems years ago when good regulated mods came out. @Baditude is also very knowledgeable. Moreso than me.
    @Don29palms is one mech user that comes to mind off hand as well. He and I differ drastically on politics and mech safety but the man knows mechs.
     
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