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Problem with the Vamo?

Discussion in 'VAMO' started by Mindfield, Dec 19, 2012.

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  1. Mindfield

    Mindfield Vaping Master Verified Member ECF Veteran

    Aug 28, 2010
    Toronto, ON
    I think I've found a problem with the Vamo, and I'm curious if anyone else has experienced this.

    Now, this issue only occurs under specific conditions: With stacked 18350s in variable power mode with a low res carto.

    Here's what I think is happening: When in variable power mode, and you change cartos/atties/clearos with a different resistance, the Vamo seems to take about 0.5 to 0.75s to read the resistance of the device and set the voltage accordingly once it's gotten its reading. While it is reading the resistance it will use the last set voltage until it gets its reading and adjusts accordingly.

    Similarly, when you change batteries, upon firing the carto for the first time it will spend half to three quarters of a second reading the resistance before setting the voltage properly. However, because it does not remember any settings (other than whether you were in variable power or voltage mode, and the AVG/RMS mode) it has no last set voltage it can call on to use while it's getting a reading, so it seems to fire through the unregulated voltage of the battery until it has its reading, where it will then regulate the voltage to meet your set wattage.

    This is a problem.

    Let's take a less serious scenario. You're using an 18650 (or a single 18350 in mini mode). You're set to 10W with a 3ohm carto. That's 5.5V. No problem. Now you switch to a low res carto, 2ohms. For 0.5-0.75s, it's going to be testing that atomizer at 5.5V -- that's 15W. This is not necessarily catastrophic, but that's pretty damn hot and may scorch the juice while it's testing, so you may get a few puffs of slightly off-tasting juice until you vape past it.

    Now, if you're just changing to a fresh 18650 this is not a problem, as that first <1s test will only be pushing 4.2V unregulated at most -- 8.8W with a 2ohm carto, well inside acceptable levels.

    Now use stacked 18350s. Things get more serious.

    Fresh stacked 18350s inserted. 2ohm carto. Hit fire. For that first 0.5-0.75s on that first hit, the device is now blasting 35 watts through that carto. (8.4v unregulated through a 2ohm carto) Even for such a brief time, this is enough to damage or even pop coils. I've already damaged two SmokTech 2.2ohm single coil stubbies because of this. They didn't pop, but the first one saw its resistance drop to 1ohm, and the second to 1.5ohms (now 1.3ohms as I continue to use it -- might as well get what life I can out of it.)

    Even with a 3ohm carto that's still a brief blast at 23.5W. Possibly not enough to damage but not far enough away from that possibility for my liking.

    Has anyone else run across this issue? Because this thing should be using the lowest possible voltage when doing its resistance check, not allowing unregulated current through until it gets its bearings. But I wanna know if it's my device or if others have run across this.
     
  2. larktdl

    larktdl Super Member Verified Member ECF Veteran

    Oct 7, 2009
    Strathmore, AB
    Interesting observation ,,, Haven't detected this problem. I will test it out with a atty @ 1.8 ohms.
     
  3. Mindfield

    Mindfield Vaping Master Verified Member ECF Veteran

    Aug 28, 2010
    Toronto, ON
    I hope it's one you don't mind sending to its doom. :p Make sure you drip some liquid in there though, it should mitigate the sudden burst of power somewhat and you'll be able to sense the heat from the vapor if you try and take a drag. At least, for the brief time it lives, 'cos at 1.8ohms, if yours does the same as mine, that's nearly 40 watts -- in other words, it'll plink on like a light bulb and die pretty rapidly.
     
  4. larktdl

    larktdl Super Member Verified Member ECF Veteran

    Oct 7, 2009
    Strathmore, AB
    Single 18650 - no problems switching attys (both at different ohms), Vamo set at 10 watts (rms). Checked resistance of both attys and no change in resistance.

    Switched to stacked 18350s --- 1.8 ohm atty. By default the VW is 3 watts, hit fire button ----> it blew the coil. Checked the resistance of the coil --- 9.9 ohms.

    It appears that your observation is correct. Will build another coil and test to reconfirm.
     
  5. larktdl

    larktdl Super Member Verified Member ECF Veteran

    Oct 7, 2009
    Strathmore, AB
    I am using the Novas and rebuild them, so not an issue if things blow up !!!
     
  6. Mindfield

    Mindfield Vaping Master Verified Member ECF Veteran

    Aug 28, 2010
    Toronto, ON
    Good -- probably the best way to test them. I'd test it on one of my RBAs but I'm at work right now. If you don't try it out before I do though I may give that a go this evening.
     
  7. X P3 Flight Engineer

    X P3 Flight Engineer Ultra Member Verified Member ECF Veteran

    Feb 27, 2012
    Moncton, N.B. Canada
    What would you suggest as a "work around" for this?

    Would setting a lower wattage before changing devices prevent it from starting at too high of a voltage?
     
  8. larktdl

    larktdl Super Member Verified Member ECF Veteran

    Oct 7, 2009
    Strathmore, AB
    I did a couple of tests and can confirm the observation by Mindfield.

    I did two tests ... the first atty metered at 2.1 - 2. 3 ohms. The problem did not replicate.
    I repeated again using atty metering at 1.8 - 1.9 ohms. The coil blew up.

    I will add that I never noticed this problem before because I don't normally use LR attys and I always check the resistance & power setting on insertion of fresh batteries, power on/off cycle and when I change atomizers.
     
  9. larktdl

    larktdl Super Member Verified Member ECF Veteran

    Oct 7, 2009
    Strathmore, AB
    This is why we need people like Mindfield in the vaping community ,,,, I would never have detected this as a problem: I would have just attributed the problem to a crappy coil and not a device specific problem.
     
  10. tc1

    tc1 Ultra Member Verified Member ECF Veteran

    Oct 26, 2011
    Ohio
    Are you guys confirming this issue with any meters or scopes?

    35 watts should be impossible to achieve.
     
  11. Mindfield

    Mindfield Vaping Master Verified Member ECF Veteran

    Aug 28, 2010
    Toronto, ON
    Unfortunately the wattage setting doesn't get involved with this problem, because on first insertion of the battery (possibly on power-up too when you 5-click it on) when it does its ohm test while in variable wattage mode, it's sending unregulated current straight through; the regulation doesn't kick in 'til it has metered the carto.

    So just to be clear, this problem does not happen in variable voltage mode as far as I know, and while it does happen in variable wattage mode with 1x18650 or 1x18350 the problem isn't an issue because the unregulated voltage of a single battery is low enough that it isn't going to blow any coils.

    I don't know of any workaround other than to avoid using it in stacked mode or, if you do, use HV atties and cartos (>4ohm) or RBAs with large gauge wire or lots of wraps that can take that kind of current.

    Thanks. :) I only noticed it because I wanted to test in stacked mode, and I was using a glass tank with LR SmokTech cartos in it in variable wattage mode (the entire reason I bought the Vamo). First vape I took with fresh batteries was hot for a moment and then seemed to die off. Test the resistance, and yep ... it's dropped to less than half what it should be. Try again with another carto, same crap, only it didn't drop quite as far (1.5ohms) so it's still usable, at least 'til it drops below 1.2.

    Shame too, 'cos it's more efficient in stacked mode (it only has to limit power, not boost it, so the boost circuit doesn't suck down any power) but I'm not touching it in stacked mode now.

    Thanks for confirming my findings, now I know it's not just me.
     
  12. Mindfield

    Mindfield Vaping Master Verified Member ECF Veteran

    Aug 28, 2010
    Toronto, ON
    Not at all. Stick two freshly charged 18350s in a Silver Bullet, screw on a 2ohm carto, and press the button. Instant 35 watt vape. For about a second.

    I don't have a meter that can test under load though -- I'd have to cobble together a 510-510 adapter of sorts with metering leads.
     
  13. tc1

    tc1 Ultra Member Verified Member ECF Veteran

    Oct 26, 2011
    Ohio
    Given the load test reviews of the vamo I just find those numbers hard to believe.

    On a fully charged 18650 load tests have shown max watt output at around 11 amps. That's a limitation of the battery itself.

    I mean ... at 6 volts and a 5 amp limit you can't even get to 35 watts. Its mathematicaly impossible.
     
  14. Mindfield

    Mindfield Vaping Master Verified Member ECF Veteran

    Aug 28, 2010
    Toronto, ON
    Did you mean 11 amps or 11 watts? Because 11 watts is nothing to an IMR. 11 watts on a 2ohm carto is only 4.7V and a 2.3A draw. Now, if you're talking 11 amps (which is slightly beyond the rated 10C output of an AW IMR 18650) then ... 35 watts is still a walk in the park. 8.4V through a 2ohm device (35W) still only draws 4.2A. Not even half what an IMR is capable of delivering.
     
  15. tc1

    tc1 Ultra Member Verified Member ECF Veteran

    Oct 26, 2011
    Ohio
    I was talking watts.

    3 seperate reviewers have tried load tests with low resistance and none of them could get it to fire above 11-11.5 watts in vw mode using an 18650.

    If there was an intense spike as suggested, id expect them to see that on their oscilloscopes.
     
  16. Mindfield

    Mindfield Vaping Master Verified Member ECF Veteran

    Aug 28, 2010
    Toronto, ON
    This is not under normal use circumstances though. This only occurs under one specific set of circumstances:

    When,

    A) Using two 18350s in stacked mode,
    B) Set to variable wattage mode,
    C) After inserting the batteries (or possibly when turning back on when you've 5-clicked it off), and,
    D) Upon firing the carto for the first time

    In this specific circumstance, the Vamo appears to perform its initial resistance test on the carto, it sends completely unregulated current through the carto until it gets the resistance and the regulation kicks in to drop the voltage to a level appropriate to your wattage setting. The unregulated burst only occurs once (upon first turning on or inserting batteries) and only for 0.5-0.75s.

    Note that this happens in non-stacked mode too (single 18650 or 18350 mode) but since the unregulated voltage of a single battery is comparatively low (4.2V), this is not going to cause any problems even with the lowest res cartos. It is only the unregulated voltage of two stacked 18350s in parallel that causes problems because its unregulated output voltage is 8.4V, which is at least twice what a LR carto is designed to handle.

    Note that it also does happen in a similar, but less risky fashion, in either stacked or single mode when switching atomizers as well. When switching atomizers, it will use the last voltage that was set during its initial resistance check before changing the voltage to the new setting (if the device attached has a different resistance than the last one). This is not a huge problem unless you're going from a high resistance device (>3ohm) to a very low resistance device (1.5-2ohm) -- even then it may not be a big issue but it could still cause some slight problems.

    Ideally the Vamo should perform its initial resistance check at 3V, no exceptions, regardless of battery configuration or previous voltage setting.
     
  17. larktdl

    larktdl Super Member Verified Member ECF Veteran

    Oct 7, 2009
    Strathmore, AB
    Well one thing is for sure ,,,, the device is blowing up LR attys in stacked battery configuration. Confirmed by 2 so far. Don't get me wrong here, I am not going to stop using the Vamo, it is a very good mod and I am still on the Vamo band wagon.

    This problem is something people need to consider before purchasing it especially if that person exclusively intends to use it with stacked 18350s and LR attys.

    Ultimately, the manufacturer should address the issue in the next release.
     
  18. tc1

    tc1 Ultra Member Verified Member ECF Veteran

    Oct 26, 2011
    Ohio
    Try switching to a below 1.2 ohm device and let me know if it fires at all.

    This should tell us if there indeed a problem.
     
  19. larktdl

    larktdl Super Member Verified Member ECF Veteran

    Oct 7, 2009
    Strathmore, AB
    Explain please ???
     
  20. tc1

    tc1 Ultra Member Verified Member ECF Veteran

    Oct 26, 2011
    Ohio
    Because if the vamo is firing based on the last resistance for a second ... technically it should fire a sub 1.2 ohm coil for a second as well.
     
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