"voltage drop" rant

[ukeman]

the first question is a little more difficult; K Tech and i were bouncing around some ideas above, but the fact remains that it's not easy to accurately measure the resistance of a mod without some pretty good equipment. the device he has access to can measure in the range of micro-ohms (that's one millionth of an ohm), which is definitely good enough, but then the problem becomes hooking it up correctly to take an accurate measurement.

the answer to your second question is yes. the voltage drop across everything (mod and atty) will always be the same as the voltage of your battery, meaning if your battery is at 4v, the voltage drop across the mod plus the voltage drop across the atty will add up to 4v. obviously, if more voltage goes to your mod, less goes to your atty, which is why mods with a low voltage drop are seen as better.

the way these drops are related is by the resistance. for the sake of simplicity, let's say the mod's resistance is 1 ohm and the atty's is 2 ohms. in this case, the atty will have twice the voltage drop of the mod. since we know that the battery is at 4v (and therefore the total voltage drop must add up to 4), we can calculate that 1.33v will go to the mod, and 2.67v to the atty.

if we keep the same mod and replace the 2 ohm atty with a 3 ohm atty, we now know that the atty will have 3x the voltage drop of the mod. in this case, 3v will go to the atty, and only 1v will go to the mod.

does this make sense? i try not to get too technical, but i work with electricity every day, so my perception of what's "too technical" may be a bit skewed...

also, your second question is brilliant. we don't have to directly measure the resistance of the mod if we can (VERY) accurately measure the difference between the total voltage drop vs the drop over the atty... jkuro's tests are good, but not quite accurate enough if he's getting 0.00v drops in some cases.

hmm, this gives me an idea, now if only i had some (very expensive) voltmeters...

yes. makes total sense. Your examples are illustrative of the flow of energy of batt output. i learned something today.

Learning the DC (?) or resistance of the mod would clarify, verify the "this mod hits like a freight train" type of spec and separate the mech from the atomizer... but a question; doesn't the atomizer body contribute to v loss as well? or does the coil resistance alone represent the total atomizer resistance?

 

[vapo jam]

yes. makes total sense. Your examples are illustrative of the flow of energy of batt output. i learned something today.

Learning the DC (?) or resistance of the mod would clarify, verify the "this mod hits like a freight train" type of spec and separate the mech from the atomizer... but a question; doesn't the atomizer body contribute to v loss as well? or does the coil resistance alone represent the total atomizer resistance?

good questions!

first, just to clarify, please disregard the DC in DC resistance; it means Direct Current (ie, the current flows in one direction) as opposed to AC resistance/impedance (Alternating Current, or the current switches directions). force of habit on my part, but it's exactly the same type of resistance we measure on our coils.

yes, learning the resistance of a mod would verify whether the mod "hits like a freight train" or not. i don't know real numbers, but let's say one mod has a resistance of .05 ohms, and another a resistance of .0001 ohms. in a direct comparison, the mod with a resistance of .0001 ohms would definitely hit like a freight train. the best part is that it would always be comparable to the resistance of any other mod, so you'd know right off the bat that a .0001 ohm mod hits harder than a .0025 ohm mod, which hits harder than a .05 ohm mod.

in comparison, jkuro's tests are comparable to each other, since he tests everything the same way. however, if i were to say i measured a voltage drop of .02v on a chi-you clone, using a 1.1 ohm atty and a battery charged to 4.1v, this number would have absolutely no meaning in relation to jkuro's testing (or anyone else's tests for that matter, unless they did the exact same thing that i did). if i were to do the exact same test later in the day when my battery only had 3.4v left, this test would have no meaning, even in relation to my previous test.

the atomizer body does indeed contribute to the resistance, however, most of us measure this anyways and group it with the coil. any resistance checker that has a 510 connection measures not just the coil, but everything between the center contact and the 510 threading of the atty. to get a true measure of just the coil, you'd have to use a meter with probes, and press the probes against the ends of the coil wire where they're held in by the screws. as with the mod, though, unless you have a really bad atty, it would likely take very sensitive test equipment to detect a difference between the resistance of just the coil vs the total atomizer resistance.

whew, i'm quite the nerd, aren't i oh well, time for dinner

 

[K_Tech]

As to the body of the mod, its resistance is directly related to the thickness of the body and the length of the tube.

As the thickness of the metal goes up, resistance goes down, and as length goes up, the resistance goes up. It works the same way with wire - thinner, longer wire is more resistant to electrical current flow than shorter, thicker wire.

Different materials have different electrical properties. In order of best to worst, this list looks like:

1. Silver
2. Copper
3. Gold
4. Aluminum
5. Titanium
6. Stainless steel

It's interesting to note (at least to a geek like me) that although stainless steel is the "worst" performer on the list, we're talking VERY low values of resistance. SS is ten times "worse" than silver at conducting electricity, we're still talking differences in the nano-ohm range.

The actual moving parts, transition joints, and contact surfaces, in my opinion, contribute more to a "good hitter" than the actual material it's made of (unless we're talking rubber vs. copper, lol).

 

[vapo jam]

since it's used so often in mods, i'll add one more material to k tech's list:

1. Silver
2. Copper
3. Gold
4. Aluminum
5. Brass
6. Titanium
7. Stainless steel

It's interesting to note (at least to a geek like me) that although stainless steel is the "worst" performer on the list, we're talking VERY low values of resistance. SS is ten times "worse" than silver at conducting electricity, we're still talking differences in the nano-ohm range.

brass mods are typically considered pretty hard hitters, yet brass is only 26.67% as conductive as silver.

The actual moving parts, transition joints, and contact surfaces, in my opinion, contribute more to a "good hitter" than the actual material it's made of (unless we're talking rubber vs. copper, lol).

agreed. this is why telescopes typically don't hit as hard as solid tubes. any point at which there's a 'break' in the material (especially threaded parts) contributes much more to the overall resistance than the material.

 

[TheBeardedMann]

Totally agree with all the above. But to add a bit more to this, even if you get to the point where you find the voltage drop and whatnot, I'd like to see an experienced vaper's opinion on when it makes a difference. Of course, it would be subjective to the vaper's opinion, but it would be very interesting to see someone post all these specs between mods and then have a "field" difference. I'm going to guess that the slight differences between mods (yes, some do have horrible drops and those will be noticeable) don't actually have an end user effect. But, just like overclocking a computer, I'll tweak what I got to get every 0.0001 volt I can.

 

[ukeman]

All very interesting, for an avid non tech, fanatic mech fan who wants the best conductivity (hits like a train) mod.
Its one of the criteria I have along with the functional design of the switch (conductive and easy).

thanks K tech and vapo jam!

I'm well assured that many an experienced mech user (especially around southern Calif. where there are lots of shops and vaper dudes) will and do corroborate these factors through actual hands on vaping. (I frequent the forum where jkuro's testing is posted),

But as we are in the intermediate phase of this industry its tricky assessing new products that come out and if it is spot on in desirable factors, its not easy to get one in the first runs.

 

[vapo jam]

Totally agree with all the above. But to add a bit more to this, even if you get to the point where you find the voltage drop and whatnot, I'd like to see an experienced vaper's opinion on when it makes a difference. Of course, it would be subjective to the vaper's opinion, but it would be very interesting to see someone post all these specs between mods and then have a "field" difference. I'm going to guess that the slight differences between mods (yes, some do have horrible drops and those will be noticeable) don't actually have an end user effect. But, just like overclocking a computer, I'll tweak what I got to get every 0.0001 volt I can.

in my completely non-scientific opinion, i would guesstimate a voltage drop of .05v or less would not be noticeable. i picked this number entirely because some people claim to be able to tell the difference between .1v adjustments on a provari, and some claim to not.

that being said, i'd take every extra .0001 volt i can get as well.

 

[vapo jam]

All very interesting, for an avid non tech, fanatic mech fan who wants the best conductivity (hits like a train) mod.

haha, to be completely honest, that's all i want as well. all of my ranting and raving is mostly due to the fact that we don't have a good way to easily compare this (although i will admit, jkuro's list seems more comprehensive every time i look at it...)

 

[WattWick]

Interesting topic for sure. Even for one who is not that concerned about it. For me, voltage drop is only an issue if it's noticeably bad. Still, those more into it than me provide very useful information in knowing what to expect before hitting that Buy button. Quantifying it in some way makes for way more useful info than the fact that you can blow "monster clouds" with basically anything given the right conditions. I don't care for monster clouds, but I do get annoyed if a brand new mod proves somewhat anemic and wasteful of my precious mAhs.

 

[edyle]

So how do you go about finding the DC resistance of the mod?
And is jkuro (and by a different route - us taking an atomizer and inline meter ie on a mod to measure the diff under load) a round about way of measuring the resistance of the mod?

You can actually guesstimate it from the voltage drop and knowing your coil resistance.

If the resistance of the mod (including battery) is equal to the coil resistance, the voltage drop will be 50%.
If the resistance of the mod (including battery) is 10 times the coil resistance, the voltage drop will be about 10%

 

[edyle]

in my completely non-scientific opinion, i would guesstimate a voltage drop of .05v or less would not be noticeable. i picked this number entirely because some people claim to be able to tell the difference between .1v adjustments on a provari, and some claim to not.

that being said, i'd take every extra .0001 volt i can get as well.

Voltage drop is like when you measure 4.2 volts on your mod,
then when you put on your dripper,
attach the voltmeter to the dripper to check voltage UNDER LOAD,
and you fire the mod and get a voltage of 3.7 volts,
then your voltage drop = 4.2 - 3.7 = 0.5 volts.

This kind of thing will happen with low ohm coils (or with faulty mods that have excessive contact resistance).


Voltage Drop:
It's like when you plug in something in your house and you see your lights dim.

 

[rucni]

as a relative noob to the higher tech of the vaping world and with a limited budget i bought a hammer clone from FT and i knew before i got it i was going to have voltage drop issues. now now having the tools to check my batteries and ohms with multi meter i settled for using my vamo. and i found with a 1.5ohm coil and freshly charged battery i was only able to vape until the battery hit 3.5 volts, as shown on my vamo. now the vamo will cease working at 3.2 volts, so i assumed i was getting a 0.3 voltage drop. since then i have replaced the center pin spring and if i am not careful i have vape until my battery goes below the 3.2 volts, when this happens i cannot turn the vamo on to check the battery. but i have learned that asm y battery looses charge from use the size of my cloud deceases.

 

[Dampmaskin]

You can measure low resistances with a voltmeter, a resistor with a known value, and a stable voltage source: Put a no-res dummy battery in the mod. Put the known resistor in series with the mod, and apply a voltage to the circuit. (Of course you have to select a known resistance value and voltage that yields a sane current/power, unless you want to fry something.)

Measure the voltage over the resistor, and the voltage over the mod. Then it should only be a matter of some simple calculations to get the resistance of the mod.

The biggest variable and source of error here I would guess to be the 510 connector you're using.

 

[edyle]

as a relative noob to the higher tech of the vaping world and with a limited budget i bought a hammer clone from FT and i knew before i got it i was going to have voltage drop issues. now now having the tools to check my batteries and ohms with multi meter i settled for using my vamo. and i found with a 1.5ohm coil and freshly charged battery i was only able to vape until the battery hit 3.5 volts, as shown on my vamo. now the vamo will cease working at 3.2 volts, so i assumed i was getting a 0.3 voltage drop. since then i have replaced the center pin spring and if i am not careful i have vape until my battery goes below the 3.2 volts, when this happens i cannot turn the vamo on to check the battery. but i have learned that asm y battery looses charge from use the size of my cloud deceases.

About 10% voltage drop with a 1.5 ohm coil, so that means you had about 0.15 ohms extra resistance on the mod (including battery);

yes that spring would be the reason; drop the old spring in some vinegar to soak and see if it turns all shiny.

 

[vapo jam]

You can measure low resistances with a voltmeter, a resistor with a known value, and a stable voltage source: Put a no-res dummy battery in the mod. Put the known resistor in series with the mod, and apply a voltage to the circuit. (Of course you have to select a known resistance value and voltage that yields a sane current/power, unless you want to fry something.)

Measure the voltage over the resistor, and the voltage over the mod. Then it should only be a matter of some simple calculations to get the resistance of the mod.

The biggest variable and source of error here I would guess to be the 510 connector you're using.

this is pretty much what i was thinking, except i thought it might be easier to get a known-resistance dummy battery, and attach the voltage source to a 510 adapter (or i suppose at this point you could just attach an ohmmeter to the 510 adapter instead). the trick would be getting the battery dummy, though; unless anyone knows something i don't, i imagine it would have to be custom made.

 

[Dampmaskin]

You can buy copper rods on fleabay. If you get a C10100 grade copper rod 14 or 15 mm in diameter, cut it to length with a hacksaw, and throw some insulating tubing on it, you have yourself a dummy flat top battery with no resistance to speak of. Or maybe a thinner rod with thicker insulation would be better? IDK.

If you have access to a lathe, making button top dummy batteries shouldn't be too hard either. Even a dremel would suffice. Copper is soft, and easy to grind down.

 

[vapo jam]

You can buy copper rods on fleabay. If you get a C10100 grade copper rod 14 or 15 mm in diameter, cut it to length with a hacksaw, and throw some insulating tubing on it, you have yourself a dummy flat top battery with no resistance to speak of. Or maybe a thinner rod with thicker insulation would be better? IDK.

If you have access to a lathe, making button top dummy batteries shouldn't be too hard either. Even a dremel would suffice. Copper is soft, and easy to grind down.

hmmm, i wouldn't go so far to say they're cheap, but copper rods do seem less expensive than i thought they'd be... perhaps some Ø5/8" rods with shrink tubing on the outside would make good dummy batteries.

i'm not too concerned with flat-top vs button-top. my goal is to short the contacts together in order to read the resistance of the mod, i figure this would best be achieved by sanding down the ends to get nice, smooth connection surfaces.

 

[edyle]

hmmm, i wouldn't go so far to say they're cheap, but copper rods do seem less expensive than i thought they'd be... perhaps some Ø5/8" rods with shrink tubing on the outside would make good dummy batteries.

i'm not too concerned with flat-top vs button-top. my goal is to short the contacts together in order to read the resistance of the mod, i figure this would best be achieved by sanding down the ends to get nice, smooth connection surfaces.

a long 1/4" bolt, and two rubber washers; you can make the rubber washers using silicone;

the washers hold the bolt off the sides of the tubing; the washers dont need to be anywhere near exact, they can even be square; they just have to fit;

the bolt you cut to 65mm to simulate the 18650 battery lenth; make it 66mm or 67mm just to be sure; 64mm might be too short. The bottom spring would take care of an extra milimeter or two.

 

[vapo jam]

a long 1/4" bolt, and two rubber washers; you can make the rubber washers using silicone;

the washers hold the bolt off the sides of the tubing; the washers dont need to be anywhere near exact, they can even be square; they just have to fit;

the bolt you cut to 65mm to simulate the 18650 battery lenth; make it 66mm or 67mm just to be sure; 64mm might be too short. The bottom spring would take care of an extra milimeter or two.

that's an even better idea - looks like a set of copper bolts is much cheaper than a copper rod, and i doubt the results would be significantly affected.

 

[Dampmaskin]

I found this page, looks like a nice walkthrough:
How to Measure Low Resistances - Robot Room