0.6 voltage drop. Can someone explain?

[illitirit]

I would like to know why my brass nemesis + origen v2 dripper have such a high voltage loss @ 0.3 ohm dual coil setup.

If I build a single coil 0.8 ohm my voltage drop is around 0.18.

Im sure the explanation is simple, but why is it that the lower ohm your coil is, the more voltage loss you get?

And 0.6 drop @ 0.3 ohms dual coil. I dont know if this is normal or not, considering i get really low voltage drop at higher ohms.


My batteries are sony vtc5 . All my voltage drop tests were on a fresh battery. Thank you for any help.

 

[MorpheusPA]

It's sometimes easier if you think of the battery as a tank and hose. What happens if you run a hose full-open? The pressure in the line drops. If no water is running, the pressure is as high as it can get (the same in the tank, optimally, but the analogy fails pretty badly here).

Low ohm coils open the hose much more fully than high ohm ones do--more power (more water) is flowing through the low ohm coil.

The hose just can't keep up, so pressure drops. When you stop pulling power, the pressure recovers.

That's not accurate, it's just a handy way of thinking about it. When you have time, look up "internal resistance" on a battery.

 

[illitirit]

So essentially, im maxing the capabilities of my battery rather than my mechanical mod?

I understand that all batteries have internal resistance. I was thinking maybe its simply the conductivity of brass. Im sure if I fired the same coil i tested on any of my stainless steel mods, I would be getting probably 0.8-1.0 drop. I do own a copper mod but have not had a chance to do voltage testing with it, as I left it at a friends house in another state lol.

 

[MorpheusPA]

So essentially, im maxing the capabilities of my battery rather than my mechanical mod?

At least you're drawing it enough that the voltage drop is showing. I don't pretend to be an expert on your particular battery, but 0.6 V drop at 0.3 Ω sounds extremely reasonable to me.

Assuming a base voltage of 4.2 (full), you're tapping 14 A at 0.3 Ω. That's a lot of amps, even with a listed maximum of 30. It's no big surprise the voltage sags.

I understand that all batteries have internal resistance. I was thinking maybe its simply the conductivity of brass. Im sure if I fired the same coil i tested on any of my stainless steel mods, I would be getting probably 0.8-1.0 drop.

Go ahead and try. While the resistance of brass is greater than that of copper, and steel is also quite high, there's a lot of mass in the mod for electrons to move through. I'd imagine the contact points cause more resistance overall than the mod itself, and even then not very much. It's the combination of high resistance and tight pathway that creates and overall high resistance.

Even Kanthal wire isn't that resistant when used in large gauge--27 gauge Kanthal is only about 15 ohms per meter, or around 5 per foot. The pathway in your mod is far larger than a single 27 gauge wire, and not made of Kanthal.

I do own a copper mod but have not had a chance to do voltage testing with it, as I left it at a friends house in another state lol.

Again, try. Most of the "resistance" in a mod is actually voltage drop from draw. Most of the (very small) remainder is at the contacts.

Keep in mind that multiple samples are necessary as well. Most of us don't own a Fluke (I sure don't), and measurement can be somewhat...questionable...with cheaper meters.

I make electronics for fun, and always use pure copper wire (silver would be lower resistance, but it's pretty marginal in the gauges and lengths I use, not to mention expensive). I'm used to seeing voltage drop under power, and know it's not caused by the resistance in the system--I'm measuring directly off the battery itself in the housing.

One word of warning: 0.3 ohms is marginally dangerous if not using an extremely good meter (like a Fluke) that's been calibrated to validate it. With my meter, that's falling into the error band where I couldn't be completely certain it's not shorted as my meter simply won't read accurately less than 0.3. Please be careful out there.

 

[illitirit]

At least you're drawing it enough that the voltage drop is showing. I don't pretend to be an expert on your particular battery, but 0.6 V drop at 0.3 Ω sounds extremely reasonable to me.

Assuming a base voltage of 4.2 (full), you're tapping 14 A at 0.3 Ω. That's a lot of amps, even with a listed maximum of 30. It's no big surprise the voltage sags.



Go ahead and try. While the resistance of brass is greater than that of copper, and steel is also quite high, there's a lot of mass in the mod for electrons to move through. I'd imagine the contact points cause more resistance overall than the mod itself, and even then not very much. It's the combination of high resistance and tight pathway that creates and overall high resistance.

Even Kanthal wire isn't that resistant when used in large gauge--27 gauge Kanthal is only about 15 ohms per meter, or around 5 per foot. The pathway in your mod is far larger than a single 27 gauge wire, and not made of Kanthal.



Again, try. Most of the "resistance" in a mod is actually voltage drop from draw. Most of the (very small) remainder is at the contacts.

Keep in mind that multiple samples are necessary as well. Most of us don't own a Fluke (I sure don't), and measurement can be somewhat...questionable...with cheaper meters.

I make electronics for fun, and always use pure copper wire (silver would be lower resistance, but it's pretty marginal in the gauges and lengths I use, not to mention expensive). I'm used to seeing voltage drop under power, and know it's not caused by the resistance in the system--I'm measuring directly off the battery itself in the housing.

One word of warning: 0.3 ohms is marginally dangerous if not using an extremely good meter (like a Fluke) that's been calibrated to validate it. With my meter, that's falling into the error band where I couldn't be completely certain it's not shorted as my meter simply won't read accurately less than 0.3. Please be careful out there.

Thanks for you insight man, your very helpful.

the multimeter im using is about 10+ years old. It was my fathers. He gave it to me and told me that the thing was pretty expensive and extremely accurate. Considering he is an electrical engineer im going to trust him on this one lol. The multimeter has its own resistance, which i touch the probes together before measuring which is always 0.01. I then subtract that from my ohm reading on my coil.


Your point about thicker kanthal also didnt even cross my mind. Im using 24 gauge wire right now. I am sure that has to have some effect.

Is there a way to test voltage drop of just the mod itself? Like, without the atomizer screwed into the 510 connection. Is there a way to test the voltage drop of the battery tube itself?

 

[steved5600]

The way to test the voltage drop on the tube is to test the battery voltage then put it in the mech and test the voltage at the 510 connector. That will give you the voltage drop of the mech. Voltage drop is the voltage drop or across a part. If you know the voltage drop and the current/amps you can calculate the resistance of the mech.

 

[steved5600]

Oh Contacts are also a big factor. Copper contacts are the best followed closely by silver plated copper then brass etc.

 

[illitirit]

Oh Contacts are also a big factor. Copper contacts are the best followed closely by silver plated copper then brass etc.

True, im sure contacts play a huge part.

Im curious though. I have silver plated brass contacts right now. Do you think if i sanded and polished them it would improve conductivity?

 

[K_Tech]

True, im sure contacts play a huge part.

Im curious though. I have silver plated brass contacts right now. Do you think if i sanded and polished them it would improve conductivity?

Probably not, for a few reasons.

As long as the silver plating is properly bonded to the base metal, you're going to get better conductivity with the silver plate than with bare polished brass.

Also, the silver will stay conductive when it tarnishes.