Puzzled- Dual Coils half's the Ohms- Why?

[niczgreat]

I just built a Dual Coil Recomizer 2.

I built the first coil and it tested at .23 Ohms
so then I built a second more or less identical coils.
The ending dual coil setup measured in at .13 ohms.

So I'm puzzled, logic is that if you are building 2 coils that you double the length of wire
so the build should come out with double the resistance or been in the .4 ohm range.

But in the real world making Dual coils just about Half's the Resistance [ Ohms]

Why?

 

[Woody_]

Because they are wired parallel. If you want .23 ohms dual coil, you need to make two .46 ohm

 

[Miata GT]

The resistance is decreased because you are providing 2 paths for the electricity to travel.

 

[Nermal]

Good on ya, Tom for using that ohm meter!

Let's use the water analogy, with water being analogous to current flow. We have a one inch pipe carrying a given volume of water. Now, we place an identical pipe beside it - same size, same pressure. Suddenly, we are flowing twice the water because we have half the resistance.

Now, if we put those two pipes end to end, we would double the resistance, and halved the flow exactly as you expected.

If I haven't made it clear, I bet someone else can do better. Stick with that meter, and maybe discuss with someone whether that is a good resistance for your battery. We're at the point that I'm getting over my head, but that sounds like an awfully low resistance.

 

[niczgreat]

Hi Nermal
Good analogy
Sony Vtc5 Bats at 30 amps can handle it.

 

[Baditude]

• Sony Vtc5 30 amp continuous discharge rate.
• 4.2 volts (fully charged battery).
• 0.13 ohm total resistance coil.

current draw via Ohm's Law Calculator = 33.3 amps


You are over the recommended amp limit for that battery.

At 0.13 ohms you are putting a lot of faith in whatever meter you are using to be precisely accurate up to a tenth of an ohm.

You are just 0.13 ohm away from a dead short. A dead short will push any battery (even a 30 amp battery) into thermal runaway.


Ohm's Law for Dummies

 

[niczgreat]

• Sony Vtc5 30 amp continuous discharge rate.
• 4.2 volts (fully charged battery).
• 0.13 ohm total resistance coil.

current draw via Ohm's Law Calculator = 33.3 amps


You are over the recommended amp limit for that battery.

At 0.13 ohms you are putting a lot of faith in whatever meter you are using to be precisely accurate up to a tenth of an ohm.

You are just 0.13 ohm away from a dead short. A dead short will push any battery (even a 30 amp battery) into thermal runaway.


Ohm's Law for Dummies

Continuous 30 Amp- burst rate higher approx 60Amp
I don't hold button more than 2-3 seconds- Continuous is 6-7

In addition battery is not getting hot.

I'll risk it.

 

[brickfollett]

Continuous 30 Amp- burst rate higher approx 60Amp
I don't hold button more than 2-3 seconds- Continuous is 6-7

In addition battery is not getting hot.

I'll risk it.

Good luck lol, thats a dangerous game your playing.

That said, I about lost it at my local vape shop when these kids were telling be about their .07 ohm coils with VTC 5 batteries, on a mod with no venting. Dudes were vaping on a pipe bomb...

Baditude can more than comment on his battery experiences. I'm not comfortable going anywhere below .3 ohms, and haven't tried yet. Lowest I've gone is .43, and my current build is .49 on my Reo. All with VTC 5 batteries

Stay safe

 

[Nermal]

Glad a few people with more knowledge than eGo twist using me.

 

[Maestro]

Imagine you're blowing through a straw. Then pinch it in the middle. It's harder to blow through. That's resistance. Take a second straw and pinch it the same way and stick it into the end of the first straw. Now it's twice as hard to blow through. That's because it's connected in series. Take the second straw out and put it in your mouth (still pinched) next to the first straw. Now it's easier than the first straw by itself. That's because it's in parallel, not series. In fact it you put 20 straws pinched like this in your mouth you would barely feel any resistance at all. They're all in parallel. Connect all 20 straws end to end so it's in series and you likely wouldn't be able to blow through it at all.

That's why 2 coils arrange in parallel have less resistance than 1.

 

[Baditude]

Continuous 30 Amp- burst rate higher approx 60Amp
I don't hold button more than 2-3 seconds- Continuous is 6-7

In addition battery is not getting hot.

I'll risk it.

It's your face and hand, not mine. Having had a battery explode in a mechanical mod before, I know better than to push a battery unnecessarily. That's not something that I wish to experience again in this lifetime.

The current standard of rating amps for batteries is to use continuous discharge rate, not burst discharge.

 

[CloudZ]

The current standard of rating amps for batteries is to use continuous discharge rate, not burst discharge.

Yep... and it is not hard to imagine an accidental continuous discharge event. Even if it doesn't melt their face off, it could still burn their house down.

 

[jersey_emt]

It's your face and hand, not mine. Having had a battery explode in a mechanical mod before, I know better than to push a battery unnecessarily. That's not something that I wish to experience again in this lifetime.

The current standard of rating amps for batteries is to use continuous discharge rate, not burst discharge.

A lot of people (myself included) like to use 50% of a battery's maximum continuous discharge rate. This means 15 amps for a Sony VTC3/4/5, allowing you to go down to 0.28 ohms, which is plenty low. I've tried coils up to the full 30 amps on my VTC4 and VTC5's (0.14 ohms) and there was not any increase in vapor compared to the similarly constructed (same gauge wire and same coil diameter, just more wraps) 0.28 ohm coils. Actually, if anything the 0.28 ohm coils performed slightly better owing to the increased contact area between wire and wick.