I've ran the math on my triple 18650 parallel box and it seems my amperage limit is about 45A combined (thats with 5amps removed from each battery) so I'm just wondering how low I can build before I'm being risky... I mostly build at .2 ohms, but the low resistance wire I just got takes an insane ammount of wraps to get there. I havnt been able to find any info on this, and was hoping someone could help me out with this... I'd like to know I'm not going to vent my batteries if I try this wire framed... Cancel that my lowest ohms should be 0.098 (with recalculated amps) (still feels risky for some reason to me)
Checking this out for safety is the right thing to do
You have three batteries in parallel in a mechanical mod. With freshly charged batts the circuit is 4.2V. The amp draw is
easily calculated from ohm's law using 4.2V and the resistance of the build. That amp draw is split between the batteries.
That means if you're using one 20 amp battery 0.21 ohms draws 20A so that's the low resistance limit. With two batteries in parallel (40A limit combined) it's around 0.11 ohms. With three batts (60A combined) it's around 0.07 ohms.
There are a couple of other things to consider though, as with most things.
For safety, think about how accurately you can measure the resistance. If your meter is high by only say 0.05 ohms (which is entirely possible), a 0.02 ohm build would show as 0.07 ohms but actually be 0.02 which would draw 70A from each battery. That's way over the max continuous amp draw the battery is rated for and well into the danger zone. The same 0.05 ohm error with a 0.21 ohm build (single 20A battery) = 0.16 ohms, which draws 26A. A bit high, but not nearly as bad as 70A.
In the same vein, if you have a sightly loose wire connection the resistance will read a bit high but that could go down if the connection changes. Again, the lower you build the more significant that would be for the batteries.
Then there is the power thing. In a mech mod with a single or multiple parallel batteries, build resistance is the biggest factor that determines the power (watts) output. With mutiple mech mod batteries in series it all changes because circuit voltage goes up.
So at 0.21 ohms you're making around 70 watts considering a bit of voltage drop, at 0.11 ohms it will be around 130 watts and at 0.07 ohms it will be around 200 watts. These three vapes will be completely different and you'll probably want to set the builds up very differently for each.
When I design a build for a mech mod I start the process with the power I want. That determines the wire gauge I need to get the number of coil wraps with the number of coils I'll be using to get the vape I want from it.
Unfortunately you're working with a given low resistance wire. Stuck with that as a starting point, I would think about the number of coils, the number of wraps and the inside diameter used to get the resistance (and power) I want. Taking one coil out of a dual coil build gives you twice the resistance and half the watts. Using more wraps, as you know, increases the resistance of a coil at the expense of more heat up time when you push the button. Building on a bigger pin reduces the number of wraps needed to get the resistance you're after.
I wouldn't go lower ohms in a mech mod than I had confidence in the calibration of my meter and my skills to make sure I was going to be safe. I also wouldn't go so low that the vape was going to be too aggressive.
0.1 ohms is too low for me for safety. I also wouldn't like the vape, but that has nothing to do with the battery safety aspect. IMO if you can't get a build with the wire you have at high enough resistance to be comfortable for you, don't do it. You can get a 30 foot roll of wire for under $10.
