Is this battery and the math safe?

[qfivenine]

I am waiting for my first mechanical to arrive, including some Sony Konion US18650VTC4 2100 mAh. I also have AW lMR 18650's. I calculated the minimum resistance that I could use with either with the formula R = E / I.So, let's do this:AW lMR 18650 (assuming 10 amperage limit):R = 4.2 / 10 = 0.42 ohmsSony Konion US18650VTC4 2100 mAh (30 amperage limit):4.2 / 30 = 0.14 ohmsIs this correct? I don't really plan on going below 0.9 so this is just for sake of knowledge. I understand that this formula assumes that you drive your battery to its limits the whole time which is probably a bad idea.What is the lowest you could go with the AW lMR and the Sony VTC4? Thanks!

 

[indoorsindica]

Correct .14 would be pushing the limit of those.

Ohms law... there's an app for that!

 

[State O' Flux]

Here is a, somewhat conservative, minimum resistance chart by Steam Turbine, based on some research Baditude had done previously.

 

[qfivenine]

Thanks! And sorry for the weird formatting on my post (at least it hasn't any whitespace on my side, I did put them in when writing the post though).

 

[Enoch777]

The math seems correct plugged into Ohm's Law Calculator.

Two things though:

let's do this:AW lMR 18650 (assuming 10 amperage limit)

Never assume the continuous amperage of your battery, or the resistance of your coil. Always check. Always.

Second, I don't think anyone sane would build a .1 or .2ish resistance coil. You never know what heating & cooling (shrinking and expanding) as well as various other factors can do to your coil. If it drops by .1 ohm you're spiking from 20 to 41 amps (assuming it's a .2 ohm coil) Not safe.

I won't speak to pushing the limits with relative safety, I tend to err on the side of caution. Even if I had the VTC4s, which I do plan on getting, I'm not sure I'd go below .4 ohms and likely would sit mostly between .5 and .7.

To answer your question, I'd say .3 ohm for the VTC4s and .6 ohm for the IMRs. That's roughly 60 and 30 watts respectively. Plenty of power, but that does seem to be pushing the limits while still being as safe as you can.

 

[indoorsindica]

Lowest you can go with an aw depends on which one you are using 18650, 18490, 18350 (s)?

 

[JmanEspresso]

If you're using the:

AW IMR 18650 1600mah version, its a 24amp limit. .18ohms is the lowest
AW IMR 18650 2000mah version, its a 10amp limit .42ohms is the lowest
AW IMR 18490, its a 15amp limit .28ohms is the lowest
AW IMR 18350, its a 6 amp limit .7ohms is the lowest


My personal rule of thumb is as follows:

18350- no lower than .8ohm
18490- no lower than .5ohm
18650 2000mah- no lower than .5ohm
18650 1600mah- no lower than .2ohm

There is a reason that the only one Im comfortable pushing to its limit is the 18650 1600mah version, and that is because it is a solid gosh darn battery. However, .2ohm is LOW, and you need to seriously consider what you're doing. When the resistance is that low, I personally suggest using a really low gauge wire so you can get a couple wraps to the coil. If you're doing a .2ohm coil and there is only like 1-2wraps, you are literally millimeters away from a short. If you've got like 5-6 wraps, you've got a little more leeway.




Start at 1ohm and work down slowly. And if its clouds you are after, I have one word... AIRFLOW. Airflow does way more for cloud plumage than low resistance does. With the right airflow, you can change the humidity of a room on a .7ohm build.

 

[dylanlg2]

jman is right .. sony makes another vtc I believe with much lower mah. these are better for sub ohm than the higher mah ones you have.... I would build everything in the mentality that you simply have 1600mah mnkes.. just to be safe... I stick around .4 with my mnke and getting the low mah vtcs soon,

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