Lowest ohms I can safely use?

[Dana A]

My friend is coming over shortly to have me rebuild her AGA T2. She is using a mech and wants it built lower then it is now which I think is like 1.5 ohms. She uses AW 18650s. How low can I safely go with these batteries. I don't use mechs and she is new to them. She wants me to do it in like 20 min but I want to be safe. I have 30 gage as well as 32 kanthal on hand.. Any suggestions?

 

[BillyWJ]

I'm new to RBAs and mechs, but I think there being a Kick involved there will be a big factor in how low you can safely go.

 

[Traver]

Considering your questions the answer is, don't.
First learn something about batteries. There are different kinds of Aw batteries with different discharge rates.
Do you have an multimeter to check for the ohms and shorts?

Here's an ohms calculator to give an idea of what you can do.
ohmslawcalculator.com/ohms_law_calculator.php.webloc

 

[Thrasher]

for a mechanical i usually stick to .8-1.0 ohm range for best battery life VS performance. in my opinion 1.5 will work but is a little high for a mechanical to work well once the battery drops into the 3.7 and lower range.

the aw 2000 is 10 amps
the AW 1600 is well over 15 amps
so staying around .8 or higher is plenty fine. with minimal experience anything lower then the that will be problematic as the coil heats up fast! and can hot spot like crazy,

 

[DaveP]

Check out the current ratings for batteries. The "C" number is the maximum current draw it can provide. If your battery is rated at 2000mah then it can run at that load for one hour. If that battery is rated at 10C, it can safely provide 10 x 2000ma, but not for long. If you load it at that rate, it might just last 6 minutes. Check out the ohms law calculators to see how many amps your particular coil will draw.

1.5 ohms at 3.7v will draw 2.46 amps. A .8 coil will draw 4.6 amps. Her batteries will last a little over half the time on a .8 coil. My AW 18650 batts will supply 2000mah for an hour. 2000mah = 2 amps. If I pull 4.6 amps I could get less than a half hour of operation, for example. If I pull 2.46 amps my battery would run for a little under an hour.

Check it out here ...
http://www.ohmslawcalculator.com/ohms_law_calculator.php


Some info on different battery ratings. Look at the chart labeled "Discharge time in hours".
Battery test-review 18650 summary

The candlepower forum guys are the gurus on this subject. They have been doing this much longer than ecigs have been around. Yes, they sometimes have a flashlight spew on them.

Maximum current on non protected 18650's

 

[bones1274]

The AW IMR 18650 2000 mah batteries are 10 amp. The AW IMR 18650 1600 mah batteries are 24 amp.

I have a mech mod with a RBA and I use a 0.8 ohm micro coil and my 1600mah AW 18650 lasts a day and a half and about 10 ml of juice. My mech mod will safely go down to 0.6 ohms before you have to worry about voltage drop or collapsing the hot spring.

Use the ohms law calculator posted above and do research on the mech mod you will be using to find out what the safe limits of the mod are. You will also need an ohm meter to accurately know what your coil measures out as. Once you get the hang of wrapping coils, it will not take you long. I can wrap a micro coil and wick my RBA in less than five minutes.

Last, but not least, use the link below to get an approximation of how many wraps for your wire gauge it takes to get to your desired coil ohms. An ohm meter is still a must though.

http://www.e-cigarette-forum.com/forum/reos-mods/446263-micro-coils-ohms-description.html

 

[crxess]

Would not do ANYTHING for someone else I have not done for myself. Just my way of protecting others.

 

[DaveP]

The AW IMR 18650 2000 mah batteries are 10 amp. The AW IMR 18650 1600 mah batteries are 24 amp.

I have a mech mod with a RBA and I use a 0.8 ohm micro coil and my 1600mah AW 18650 lasts a day and a half and about 10 ml of juice. My mech mod will safely go down to 0.6 ohms before you have to worry about voltage drop or collapsing the hot spring.

Use the ohms law calculator posted above and do research on the mech mod you will be using to find out what the safe limits of the mod are. You will also need an ohm meter to accurately know what your coil measures out as. Once you get the hang of wrapping coils, it will not take you long. I can wrap a micro coil and wick my RBA in less than five minutes.

Last, but not least, use the link below to get an approximation of how many wraps for your wire gauge it takes to get to your desired coil ohms. An ohm meter is still a must though.

http://www.e-cigarette-forum.com/forum/reos-mods/446263-micro-coils-ohms-description.html

My quotes for time in the previous post were theoretical for continuous firing at the given coil resistance. Yes, you could get an all day vape at .8 ohms for a cumulative fire time that totaled about 30 minutes. We vape in increments of a few seconds at a time.

http://www.kritikalmass.net/battery-calculator/index.php

Chart of C ratings vs size

These ratings are general guidelines taken from information on the internet and NOT all from the manufacturers.

1C or less for some Li-FePo4
Assume 1C for generic Li-ion unless otherwise noted
1.5C for ultra/sure/trust/-fire Li-ion
2C for AW ICR (Li-ion)
3C for BDL 10440 IMR (Li-Mn)
5C for BDL 14500 IMR (Li-Mn)
8C for AW 14500 and 16340 IMR (Li-Mn)
10C for AW 18650 IMR (1600mAh) (Li-Mn)
10C for AW Li-FePo4

Max drain rate in amps is C in mAh / 1000 x C rating

Example: an AW IMR Li-Mn 14500 battery has a capacity of 600mAh. The C rating is 8C (it can supply a load of 8 times the capacity).
Therefore the max discharge current in amps is: 600 x 8 over 1000 (600 multiplied by 8 divided by 1000)
= 4800 / 1000
= 4.8 amps

This shows it has enough beef to safely and effectively run an atomizer - which some 14500's don't. In other words it is less likely to go into thermal runaway if there is an internal fault in the battery, is overcharged, and is then used to power a device that draws a relatively high current such as an atomizer; and it will not suffer from excessive voltage drop when powering the atty.
Useful formulas

 

[UnclePsyko]

I agree with the above posters... If you have to ask just to double-check, that's one thing, but if you never did such a build without knowledge of the battery/device/coil, and without a multi-meter and know how to use it, you're not ready yet!
Some research and tutoring on your part is necessary for safety's sake. These batteries we use are no joke!
You don't want to end up on the local news for injuring your friend, and the news outlets savor these stories!

 

[cantstopwontstop]

Personally you would probably be OK around 1 ohm. This is what i run all my Genesis atomizers at. Anything lower than .8 and i have trouble with the wicking/heating ratio. With the batteries you mentioned a 1 ohm coil is going to draw 3.5-4.5 amps from your battery, which is a relatively safe range. Do you have a meter?

And everyone who posted already is right, knowing your batteries is key with a mech mod. They become you "weakest link" when you have no built in short protection, thus are the most likely and worst thing that could potentially fail in your friends set up. Knowledge is key in this situation and all vaping practices, esp. rebuilding.

 

[Bosco]

If she's at 1.5 now try going to 1.2 or so. That should make a noticable difference in the vape quality. I think to get 1.2 you're looking at the 30 more than the 32 gage . .at least I would be . .something like 5/6 wraps, depending on id of coil, of course.

At 1.2 ohms you have should have nothing to worry about, battery-wise .. I am assuming she's got the AW IMR . .if not then research cause I have no idea except about the other AW batts out there. You likely *could* go to .6 or even lower but I find with builds like that the whole device has to be set up special - ie - huge airflow, really good wick, etc . .and then it's a really intense vape she may not enjoy. I'd say if she wants it lower than around 1.0 she should learn to do it herself because coils like that don't even last all that long, in my experience.

 

[tj99959]

The thing is 'not all coils are created equal'. Here's you an example: I have two identical RDA's sitting in front of me. One has a 5/6 wrap of 30ga in it (1ohm+/-), the other has a 9/10 wrap of 30ga in it (2ohm+/-). If you were to say that the 1ohm coil vaped hotter than the 2ohm coil you would be wrong. The 1ohm coil is a conventional coil, and the 2ohm coil is a micro.

 

[Dusif]

My friend is coming over shortly to have me rebuild her AGA T2. She is using a mech and wants it built lower then it is now which I think is like 1.5 ohms. She uses AW 18650s. How low can I safely go with these batteries. I don't use mechs and she is new to them. She wants me to do it in like 20 min but I want to be safe. I have 30 gage as well as 32 kanthal on hand.. Any suggestions?

I wouldnt go lower than 1 ohm... But on a genny 1.5 is really good... Just make sure the wicking is awesome and lower ohm wont be needed... Buy you could dual coil it with 2x 2 ohm coils?


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[Myrany]

Frankly I wouldn't ever do a genny setup for someone else. Gennys can become fiddly and finicky and change behavior on a dime. The person using it needs to be able to handle adjusting it as needed when it misbehaves.

I would teach someone how to build it and all the relevant safety information about batterys and shorts and then let them build their own setup.

I personally think handing someone that knows nothing about it a built Genny is a somewhat unsafe idea.

 

[goodoleboy45]

I use 1.1 to 1.4 ohms in my mechs but I run 18500 battreys. 0.8 to 1.1 is safe for 18650 depending the C rating

 

[sinistergentlemen]

There is a really great video on YouTube from cloud chasers about building sub ohms and the safety tips about batteries and what not to do.


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