# Safe sub ohming?



## bjorncoetsee

Hi I have a AW 2000mah 10A battery, I heard its not safe going below 0.8 with this battery with such low Amps, but I took a chance and I vape on a 0.5 dual coils now for a week and a half. Battery doesnt get hot and still have both hands.
But I bet it wont be safe going any lower?
Also is there a difference between vaping on a 0.5 single coils vs 0.5 dual coil on the same battery?

If I get the efest 3100mah 20A battery, will I be able to go 0.3 ohm?


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## Andre

I do find it surprising, to say the least, that you ask for advice whilst ignoring the safety precautions on the AWs. Why should one go to that trouble if you are not going to heed same? That said, it has been established that the 3100s actually have a continuous discharge rating of not more than 10 A, maybe even less. So the same safety limit applies as for the AWs. Suggest you get the Efest 2500s.

Reactions: Like 1 | Agree 9


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## Yiannaki

Andre said:


> I do find it surprising, to say the least, that you ask for advice whilst ignoring the safety precautions on the AWs. Why should one go to that trouble if you are not going to heed same? That said, it has been established that the 3100s actually have a continuous discharge rating of not more than 10 A, maybe even less. So the same safety limit applies as for the AWs. Suggest you get the Efest 2500s.


I agree with what @Andre has said here.
Also with mech mods you are venturing into the diy side of vaping.

Before even vaping at these low resistances or doing anything I suggest doing some research on this topic of safety as well as ohms law.

Reactions: Agree 1


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## n0ugh7_zw

bjorncoetsee said:


> Hi I have a AW 2000mah 10A battery, I heard its not safe going below 0.8 with this battery with such low Amps, but I took a chance and I vape on a 0.5 dual coils now for a week and a half. Battery doesnt get hot and still have both hands.
> But I bet it wont be safe going any lower?
> Also is there a difference between vaping on a 0.5 single coils vs 0.5 dual coil on the same battery?
> 
> If I get the efest 3100mah 20A battery, will I be able to go 0.3 ohm?


 
I'm new to this too.

I'm not trying to pick a fight, nor am I trying to humiliate you. But theres some stuff I need to say.

With this, or any other activity, your safety is ultimately up to you. What if you ask a question like that on the forums, and someone tells you to go for it and try a 0.15 ohm build on those batteries? 

NO!, you need to go and do some reading on battery safety, even better watch a couple youtube videos on it. Then you'll have a solid base of information, with which to gauge your safety. 

All that said, the only batteries that I think are worth trying sub-ohm builds with are :

Sony's (VTC3's, VTC4's or VTC5's)
eFests (purple 2500MAH) 

Thats it... there are other batteries, which will give you more battery life, but they have lower amp limits, and are therefore more suited to being used in regulated mods. (Regulated mods are generally suited to higher ohm builds)

Further more, you should really read up on ohms law, there are some great sites out there that will calculate how much your coils will draw from your batteries. 

The way you're doing this now, is like playing Russian roulette. Read up, and research this stuff. Go to as many sources as you can. Don't take any one person opinion for it. 

Because don't forget, if you blow a battery, its not just you that it hurts, it hurts the whole community, because it makes us all look like dodgy tinkerers who don't take precautions and who are a liability to have out in public places. It gives everyone who wants to stop vaping, ammunition to use against us. 

Like I said, I mean you no harm, but I have the feeling you need to be shocked into action a bit.

Reactions: Agree 5 | Thanks 1


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## Gazzacpt

There was a mech safety thread on this forum that was stickied if I remember correctly. 
You don't even have to look far all the info you need to help you and to be safe is around here if you browse a bit.

Reactions: Like 1 | Agree 2


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## JakesSA

Insofar research is concerned, the best site I've found is here. He tests batteries with a view to use in flash lights so his concern is more with continuous discharge. In reality this doesn't accurately reflect vaping battery usage but rather something like a 'jammed fire button' condition on a mech. 

The linked page allows you to compare different batteries at different current draws. Under the drop down is also a link that will take you to the full review of the battery.

As an example here is the discharge curve of the 3100 Efest vs the AWR, these were taken from the detailed test pages.
Note that the discharge is continuous and measured over a set amount of time at different currents (the colours) with two batteries, A and B as listed in the legend. Two batteries are tested to ensure the test gives consistent results. The test stops when the battery voltage (under load) reaches 2.8V, the minimum safe value.




What you can deduce from these charts, for example, is that:

At 10A the 3100 Efest will fire continuously for 10 minutes at which time the battery voltage (under load) will reach 3.2 volts.
At 10A the AWR will reach 3.2 volts (under load) in what looks like about 6 minutes, again under a continuous fire condition.

Lastly, what does this mean in Ohms? Well Ohms law says that 4.2V and a 0.42 Ohm coil produces 10A . Note I use the highest possible battery voltage for the calculation.

Reactions: Like 3 | Agree 2 | Winner 1


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## Alex

I run 0.5 ohm coils all the time in my Reo mini with both 18500 and 18490 efests, no problems at all.

Reactions: Like 1


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## n0ugh7_zw

@Alex, fair enough, but thats a bit of a dicey prospect for a noob, no? Also 0.5 ohms @ 4.2v (max one of those batts will put out when they're fresh off the charger) is 8.4A...

This guy is running 0.5 ohm dual coils... so actually a 0.25 ohm setup... thats 16.8A draw on a battery with a 10 amp limit... You see what I'm getting at, by being hard on him? its really not safe, what he's doing. not at all.

Also.. and i could be wrong here, but I don't think its outside the realms of possibility that he's going to discharge the batteries too far, that plus the massive drain on them is a time bomb as far as I'm concerned.


This site does all the math for you. http://www.steam-engine.org/batt.asp


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## JakesSA

@bjorncoetsee just for clarification is that 0.5 Ohm measured on the completed build or 0.5 Ohm per coil?

BTW, 0.5 Ohm current draw on the battery is the same whether its a single coil or dual 1 Ohm coils. 

Insofar the vape is concerned, its half the heat at each coil but double the surface area on a dual coil build .. me thinks..

Reactions: Agree 1


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## Alex

n0ugh7_zw said:


> @Alex, fair enough, but thats a bit of a dicey prospect for a noob, no? Also 0.5 ohms @ 4.2v (max one of those batts will put out when they're fresh off the charger) is 8.4A...
> 
> This guy is running 0.5 ohm dual coils... so actually a 0.25 ohm setup... thats 16.8A draw on a battery with a 10 amp limit... You see what I'm getting at, by being hard on him? its really not safe, what he's doing. not at all.
> 
> Also.. and i could be wrong here, but I don't think its outside the realms of possibility that he's going to discharge the batteries too far, that plus the massive drain on them is a time bomb as far as I'm concerned.
> 
> 
> This site does all the math for you. http://www.steam-engine.org/batt.asp


 
I believe how you use it is just as important as how you build it. Holding the button in for 2 seconds vs 10 seconds is going to make a difference, no?

Reactions: Agree 1


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## n0ugh7_zw

Would totally make a difference. Was just thinking of my own noobish tendencies, and how i like to have a thin layer of safety around what i do.

Reactions: Agree 1


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## n0ugh7_zw

@JakesSA My understanding was that he's running 2 X 0.5 ohm coils.


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## bjorncoetsee

n0ugh7_zw said:


> @Alex, fair enough, but thats a bit of a dicey prospect for a noob, no? Also 0.5 ohms @ 4.2v (max one of those batts will put out when they're fresh off the charger) is 8.4A...
> 
> This guy is running 0.5 ohm dual coils... so actually a 0.25 ohm setup... thats 16.8A draw on a battery with a 10 amp limit... You see what I'm getting at, by being hard on him? its really not safe, what he's doing. not at all.
> 
> Also.. and i could be wrong here, but I don't think its outside the realms of possibility that he's going to discharge the batteries too far, that plus the massive drain on them is a time bomb as far as I'm concerned.
> 
> 
> This site does all the math for you. http://www.steam-engine.org/batt.asp


No no its 1 ohm come each coil, that makes 0.5 together..

Reactions: Like 1


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## n0ugh7_zw

@bjorncoetsee sweet, then you're safe, check out that site I linked, it lets you check what draw your builds will put on the battery.


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## Andre

JakesSA said:


> Insofar research is concerned, the best site I've found is here. He tests batteries with a view to use in flash lights so his concern is more with continuous discharge. In reality this doesn't accurately reflect vaping battery usage but rather something like a 'jammed fire button' condition on a mech.
> 
> The linked page allows you to compare different batteries at different current draws. Under the drop down is also a link that will take you to the full review of the battery.
> 
> As an example here is the discharge curve of the 3100 Efest vs the AWR, these were taken from the detailed test pages.
> Note that the discharge is continuous and measured over a set amount of time at different currents (the colours) with two batteries, A and B as listed in the legend. Two batteries are tested to ensure the test gives consistent results. The test stops when the battery voltage (under load) reaches 2.8V, the minimum safe value.
> 
> View attachment 11429
> 
> 
> What you can deduce from these charts, for example, is that:
> 
> At 10A the 3100 Efest will fire continuously for 10 minutes at which time the battery voltage (under load) will reach 3.2 volts.
> At 10A the AWR will reach 3.2 volts (under load) in what looks like about 6 minutes, again under a continuous fire condition.
> 
> Lastly, what does this mean in Ohms? Well Ohms law says that 4.2V and a 0.42 Ohm coil produces 10A . Note I use the highest possible battery voltage for the calculation.


 
I presume you do not recommend that one can safely use a 0.42 ohm coil on a 10A battery with this info? That would be counter to the advice of several experts.

Reactions: Agree 1


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## n0ugh7_zw

May as well link to this post too. Turns out there is a safe polarity

As far as I'm aware one of the only "safe batterie" for super sub ohming (less than 0.2 ohms) is the Sony 26650, which has a 50A limit.


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## JakesSA

Not so much a recommendation as an example of the info that can be found. The thread author describes a situation which is supported by the graphs.

My opinion on the matter is not so much a safety concern but rather that running batteries close to their rated capacities will dramatically reduce the life of the battery, blow a hole in your wallet so to speak...
I'll stick to about 0.7/0.8 with the 3100s, of course this is no longer considered sub-ohm anymore .. 

@Andre I hear what you saying but I need empirical evidence which Badtitude of the table above is a little thin on, as far as I could find. It is widely quoted though so I might just not have hit the right place with google.

The problem with the detailed info available on the net is that its not really focused on vaping, the information simply isn't detailed enough but rather focus on continuous current drain over long time spans. Important for torches and jammed fire buttons.

I hope to rectify this as soon as time allows with a purpose built battery tester which will emulate vaping specifically. Said battery tester will also hopefully be independently verified as working correctly by the resident forum expert on such matters .... who hopefully will read this and graciously agree without bringing me his car to wash every weekend.

BTW, I heard from another large OEM battery supplier today that there are still no Sony VTCs in our near future. Fakes do however continue to proliferate. 

Please note that I am a retailer and sell the 3100 mAh Efest and therefore my opinion may be biased even if only subconsciously so.

Reactions: Like 4


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## Andre

JakesSA said:


> Not so much a recommendation as an example of the info that can be found. The thread author describes a situation which is supported by the graphs.
> 
> My opinion on the matter is not so much a safety concern but rather that running batteries close to their rated capacities will dramatically reduce the life of the battery, blow a hole in your wallet so to speak...
> I'll stick to about 0.7/0.8 with the 3100s, of course this is no longer considered sub-ohm anymore ..
> 
> @Andre I hear what you saying but I need empirical evidence which Badtitude of the table above is a little thin on, as far as I could find. It is widely quoted though so I might just not have hit the right place with google.
> 
> The problem with the detailed info available on the net is that its not really focused on vaping, the information simply isn't detailed enough but rather focus on continuous current drain over long time spans. Important for torches and jammed fire buttons.
> 
> I hope to rectify this as soon as time allows with a purpose built battery tester which will emulate vaping specifically. Said battery tester will also hopefully be independently verified as working correctly by the resident forum expert on such matters .... who hopefully will read this and graciously agree without bringing me his car to wash every weekend.
> 
> BTW, I heard from another large OEM battery supplier today that there are still no Sony VTCs in our near future. Fakes do however continue to proliferate.
> 
> Please note that I am a retailer and sell the 3100 mAh Efest and therefore my opinion may be biased even if only subconsciously so.


 
Great response, not biased at all imo, thanks. And I agree with your recommendation of 0.7 ish on the Efest 3100s. Looking forward to your battery tester results.

Reactions: Like 1 | Agree 1


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## MorganSa

Dude, relax...I'm confused on subohm all the time. But the aspire atlantis tank is just amzing that I would not even worry about the rebuilding thing, I just pick the atlantis+its cf subohm mod. Avaiable on http://www.heavengifts.com/Aspire.html or http://www.vapeclub.co.uk/clearomiser-tanks/aspire-atlantis-tank.html , do read this review by grimmgreen http://www.grimmgreen.com/post/102171839048/the-new-aspire-atlantis-tank-its-good-i


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