# Double Stack Batteries



## Hein510

So me and @Bartho have been discussing double stacking batteries.

Every vaper has completely banned doing this but I worked out that if you are running 2x 18350 (Giving say 8Volts) batteries in a Nemi with a 1Ohm coil, it will come out to 64watts with a amp draw of 8amps. 

Running 2x 18350 Efest purple batteries I would say its still safe as they are rated to 10.5amps.

What does the electronic pros say about trying this out?


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## Andre

Everywhere I have read people have advised against stacking batteries, but I am not an expert in this field. That safety margin seems too slim for me. Question is, why do you want to do it?

Reactions: Agree 1


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## Gazzacpt

I don't think it's a current draw issue more arcing between batteries and they should be matched pairs. Since its used close to your face I wouldn't risk it. I've heard of more cases of stacked batteries going wrong than single batts. And thats in torches.

Sent from my GT-I9190 using Tapatalk

Reactions: Like 1


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## Hein510

Purely wanna try it for the gain in watts!

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## Derick

Plenty have done it and they reckon it is completely safe - then there are those few that now miss chunks of their cheeks and tongue's - they used to be of the group that said it is safe - not so much anymore.

So your face, your risk 

The problem as is stated, is that the connection between the batteries by just stacking them is not really sufficient to carry a proper current - remember these are not 1.5v AA batteries you are stacking here, but 3.7V with waaay more amps than any AA.

So arcing can happen, or the connection is just not very good and causes a heat buildup - and boom, you have an extra hole to breathe through in your face.

Remember that those battery packs they make for lap-tops etc. are 18650's soldered together with low-resistance leads - they learnt long ago not to stack.

So your risk, but I recommend taking lots of pictures of your face from various angles - so that the plastic surgeons have nice reference photos when they have to rebuild your face

Reactions: Agree 4 | Funny 1


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## johan

Agree with what @Derick said - potential arching leads to overheating and then you have major sh@t!


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## 360twin

My SVD instruction manual actually recommend_s_ stacking two 18350 batteries:

"You can use 2 IMR high drain 18350 batteries at the same time, which will give you the full arrange of voltages/Wattages and proper power needed to use the device."

I don't think the connections between the batteries would be any worse than those between the battery poles and the casing, but this device does have a screw thread adjuster to ensure good contact pressure. I have no reason to try it though.


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## drew

Most devices are designed with vent holes on the bottom should something go wrong. If the top cell in a stacked configuration vents there is no way for pressure to escape... a pipe bomb comes to mind.

Reactions: Agree 1 | Informative 1


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## 360twin

@drew True, but in the case of the SVD the space between the battery and the casing is a greater area than the vent holes in the base. The upper battery should be able to vent past the lower one. Still wouldn't try it though as I can't see the point - it's limited to 5A anyway.

Your analogy of a pipe bomb brings to mind me telling my staff about my fAW batteries - when they asked what the issue was, I explained; 'Imagine putting this thing in your mouth with an unknown battery inside, and then pushing the fire button ...' The looks of realisation said it all

Reactions: Like 2


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## Xhale

while I have no firsthand experience of this, I have heeded the warnings given by others, but on the understanding that the danger is not to do with arcs or anything to that effect, but due to the cells themselves differing slightly in capacity/voltage.
The "best practise" is to buy the two batteries at the same time, from the same place, label them as a pair, i.e. A1 and A2, use them together in the same configuration, charge at the same time etc. Treat them as one battery.

That minimises the risk.

The risk is here
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20100037250.pdf
pages 25, 26, 27
test done on 18650 batteries

If one cell is lesser in capacity than the other, and you approach the voltage where the cells would cutoff, its gets exciting

I like vaping, but not exciting vaping

Thats said, many box mods happily run dual 18650's and it seems to work ok.
Interestingly, the smok VMAX is designed to use two 18350 cells, so at least one manufacturer has said "bugger this" and made it work, or perhaps our fears are unfounded.
I would stick with IMR if my face was at stake.

Reactions: Informative 1


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## ET

i would be one of those "loons" keen to try it at some time with the right batteries. the batteries we use don't actually explode, there is always a gets hot before the poo really hits the fan time and that should be more than enough time to lob your device at the nearest person you don't like. 
added to that you are more likely to die in a car accident on the way to work. 
hmmmm 64 watts nomnomnom

Reactions: Funny 2


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## johan

Vern said:


> while I have no firsthand experience of this, I have heeded the warnings given by others, but on the understanding that the danger is not to do with arcs or anything to that effect, but due to the cells themselves differing slightly in capacity/voltage.
> The "best practise" is to buy the two batteries at the same time, from the same place, label them as a pair, i.e. A1 and A2, use them together in the same configuration, charge at the same time etc. Treat them as one battery.
> 
> That minimises the risk.
> 
> The risk is here
> http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20100037250.pdf
> pages 25, 26, 27
> test done on 18650 batteries
> 
> If one cell is lesser in capacity than the other, and you approach the voltage where the cells would cutoff, its gets exciting
> 
> I like vaping, but not exciting vaping
> 
> Thats said, many box mods happily run dual 18650's and it seems to work ok.
> Interestingly, the smok VMAX is designed to use two 18350 cells, so at least one manufacturer has said "bugger this" and made it work, or perhaps our fears are unfounded.
> I would stick with IMR if my face was at stake.



Just my 2c:

Agree with your statements and the attachment is a very good article - just for clarification:

1. In the case of high current draw (ie sub-ohming) any form of arching creates heat and cavitation on the battery contacts in the long-run which leads to a pretty nasty mess.
2. Running batteries in parallel is totally different from running them in series.
3. Most of our statements on this forum is "over exaggerated" and highly conservative to protect the non-technical user against any potential mishaps.

Reactions: Like 1 | Agree 2


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## Derick

johan said:


> Just my 2c:
> 
> Agree with your statements and the attachment is a very good article - just for clarification:
> 
> 1. In the case of high current draw (ie sub-ohming) any form of arching creates heat and cavitation on the battery contacts in the long-run which leads to a pretty nasty mess.
> 2. Running batteries in parallel is totally different from running them in series.
> 3. Most of our statements on this forum is "over exaggerated" and highly conservative to protect the non-technical user against any potential mishaps.



The last point is for me why I warn against it - yep the technical guy out there that knows how batteries work, has had experience in batteries getting hot and venting and knows what to do when they do go into thermal runaway , that guy will ignore my warning and stack them and be safe about it and be perfectly fine.

It's the other dudes/dudettes I worry about

EDIT: Besides, these days with 35A batteries easily available, I fail to see the need for stacking

Reactions: Agree 3


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## RezaD

I think in the case of an SVD or any other digimod limited to 5A it is safe when using high current draw batteries like the Efests and genuine AW's.

This precaution is for mech mods where some looner stacks 2 fake AW batts on a 0.1 Ohm coil and then wonders what went wrong.


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## BhavZ

RezaD said:


> I think in the case of an SVD or any other digimod limited to 5A it is safe when using high current draw batteries like the Efests and genuine AW's.
> 
> This precaution is for mech mods where some looner stacks 2 fake AW batts on a 0.1 Ohm coil and *then wonders what went wrong*.


If he is still alive to wonder


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## ET

RezaD said:


> I think in the case of an SVD or any other digimod limited to 5A it is safe when using high current draw batteries like the Efests and genuine AW's.
> 
> This precaution is for mech mods where some looner stacks 2 fake AW batts on a 0.1 Ohm coil and then wonders what went wrong.



darwinism at it's finest


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