Revisiting an old battery question

[CloudyDayz]

Hey guys, finally decided to make an account after many months of just visiting. Anyway i'm not new to the vape scene. started over a year ago with a vamo, Loved it but decided i wanted some sub-ohm action so 2 months ago i picked up a chi-you and a maraxus with a plumevail and patriot to match. so here it goes.

ive been reading a ton of posts about stacking 18350s and how is not save as its extremely easy to overload the batteries. after researching the set that i have they are ICR 18350 900Mah 3.7v. Max discharge of 2c(20A).
if i stack these on a .4 ohm coil im only using 18.5 amps. seeing as this is under the max rating of 20A, is it safe to do?
yes i have a sony vct5 which i currently use in the mechs.. but i hate to see these little guys go unused if they could have the potential to put out 140w

 

[dice57]

Umm, NO, NONONONONONNONNNOOOOOONONNONNN NO

NO

NO don't do it. No if you want to break 100, there are safer ways to do it,

No

 

[Baditude]

What is the brand name of those 18350 batteries? If they are ICR batteries, they will only have a continuous discharge rating of no more than 2 or 3 amps. There are no 18350 batteries on the market with 20 amps continuous discharge rate, whether they are ICR or IMR chemistry.

Therefore, even though I never advocate stacking any batteries, I most definitely recommend you NOT STACK those batteries.

I don't know how you came up with the 18.5 amp figure, but it's wrong. A 0.4 ohm coil will pull 10.5 amps from the battery source. Regardless, you'll have less than 3 amps from the 18350 ICR's. This is a sure bet to set up a major battery catastophy.

I will also ask why you would want to stack batteries in the first place? To what gain? Stacking doubles voltage, but not amperage nor capacity (mah).

What you are contemplating is highly NOT ADVISEABLE. Don't do it man!

 

[InTheShade]

Highest continuous discharge rated 18350 batteries that I know of are the efest purple 700 IMR's at 10.5 amps.

I find it hard to believe you have 20 amp 18350 batteries.

When you are using them, they are going to be about 5 inches from your face - are you willing to take the risk? I wouldn't.

 

[PapaSloth]

Stacking doubles voltage, but not amperage nor capacity (mah).

Hi Baditude,

Forgive the newbie question, but I thought amperage was voltage divided by resistance. Since stacking batteries doubles the voltage, but the resistance stays constant at .4 ohms, doesn't that mean the amperage would be doubled as well? Or am I missing something about how Li ion batteries work? I'm keen to learn.

Thanks,
-PapaSloth

 

[Baditude]

Hi Baditude,

Forgive the newbie question, but I thought amperage was voltage divided by resistance. Since stacking batteries doubles the voltage, but the resistance stays constant at .4 ohms, doesn't that mean the amperage would be doubled as well? Or am I missing something about how Li ion batteries work? I'm keen to learn.

As I stated earlier, when stacking batteries the voltage is doubled, but the amperage and capacity (mah rating) remains the same. The amperage does not double.

And I repeat, there is no 18350 battery with a 20 amp continuous discharge rating. The highest rated 18350 battery is the purple Efest with 10.5 amps continuous.

Explain it for the Young Noob: Ohms Law Calculators

When you build your coil and fire it on your mod, it will draw a certain current (amps) from the battery. That current must not be more than the total amps in continuous discharge rate of the battery (determined by the manufacturer of the battery), or very bad things could happen. List of batteries and their amp limits

To find out what current (amps) the coil will pull, you use an Ohms Law Calculator.

You have the resistance of the coil (what you measured with your ohm meter) and the voltage (always use 4.2 volts of a fully charged battery), so type those figures into the calculator and then click calculate. The current is the amps that coil will draw from the battery. Not so hard, right?

 

[PapaSloth]

You have the resistance of the coil (what you measured with your ohm meter) and the voltage (always use 4.2 volts of a fully charged battery), so type those figures into the calculator and then click calculate. The current is the amps that coil will draw from the battery. Not so hard, right?

Right, not so hard, but two stacked batteries would be 8.4V, not 4.2V. So, since resistance is fixed, you get twice the amperage of a 4.2V battery (I understand this is way more current than the battery can actually supply, so bad things happen. I'm just saying that if the batteries could supply that much amperage, they would supply twice as much as a single battery, unless I'm misunderstanding something).

-PapaSloth

 

[Baditude]

Yes, you are misunderstanding.

Amperage does not double when stacking batteries, only voltage. You will only have the amps of whatever a single battery has, whether you use one or two batteries.


For example, if one has two batteries (the manufacturer determines the amp rating). Each has 6 amps, 4.2 volts, 500 mah.

Stacking will give you 6 amps, 8.4 volts, and 500 mah.

Volts double. Amps and mah stay the same as if there was only a single battery.

 

[PapaSloth]

I'm genuinely confused because I = V / R. R is fixed. Therefore, when V doubles, I doubles. The only way that I does not double is if either V doesn't double when you stack batteries, or if R doubles. But, it's a fixed coil, so I don't see how R could possibly double.

 

[InTheShade]

In series (which is what 99.99% of all tube mechs use) the voltage is doubled and the amps stay the same. Now if you had the cells in parallel the voltage stays the same and the amperage is doubled.

This link might help.

 

[PapaSloth]

Thanks InTheShade. But, if I = V/R and V doubles but I stays the same, then R must double as well. Where is the extra resistance coming from, since the coil isn't changing? Is it in the batteries themselves?

 

[PapaSloth]

According to this page, Half Batteries Not Half Current which was written for high school students, if you add a battery in series you double the amperage.

 

[Baditude]

I believe you may be confusing battery amps and coil amp draw.

A battery manufacturer determines the amp rating for his battery. Say 10 amps continuous discharge rate.

You determine the amp draw of a coil by using the ohm's law formula.

It really doesn't matter, though, does it? You do not stack batteries to use a sub-ohm coill. You shouldn't stack batteries PERIOD. You use the correct 18650 IMR battery, and make sure it has enough amps for the amp draw that the coil will draw.

 

[rondasherrill]

Thanks InTheShade. But, if I = V/R and V doubles but I stays the same, then R must double as well. Where is the extra resistance coming from, since the coil isn't changing? Is it in the batteries themselves?

Current isn't pushed from the batteries, it's pulled from the atomizer. 8.4v on a 0.5ohm atomizer would attempt to PULL 17 amps from the batteries, but they can only give the original 3 or whatever amps continuously.

 

[Nat79]

I'm genuinely confused because I = V / R. R is fixed. Therefore, when V doubles, I doubles. The only way that I does not double is if either V doesn't double when you stack batteries, or if R doubles. But, it's a fixed coil, so I don't see how R could possibly double.

I think what your trying to look at is the amperage of the circuit you want to use. What these very wise advisors are looking at is the amperage of the cells wich will not match up with your circuit.

 

[PapaSloth]

OK, thanks everyone! I understand now.

-PapaSloth

 

[CloudyDayz]

Well i cant post links... so heres brand / info..
High-Quality-D-K-L-ICR-18350-900mAh-3-7V

 

[CloudyDayz]

also the 18.4 came from 7.4/.4 = 18.5.
on the link for the bats it says 20C.. i assumed that meant 20A? if not then i will definitely not try as i read the links you(Baditude) posted in previous threads and im not really into plastic surgery lol

 

[Rickajho]

Hey guys, finally decided to make an account after many months of just visiting. Anyway i'm not new to the vape scene. started over a year ago with a vamo, Loved it but decided i wanted some sub-ohm action so 2 months ago i picked up a chi-you and a maraxus with a plumevail and patriot to match. so here it goes.

ive been reading a ton of posts about stacking 18350s and how is not save as its extremely easy to overload the batteries. after researching the set that i have they are ICR 18350 900Mah 3.7v. Max discharge of 2c(20A).
if i stack these on a .4 ohm coil im only using 18.5 amps. seeing as this is under the max rating of 20A, is it safe to do?
yes i have a sony vct5 which i currently use in the mechs.. but i hate to see these little guys go unused if they could have the potential to put out 140w

Stop right there. You have a 900 mAh rated battery with a max discharge rating of 2c. That gives you a max discharge of 1.8 amps. Where are you getting the 20A figure from?

It should be obvious right there that you shouldn't be using a battery with a "safe" top end of only 1.8 amps, let alone using ICR, let alone stacking ICR.

 

[CloudyDayz]

i miss typed in my original post. the link for the batteries states 20C