Whats the lowest we should go on those efest "35" amp 18650 batteries?

[Haadkoe]

Just wondering what the lowest ohm build we can safely push on a single efest "35" amp battery in a mech?

The shop I bought my gear from (including the batts) originally wrapped me a dual coil build at .15 ohms. On my first build at home I ended up hitting .2 ohms.

...then I started wondering if I'm at risk of blowing myself up.

Thoughts?

 

[Monotremata]

Lower ohms doesn't really matter, all that does is lowers the voltage needed. The real question is how many watts are you running at? That's what you need to be concerned with. More watts/more voltage require more amps. Plenty of calculators out there to do the math for you.

And once again, as has been posted here many many times, those are rewrapped LG HE2s they are NOT, and I repeat NOT, a 35 amp battery. That's a pulse rating. Those are 20 amp continuous batteries and should be treated as such. If you think you've got 35 available at all times, then you need to worry..

 

[Dampmaskin]

Technically,

R = U / I.
R = 4.2 V / 20 A
R = 0.21 Ohm.

But realistically, we want some headroom (factor of safety). So let us say that 20% is safe enough (but is it?)

R = 4.2V / 16 A.
R = 0.26 Ohm.

That's the absolute lowest I personally would go with those batteries, if I was feeling adventurous. But if I were to vape at 0.26 Ohm regularly, I'd probably go looking for a mod that allowed me to run two 18650s in parallel. Not just for the added safety factor, but for the added vape time as well.

 

[pt91]

IMO .3 or higher.

 

[Haadkoe]

Lower ohms doesn't really matter, all that does is lowers the voltage needed. The real question is how many watts are you running at? That's what you need to be concerned with. More watts/more voltage require more amps. Plenty of calculators out there to do the math for you.

And once again, as has been posted here many many times, those are rewrapped LG HE2s they are NOT, and I repeat NOT, a 35 amp battery. That's a pulse rating. Those are 20 amp continuous batteries and should be treated as such. If you think you've got 35 available at all times, then you need to worry..

That's why I had the 35 in quotation marks. I know thats the pulse rating and that they're actually 20 amp continuous rated LG's... Ive read that at least a hundred times, it's the rest of the math which has eluded me.

I'm using a mech mod, so I don't have the luxury of a wattage display. Its up to me to wrap safely, and obviously that shop I had originally gone to wasn't doing me any favors with that .15 build.

Technically,

R = U / I.
R = 4.2 V / 20 A
R = 0.21 Ohm.

But realistically, we want some headroom (factor of safety). So let us say that 20% is safe enough (but is it?)

R = 4.2V / 16 A.
R = 0.26 Ohm.

That's the absolute lowest I personally would go with those batteries, if I was feeling adventurous. But if I were to vape at 0.26 Ohm regularly, I'd probably go looking for a mod that allowed me to run two 18650s in parallel. Not just for the added safety factor, but for the added vape time as well.

IMO .3 or higher.

Excellent, thanks for the info and advice.

Any suggestions for one of those calculators to help me figure this out on my own in the future?

 

[Dampmaskin]

You can try the one in my signature.

 

[Haadkoe]

You can try the one in my signature.

Lol, I was literally just looking at that the moment after I hit submit. Awesome resource you've made for us there! Thanks a million!!!!!

 

[ThePaladin]

That's why I had the 35 in quotation marks. I know thats the pulse rating and that they're actually 20 amp continuous rated LG's... Ive read that at least a hundred times, it's the rest of the math which has eluded me.

I'm using a mech mod, so I don't have the luxury of a wattage display. Its up to me to wrap safely, and obviously that shop I had originally gone to wasn't doing me any favors with that .15 build.





Excellent, thanks for the info and advice.

Any suggestions for one of those calculators to help me figure this out on my own in the future?

Ohm's Law Calculator

Cheers!

-P

 

[Haadkoe]

Ohm's Law Calculator

Cheers!

-P

Thank you as well.

 

[Dampmaskin]

Also be aware that the amp rating is for new batteries. As the batteries age, their ability to handle amps drops.

How soon, and much, you cannot know - unless you've got some badass equipment and know-how.

 

[jj6404]

Also be aware that the amp rating is for new batteries. As the batteries age, their ability to handle amps drops.

How soon, and much, you cannot know - unless you've got some badass equipment and know-how.

Can you say at all a ballpark estimate of how long before that amp rating drops with new batteries? And by how much it drops?


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[Dampmaskin]

No, sorry. It depends on the make of the battery, how hard they've been (ab)used, individual variances, etc., etc.

I don't even know how much own batteries have deteriorated. So I try to play safe.

A sort of consensus around these parts seems to be that one should leave a 50% headroom in order to stay safe in the long term. In other words, if the batteries are rated for 20A, don't pull more than 10A from them. But your mileage (and risk aversion) may vary.

 

[jj6404]

No, sorry. It depends on the make of the battery, how hard they've been (ab)used, individual variances, etc., etc.

I don't even know how much own batteries have deteriorated. So I try to play safe.

A sort of consensus around these parts seems to be that one should leave a 50% headroom in order to stay safe in the long term. In other words, if the batteries are rated for 20A, don't pull more than 10A from them. But your mileage (and risk aversion) may vary.

I was told by a respectable and knowledgeable safe vaper that 20% head room, say about a 0.3 ohm build in a 20A CDR batt like the purple 2500 mah efest was comfortably safe.

If my aforementioned question was too difficult to answer (understandably), then maybe this one can be answered more assuredly: if one were to run such builds with 20% head room often, how long before one should get new batteries to remain relatively safe?


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[crxess]

Cycle your batteries at 3.6v and they should last a near normal life span.

Remember, a battery designed to output 20a should be able to do so until depleted to its safe minimum discharge. 20a would be the maximum continuous discharge rate. Not a 4-10 second burst. A LOT of people around here misunderstand this.

Just remember a 2500mah battery running continuously at 20a is going to deplete rather quickly.

 

[jj6404]

Cycle your batteries at 3.6v and they should last a near normal life span.

Remember, a battery designed to output 20a should be able to do so until depleted to its safe minimum discharge. 20a would be the maximum continuous discharge rate. Not a 4-10 second burst. A LOT of people around here misunderstand this.

Just remember a 2500mah battery running continuously at 20a is going to deplete rather quickly.

What do you mean by cycle your batteries?

I don't have a multimeter (bad, I know) but I basically use a fresh batt in my mech all day at work which means about 4-5 vape sessions (0.35 ohm dual coil build) and when I get home I switch to a fresh and put it on the charger.


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[jstrong]

I was in a local shop today buying some juice. I don't buy any mods from a B&M because they charge too much. As I was standing there talking a guy comes in and wants a mech mod. You could tell he didn't know anything about a mech. He proceeds to ask which batteries to get. I look over and the shop had some VTC4's, Purple Efest, and some LG HE2's. I told him it would be a smart move to get the Sony VTC4 and to have the 30A to be on the safe side. The guy at the shop holds up that Purple Efest and shoves it in my face and says BOOM, this is 35A with a higher mah rating. I was so freaking annoyed. Guess which battery the guy bought. The Efest I have yet to see why people love these batteries. To me Efest is the Cloupor of batteries. Reminds me of a Meghan Trainor song, They Lie, Lie, Lie

 

[edyle]

I was told by a respectable and knowledgeable safe vaper that 20% head room, say about a 0.3 ohm build in a 20A CDR batt like the purple 2500 mah efest was comfortably safe.

If my aforementioned question was too difficult to answer (understandably), then maybe this one can be answered more assuredly: if one were to run such builds with 20% head room often, how long before one should get new batteries to remain relatively safe?


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Lithium type batteries are supposed to be good for about 300 recharges.

 

[jj6404]

Lithium type batteries are supposed to be good for about 300 recharges.

So does that mean 300 recharges until the continuous discharge amp rating drops from 20? Or 300 recharges until it's basically unusable?

And if I charge my batteries very often, like basically keep them topped off, would those even count as full "recharges"?


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[edyle]

So does that mean 300 recharges until the continuous discharge amp rating drops from 20? Or 300 recharges until it's basically unusable?

And if I charge my batteries very often, like basically keep them topped off, would those even count as full "recharges"?


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unuseable.