Lets talk safety!!!

[bebeau25]

I'm posting this for my own reassurance and for others interested in coil building. I recently got an rba, started playing around with it, and have had decent results. I did some research and found other people talking about their setups and decided it was safe to go ahead and pretty much copy what they are doing. Probably not the safest way of doing things. It kind of bothered me that I didn't know, with some kind of hard evidence, that what I am doing is safe, so back to ECF and youtube I go. This will be old news for a lot of you, but feel free to chime in with any info that you would like to add. It didn't take long and I came across the ohms law calculator. Wonderful little tool. Did some research on the batteries I'm using and this is what I came up with.

AW IMR 18350 700mAh 3.7 V specs

Nominal Voltage: 3.7 V
Capacity: 700mAh
Lowest Discharge Voltage: 2.50V
Standard Charge: CC/CV (max. charging rate 2A)
Cycle Life: > 500 cycles
Max. Continuous Discharge Rate: 6A

Using Ohms Law Calculator, Ohm's Law Calculator Here are the results,

Voltage: 4 (freshly charged battery)
Current: 5.71429
Resistance: 0.7
Power: 22.85714

Voltage: 3.7
Current: 5.28571
Resistance: 0.7
Power: 19.55714

So according to these numbers (and please correct me if I'm wrong) the battery has a 6A discharge rate, and the numbers come to 5.7 @ 4V and 5.2 @ 3.7V which makes this setup a "safe vape".

AW IMR 18650 3.7V 2000mAh specs

Nominal Voltage: 3.7 V
Capacity: 2000mAh
Lowest Discharge Voltage: 2.50V
Standard Charge: CC/CV (max. charging rate 2A)
Cycle Life: > 500 cycles
Max. Continuous Discharge Rate: 10A

With a 10A discharge rate these batteries would be safe with this setup as well.

To anyone that has a better understanding of all this, please correct anything that I've done wrong and add any helpful information to keep all of us safe while diving into this new found hobby.

 

[CloudZ]

Yep, you got it right. If you stay under the safe amperage with theoretical calculations, there should be no problem due to voltage drop. So the actual voltage the battery is putting out will be lower than what you measure with a multimeter because the mod and battery itself have some small internal resistance. Thus, lower amps. Its not as safe when you actually factor in the voltage drop and try to push right up to the amp limit with even lower resistance.

So lets say my battery comes off the charger reading 4.2V and my coil is 0.5 ohms. Theoretically, that is 35 Watts at 8.5 amps. My batteries can handle up to 10A. So in theoretical fantasy land, even that is safe. Now, if you consider that I am getting 0.4V drop at that current draw (its probably considerably more than that with my cheap mechs), I am actually operating at 3.8V, which is only 29W at 7.6A. Lets say I measure my voltage drop and decide to play with fire. I drop my resistance down to 0.4 ohms, and assuming the drop is still the same (it would actually be a bit more), now I am at 9.5A. That's how sensitive it is, 0.1 ohms less and you're pushing the limit.

So be safe, know exactly what the electricity is doing with a decent multimeter, and use theoretical calcs to stay under the battery limitations.

 

[Ryedan]

I agree you are on the right track bebeau. One thing that is incorrect - a freshly charged battery will run between 4.15 and 4.25 volts. Most chargers will stop charging very close to 4.2. At 4.25 volts and 0.7 ohms, you will be drawing 6.07 amps, a bit over your smaller batteries capacity. A short will make the resistance go down, taking the amps way above what these batteries can handle. This is not safe.

I run a mech mod and AGA T with 0.7 ohm coils drawing the 6.07 amps we already established for these numbers. I use batteries rated for 10 amps and this has been safe for me since February this year. I regularly check battery volts and coil resistance with a multimeter. Vape safe and enjoy!

 

[bebeau25]

Thanks guys...all good information here. Ryedan I appreciate the correction on a freshly charged battery. I'm kind of a numbers guy, so I love having the information so readily available using ohms law calculator.

Sent from my DROID RAZR using Tapatalk 2

 

[classwife]

Thanks guys...all good information here. Ryedan I appreciate the correction on a freshly charged battery. I'm kind of a numbers guy, so I love having the information so readily available using ohms law calculator.

Sent from my DROID RAZR using Tapatalk 2

Good !
Adding a calculator to your thread !

Online Conversion - Ohm's Law Calculator


Ok...gonna go get more coffee !
I see it is in the first post !

 

[bebeau25]

Lol...I can't think straight without a few cups of coffee either.

Sent from my DROID RAZR using Tapatalk 2

 

[Steam Turbine]

Correct me if i'm wrong but I believe that firing your battery at exactly or a little under it's amp limit will reduce the overall life of your battery.

 

[Ryedan]

I believe you are correct ST. Actually, pushing a battery to any limit will stress it and shorten it's life. Fast charge, over charging, running to almost empty and running hot all come to mind. It's amazing how few people know this.

 

[Baditude]

I believe you are correct ST. Actually, pushing a battery to any limit will stress it and shorten it's life. Fast charge, over charging, running to almost empty and running hot all come to mind. It's amazing how few people know this.

And users come here wondering why they are only getting 2 hours time on their battery.