need help with safetyy!

[Cloudn00b23]

Hey guys, I had recently bought a dripper and started building new coils. I've done alot of research and had one of my vape shop buddies set it up for me. I'm running a pegasus mod with a Derringer mod clone on top. I have an efest imr 18650 3.7 volt, 2500mAh battery in it. Would I be safe doing a dual coil .5 ohm build in it? Please help, thanks! also any tips for dual coil builds?

 

[Susan~S]

Hello and welcome to the forum @Cloudn00b23. Glad to have you here!

If your battery is the purple Efest 2500 mAh, it is a 20A CDR battery (not 35A as is printed on the wrapper).

When considering how low you can build you need to give yourself some headroom. I try to never exceed 50% of the CDR (continuous discharge rating) of a fully charged battery (4.2v). So with a 20A battery, that would be 10A. This Ohm's Law Calculator tells me that a .4 ohm build is as low as I would want to use.

The reason that I place a 50% limit is because as a battery ages the mAh of the battery degrades, as the mAh degrades so does the batteries c rating (amp limit). So down the road, a 20A battery may only be a 10A battery.

If you are new to mech mods and/or rebuildables I highly recommend you spend some time with @Baditude & @Mooch (two of our resident battery/safety experts) and visit their blogs. You are now 100% in control of your own safety (and others around you). Make sure you purchase an ohm reader and a voltmeter or DMM so you can measure your builds, check for shorts and measure the remaining charge on your batteries.

Here are links to some of Mooch's blogs:
* Links to all his battery tests to date: List of My Battery Tests | Mooch's Blog
* Picking a Safe Battery to Vape With: Table of 18650 Battery Safety Grades | Mooch's Blog

Baditude's Blog - Table of Contents: The blogs that address battery safety, Ohm's Law, CDR (continuous discharge rating/Amps) and how they all work together are detailed below:

BATTERIES

Battery Basics for Mods: IMR or Protected ICR?
* Another essential read to understand which batteries are safe to use in mechanical and regulated mods. Includes a frequently updated list of recommended safe-chemistry, high-drain batteries with their specifications.

Purple Efest Batteries not as Advertised
* A cautionary blog that reveals that the purple Efest batteries may not have the specifications advertised. Also includes a commentary on "continuous discharge ratings" vs "pulse discharge ratings" of battery specs.

OHM'S LAW

Ohm's Law for Dummies (Vapers)
* My attempt at explaining Ohm's Law in layman terms and how it relates to vaping.

Explain it to the Dumb Noob: Ohm's Law Calculations
* As simple as it is to use, some people have a tough time grasping the concept. Warning: Includes graphic photos of mod explosions.

BATTERIES - WHERE TO BUY

Only buy batteries from a reputable supplier (not ebay or Amazon) as there are many counterfeit batteries being sold. Here are several reputable battery suppliers in the US.

* RTD Vapor
* Illumination Supply
* Lighthound
* Orbtronics

 

[RandyF]

.5Ω is perfectly fine with that battery.

Here is a link to Steam Engine, there you can plug in the numbers and see where your setup stands.

While that battery is fine, it is always advisable to buy batteries that are not re-branded, like the VTC 4/5, LG HE4 or 25r's, branded batteries like the Efest are just re-wraps of.....something, sometimes good, sometimes bad, and always buy them from a reputable source like RTD vapor.

 

[opticruby]

Hello @Cloudn00b23. Welcome to ECF.

Your amp draw on that battery at 0.5 ohms will be around 8.4 amps. So yes you'll be ok. I would'nt go any lower though on efest batterys but .5 will be fine.

Dont forget to test it on a ohms reader after its been wicked, juiced and you've put the topcap on to make sure its not shorting out.

+1 for being safe and asking.

 

[Susan~S]

Your amp draw on that battery at 0.5 ohms will be around 8.4 amps. So yes you'll be ok. I would'nt go any lower though on efest batterys but .5 will be fine.

Saw this video recently put out by Portugal reviewer DJLsb Vapes on his purple Efest 38A 2800mAh battery. HIs battery vented/exploded at 14A.

Efest 18650 Battery Venting at 14Amp and Exploded

 

[opticruby]

Yeah there is a couple of vids about the 38a 2800mah batterys. I was reading mooch's comments on them but the op said he's running 2500mah so I figured it was the 35a rewrapped lg's.

Personally I use the 35a in low wattage devices and thats only because I have them left from old stock.

 

[suprtrkr]

Hi and welcome to the board. @Susan~S and @RandyF have already posted the links I would have given you; I advise you to have a look at them as most of what you need to know is there. I am not fond of Efest rewrap batteries. You never know what cell is under the skin. However, @Mooch has tested the purple ones and finds them safe out to 20 amps, so a .5 build should give you about a 50% safety margin. That's a good place to be, you ask me. I wouldn't go any lower. Being a mekkie from way back, I also predict you'll find an excellent dripper vape in the .5-.7 ohm range. Warm, thick and flavorful. I currently have my Dark Horse built at .65 and it's a beast with the chuff cap. The flavor makes my eyes water and it's hard to see the screen when I exhale

For duals, a few rules of thumb: you want those coils to be as close to identical as you can make them. They don't work well otherwise. Electricity takes (proportionally) the path of least resistance. If one coil is less resistive than the other, most of the power goes to that one and less to the other. The way to tell is when you dry fire them after building and before wicking. They should get hot at the same time and glow the same color. If one gets hot faster than the other, or glows more brightly, you have a problem. It's often uneven tension on the post screws, so check that first. A loose connection can lower resistance, or divert power to the coil leg instead of the body. Remember also parallel resistances total half the value of each side. That is for .5 ohms, you build each coil 1 ohm, not .25 ohm. If you don't have an ohmmeter, you need one.

Kudos to you for being smart enough to understand there are safety issues involved and coming to ask the folks who know how. It may be you have a great vape shop with knowledgeable and safety conscious people. I hope so. But we hear a lot of bad advice from vape shops populated by cloud chasers who can't spell Ohms Law repeated here also. If you are told something that sounds fishy, or that is contradictory to what you're getting here, remember a) we don't have anything we're trying to sell you and b) it costs nothing but a little delay to come and talk to us before trying it. Vape safe, vape happy and vape on!

 

[opticruby]

we don't have anything we're trying to sell you

Exactly this. We're just here to help and advise. Not take your money.