Safe?

[nehctik]

I'm new to rebuildables and mods etc, Ive got myself a nemesis clone, a kayfun lite clone and a igo w7. I'm using purple efest 2500mAh IMR 18650 batteries. Pictured below.




My  question is is there a limit to how low I should build my coils? Like a certain resistance I shouldn't go below?

[Arcturion]

Hi nehctik and welcome to AAEC

As for your questions, there are plenty more experienced peeps on here and I'm sure they will chime in but my reaction is that those batteries are fine for most/all sensible purposes. What I mean by that is that you should definitely be using an ohm meter when you're building your coils and that in a Kayfun you really don't want to be going too low anyway. Try and build your coils to around 1.5 ohms to start with until you're comfortable with the process and comfortable with using your Nemesis.

Personally I like my Kayfun Lite at about 1.2 ohm and those batteries will easily handle that. There are some good coiling and ohm/battery guides on the site - I'll see if I can dig up the links for you.

[markm]

Use an Ohms law calculator - the limit on a mech build is determined by the Amp limit on the battery.
You have one of the few batteries that tells you what that limit is on the side, most you need to
find out the C rating and then calculate the safe amp limit.

[ionian]

The Efest purple batteries overestimate the current available - they state 35A on the battery, but I believe the safe continuos discharge (ie when holding the button) is actually 20A. ronaldo can confirm this, he tests these batteries for a living.

The good news is that 20A is safe down to around 0.3 ohm coils (0.21ohms is 20A discharge), which is vaping at 58watts. Unless your throat is made from Teflon, I would imagine that will give you quite the hit

[Arcturion]

Here is the Ohms vs Current guide that I was looking for. As ionian has said, even at 0.3ohm you should be good. Though whether the Kayfun or your throat will stand to up that is another matter!

[hijack]

Aug 20, 2014 18:37:25 GMT ionian said:

The Efest purple batteries overestimate the current available - they state 35A on the battery, but I believe the safe continuos discharge (ie when holding the button) is actually 20A. ronaldo can confirm this, he tests these batteries for a living.

The good news is that 20A is safe down to around 0.3 ohm coils (0.21ohms is 20A discharge), which is vaping at 58watts. Unless your throat is made from Teflon, I would imagine that will give you quite the hit

As ionian says the 35A efest is a rewrapped 20A LG but is perfectly safe to use as a 20A battery. Im using one ATM with a Dripper at .35 Ohm which is 12A

[nehctik]

Im using a ohm reader to build. I just finished tinkering and ended up with 0.70ohm dual coil. I put the resistance and my batteries current charge (3.79v checked with multimetre) it brings up 5.29A. So as I understand it as long as the amp result us lower than 20 using that calculator, it should be safe?

[ionian]

Aug 20, 2014 19:35:32 GMT nehctik said:

Im using a ohm reader to build. I just finished tinkering and ended up with 0.70ohm dual coil. I put the resistance and my batteries current charge (3.79v checked with multimetre) it brings up 5.29A. So as I understand it as long as the amp result us lower than 20 using that calculator, it should be safe?

Yes in theory. My advice would be don't push it to its 20A limit, keep some margin for error on the battery makers part. 

Edit: but yes, your current build, assuming no shorts, is safely within the capabilities of your battery. 

[nehctik]

Ok, I understand this a bit better than I did before now. Thank you for your help guys and or gals.

[ronaldo]

Brilliant and I now know that people are getting educated from what I write on here yes the purple e-fests 35A are really 20A I always personally like to disregard 10% for safety purpose so I would treat them as a 18A battery and with a 18A battery you can go low but it looks like you all are starting to learn that battery safety is important keep up the good work as it looks like my job is done

[nehctik]

OK another question about batteries and charging, I read somewhere its time to charge when it gets down to around 3.3v is this correct as I don't want to knacker my batteries.

[ionian]

3.3v is a safe voltage to change batteries, but I wouldn't let it go much lower than that. For me, the vape becomes a little too weak at around 3.5v so that's when I usually make a change. I use coils around 1ohm.

[VapingBad]

3.3 V would be OK if your not pushing the power much, if you are running at high wattage/ampage I would change them more around 3.5 - 3.6 V as you need to take into account the voltage drop under load, high drain batteries don't have such a large voltage drop as standard so add a bit for standard IMRs. If you have a tanko-metre you can check the voltage drop on your set up and 3.3 V makes the most sense this way as the time to change.

A CGR (10 Amp, Int res 0.05 ohm) battery at 3.5 V with a 1 ohm load when new will drop to about 3.325 V.
A CGR (10 Amp, Int res 0.05 ohm) battery at 3.5 V with a 0.5 ohm load when new will drop to about 3.150 V.