E-Cigarette Forum - APV Discussion

Bottom switch mechanicals: case for reversing battery?

generic mutant — Thu, 23 May 2013 23:18:21 GMT

I've read all the info both on this site, and elsewhere around the web, which says you shouldn't ever reverse the battery. I, and I think most people, take that to mean the body of the mod should be negative.

But I'm staring at my Sigelei #8 and can't get it out of my head that if you leave the atomiser on the mod when you're not using it, it would make more sense to have the plus where the switch is - at the bottom, making the body positive.

In case anyone isn't familiar with the mod, it's a mechanical with a little switch sticking out the side near the base. The switch joins the body to the negative post, and a hot spring joins the post to the battery. Something like this in standard battery position:

Battery + --> Atomiser --> Mod body --> Switch --> Hot spring --> Battery -

So if the battery loses its wrapper, it's bypassing the switch and hot spring. You're relying on the atomiser failing to break the circuit.

Conversely, if you flip the battery, positive at the bottom, you're bypassing the atomiser. Both the switch and the hot spring are still in the circuit (edit - although the hot spring isn't in the right place for gravity to break the circuit...).

Very confused (and probably wrong, I don't understand electrical things)... any help?

Edit - or does this in fact not mean the body is positive at all? The fact that the switch is in between the body and the positive terminal? That would make more sense. If that is the case, and I'm increasingly thinking that's the only thing that can possibly make sense: it seems like something that's not obvious to a new user, and is perhaps something that should be better emphasised in the battery safety threads.

Looking for some good DIY 18650 mods

kurisu — Thu, 23 May 2013 22:21:13 GMT

Got 6 18650s from a bad laptop battery and plan to add protection pcbs to them and looking for something to do with them any suggestions?

Sent from my SCH-M828C using Tapatalk 2

Battery use: a) Buttons and b) Over-discharge

tmoore — Thu, 23 May 2013 18:36:24 GMT

I've been reading a lot of battery stuff today, but there are two things I need to get clear on...

Is there any rule of thumb for knowing if your APV requires a button top or flat top battery? I can see where you might go wrong trying to use a flat top when a button is needed to reach a contact, but wouldn't a button top always work? Or is it always just going to be model specific? FWIW I have two rigs incoming that I'll be using soon to be aquired batteries in. An Evic and a KTS Storm (GG clone)

Next question, is there any protection or indication when an IMR battery is getting to the point of over-discharge in a mech mod? Do you just have to put it on a volt meter period?

TIA

Price on a used eVic

mrveggie — Thu, 23 May 2013 16:59:26 GMT

Hi. A friend has a used evic that he wants to get rid of. He's used it heavily for several months. What is a good price range after the amount of use he has put it through? I don't know much about the resale value of APVs. Thanks.

BAM - Anyone know the outside diameter?

taylormadesuperfast — Thu, 23 May 2013 16:47:01 GMT

I'm making a wood stand for my mods and I currently don't have my BAM (wife has it and is out of town for a few days) I don't want to wait for her to get back so I figured I would ask here to see if anyone knows the outside diameter of the BAM? It would be greatly appreciated!

Thanks in advance!

Precise 18650

Flyer — Thu, 23 May 2013 16:46:57 GMT

Looking for one. Anyone know who might have them? None on classes either at this time.

Find me an 18350 mech mod

the_vape_nerd — Thu, 23 May 2013 16:41:25 GMT

I really want a small mech mod. Here's what I want in one:

1. Stainless steel or other decent metal build quality;
2. Side mounted button;
3. Flat top (no ego threading); and
4. Reasonably priced under $50.

Suggestions?

I've looked at a lot of telescoping ones, they all seems to either a. look weird b. have ego threading or c. have the dreaded bottom fire button.

iHybrid Pure - mass produced at an affordable price?

TroyDestroy — Thu, 23 May 2013 14:45:46 GMT

thoughts? I'm in for one

http://youtu.be/V_OrUvhDzZ0

cant seem to get the youtube video embedded...

Need suggestions on a mod

STLJohnny — Thu, 23 May 2013 13:43:54 GMT

Hello All,

I just started on RBAs looking for a mod to go sub ohm and see how I like that.
Features im looking for.
Small like the k100. This is what I was just about to get but thought I would ask as I know little about my options.
I like the bottom button
price I want to be <$50
I like the looks of k100 or 101 just not sure how it performs
probably telescope so I can keep it small with 18350 but have the option to go larger.

Just found the k100 and 101 in stock for $34 that seems to be the best price Ive seen. If they are worth investing in at all.

Thanks!

New to me Provari!

josvac — Thu, 23 May 2013 03:38:21 GMT

So, two days ago I ordered an Nzonic V3 from vapingace.com. I'm stoked! Today I went into my local B&M to look at Provari's and one of the employees was selling his Provari V1 with the extended cap for $100. What luck! I am so impressed with the Provari I think I'm going to sell my Evic, SVD, Vamo and my Smoove twist to get another Provari. I guess all the hype was true. Thanks to all the ECF members for their thoughts and advice that I have read here in the last few weeks. Vape on! ;o)

Vamo vs iTaste MVP

TxArrow — Wed, 22 May 2013 23:37:53 GMT

Well, I've decided it's time to move up from the eGo-T battery and I've narrowed it down to a Vamo or a MVP. My eyes have exploded from doing research on these two and the pros for both are outstanding from what I've read. Now, I need some more insight from the community. I know the Vamo is very popular, but so is the MVP. It's a good dilemma to be in, I guess. I'm leaning toward the MVP, even though it doesn't go to 6 volts, doesn't do watts and the lacks the ability to read ohms. What are your opinions on which one in the long run would be better or is this a coin flipper? Great deals on both at FastTech, atm.

Sigelei #19 Tips, tricks, and DON'Ts

Oktyabr — Wed, 22 May 2013 19:40:36 GMT

Hi!

I'm starting this thread because our beloved Sigelei mech thread is growing like an out of control brush fire... posts are buried, posts that should be about a specific model are mashed up with other ones, etc. New posters don't bother to read all 150+ pages so the same questions are getting asked over and over again. Feel free to contribute to this one, if you like!

Vamo over heating issues

EternalblissAE — Wed, 22 May 2013 17:54:34 GMT

I posted this in the New Members forum since I was having issues with my account but that has been taken care of here is a link to my post.

http://www.e-cigarette-forum.com/for...ing-issue.html

Cheers,
Nathan

The Poldiac Fan Club

SilverCloud — Wed, 22 May 2013 15:32:11 GMT

Greetings fellow Poldiac Fans!

I figured I'd start a thread of Poldiac owners to discuss their likes or dislikes about their Poldiacs. :) Right now, I'm vaping a Poldiac UMA with a Kir Fanis Traptank and Kir Fanis telescoping Angel driptip, 18 mg 100% VG DIY peach flavor juice...deeeelightful!

Wish the top cap had some airslots though, not too tank-friendly, IMO....But still hits like a train. Did I hear that Dimitrius is working on some vented top caps?

Vape well,

Bri

IMR Batteries "What exactly does "IMR" mean?"

Joshuasculptor — Wed, 22 May 2013 15:21:17 GMT

Borrowed from: HERE
Battery Guy

What exactly does "IMR" mean?
Greetings Everyone,

I have seen a lot of threads recently on "IMR" lithium-ion cells. DFiorentino and myself have posted some test results recently (seen here and here, respectively). I also have seen a lot of comments recently that indicate a general misconception of what IMR cells actually are, especially with respect to rate capability and safety. The purpose of this thread is to clarify the issues surrounding the "IMR" designation for lithium-ion cells. I will try to keep the techno-jargin to a minimum, but please feel free to ask clarification questions if I lose you.

Unlike most battery chemistries whose name defines the chemistry of the anode and cathode, the term "lithium-ion" refers to an ever growing class of cell chemistries that utilize different materials to host lithium-ions in the charged and discharged state of the cell. Most lithium-ion cells use graphite or hard carbon as the negative electrode host material (typically referred to as the anode), but the selection of the positive electrode material (typically referred to as the cathode) is much more varied. The following three-letter designations for lithium-ion cell denote what cathode material is used in the cell:

ICR = LiCoO2 (also called LCO)
IMR = LiMn2O4 (also called LMO)
IFR = LiFePO4 (also called LFP)

If you take away one thing from this thread, remember this: The term "IMR" simply indicates that LiMn2O4 is a major component of the cathode. It does not necessarily indicate that a cell has exceptional rate capability or improved safety characteristics, properties often incorrectly associated with cells with the IMR designation.

You can stop reading now, but if you want that statement explained, please read on.

The selection of a particular cathode material generally has implications for the performance (capacity, energy density, rate capability, etc...), reliability (cycle life, calendar life) and safety characteristics. The impact of LiMn2O4 on these properties is discussed below.

Performance

The crystal structure of LiMn2O4 has three-dimensional tunnels that enable rapid diffusion of Li+ through LiMn2O4 particles, and therefore lithium-ion cells made with this material can have better theoretical drain rate capability. Conventional lithium-ion cells use LiCoO2 or variations of that material. Cells with LiCoO2 cathodes are typically designated with the term "ICR". The LiCoO2 type materials have a layered crystal structure that only enables 2D diffusion within the layers, so the overall Li+ diffusion rate is slower. Interestingly, LiFePO4, which is commonly used in high rate cells (think A123), has 1D diffusion of Li+ and an overall low diffusion rate. The only way to make LiFePO4 work is to make the particles very small (i.e. "nano") to reduce the distance that Li+ needs to diffuse. "Why not just make LiCoO2 or LiMn2O4 nano size to get even better rate capability?" I hear you ask. The only reason nano LiFePO4 works is that this material has a lower oxidizing potential (which is why the cell voltage is lower) and therefore it does not chemically react with the electrolyte. LiCoO2 and LiMn2O4 actually oxidize the electrolyte slowly with use, so using a nano-particulate cathode with these materials would greatly accelerate aging due to the higher surface area of the cathode, and the cells would have terrible cycle life.

Now back to LiMn2O4. This material has a lower crystalline density and therefore a lower inherent capacity (mAh/ml) than LiCoO2. If you do a direct replacement of LiCoO2 with LiMn2O4, the capacity of the cell will be reduced by ~15%. But here is the interesting thing: simply doing a direct replacement with LiMn2O4 will not significantly increase the rate capability of a cell. In order to get a real increase in rate capability, you need to design a cell with higher electrode surface area and thinner electrodes because Li+ diffusion in the cathode particles is not the only bottleneck to getting current out of the cell. Using thinner electrodes further reduces the capacity of the cell because you will have a higher fraction of "inert" materials like the separator and current collector. This is why IMR cells typically have ~40% lower capacity than their ICR cousins.

Safety and Reliability

An additional property of LiMn2O4 is that it cannot be overcharged. When a "true" (and I will explain why I put that in quotes later) IMR cell is charged beyond ~4.25 V, no additional capacity will go into the cell. The voltage will simply spike. This is exactly the same case for LiFePO4 cells. Cells that use LiCoO2 and its layered-metal oxide cousins can be overcharged, leading to significant safety issues when these cells are charged above their specified voltages. Cells with LiMn2O4 and LiFePO4 cathodes can be damaged by overcharging (oxidation of the electrolyte leads to increased internal resistance, loss of capacity and shorter cycle life), but overcharging to higher voltage does not make them less safe. This inability to overcharge, combined with the lower total energy density, is why lithium-ion cells with LiMn2O4 and LiFePO4 are generally considered to be "safer".

The last property of LiMn2O4 that I will mention is that in its pure form it tends to have very poor cycle life. There has been a tremendous amount of research that has gone into improving the stability of LiMn2O4 to improve the cycle life of IMR cells, and this has produced cells with reasonably good long term performance. However, the easiest way to get great cycle life out of LiMn2O4 is to blend it with a separate cathode material that contains nickel. This includes the layered cathode materials Li(Nix,Cox,Mnx)O2 (aka NCM or 333), Li(NixCoyAlz)O2 (aka NCA) and Li(NixCoy)O2 (aka NCO). I won't bore you with the details, but it turns out that the oxides containing nickel acts to change the local chemistry around the LiMn2O4 particles and helps to improve stability.

The end result is that most cells called "IMR" actually have a significant fraction of nickel-containing layered metal oxide as a co-cathode. This means that these cells can in fact be overcharged, thus minimizing the perceived safety advantage of the cell.

Summary

Not all IMR cells are created equal. One cannot and should not make generalized statements about their performance, reliability or safety characteristics.

I hope this helps dispel some of the mystery surrounding these cells.

Cheers,
BG