The ABCs of batteries

[kinabaloo]

Personally, I think 3.7v is just fine - so long as the battery is of a suitable size, as this not only lasts longer but is able to put out more current (lower internal resistance); the difference is quite remarkable. Once you have a decent 3.7v battery, you won't seek a higher voltage IMO.

[a2dcovert]

I just find it hard to believe that this myth about battery charging is continuing. mogur is right about the charging of protected Li-Ion batteries. The protection circuit is designed to protect the battery from over charging, trickle charging, and excessive discharging. I don't care what the manufacturer says about charging the batteries, it does not apply to Li-Ion batteries. Once the light on the charger turns green the charging circuit is terminated, period. You can leave the battery on the charger till hell freezes over and it wont charge the battery any more than it is after the circuit terminates. Leaving the battery on charge any aditional time is just a waste of time. But, if you wiah to still follow the manufactures instructions then by all means do so. it wont hurt because the protection circuit will protect the battery from all of the above conditions.

You can do what you wish because there is no way you can harm these protected batteries with the battery charger. The protection circuit will always protect the batteries from abuse. So waste your time if you wish to, it wont hurt.

Kevin

[four2109]

This is a great sticky, but when I went to reference it, the charts are gone.

Can we get those back? Then I'll make my own copies
Thanks

[vapordad]

[quote=Cellmeister;318921]Sorry But This Is Wrong: Maybe Thats Why No One Asked You.

I don't know either cellmeister or mogur.

Cellmeister,

I have to say that the first 5 words on here, followed by the next 7 in your first response to mogur are quite frankly, ****!

If, in fact, you want to protect the rest of us with your advice in the rest of the post, you might try being a bit nicer. I also think that mogur was pretty good about his first couple of rebuttals, but don't blame him for getting snippy when you repeatedly criticized him.

Further, he sounds like he has done more research on the subject, and quotes outside sources, unlike you who keeps just repeating that he's wrong.

Get a Flippin' life, Cellmeister. It is posts like yours, in otherwise helpful threads, that make me enjoy the other e-cig forums better. Grow up.

Mogur, thanks for assisting the rest of us and imparting a little knowledge in spite of some jackass with a chip on his shoulder.

Cellmeister. Take this how you like, but your attack reminds me of the shock and awe attack of 2003--unprovoked.

[joedirt]

There really isn't "good" LiIon batteries and better one. There are some mislabeled especially the 18650's which might lie about the 2400mAh. (Unless you are talking about the different Lithium mixes being used like Cobalt, etc.. But for the cheapy batteries they are all the same, and you only need to compare the mAh)

You have to decide how much current you want which sets the heat. This is also probably related to how much air you suck past the heater as well, or how "wet" the coil part gets.

So, say you have a 1" coil and it is 3ohms. And you have another coil from different atty that is 1/2" and comes in at 1.5ohms (same NiCr wire). The heat the coil gets up to is based on the current for both. 1A should be some temp, however in terms of heat generated, it is I^2*R so the larger coil has more heater area and more resistance so twice the heat is applied to the air (a 3W heater instead of 1.5W heater)

Now if you apply a fixed voltage, like 3.7V to both, this sort of compensates, but the temp of the coil is different. For a fixed voltage case, the 3ohm coil, it is 1.2A and 4.6Watts. For the 1.5ohm coil, it is 2.5A and 9.1W. Power for a fixed battery voltage is V^2/R so twice the resistance half the heat. However, in this case the smaller coil gets much hotter with 2.5A and might burn more, it might also vaporize a lot more because of extra convection and radiation (which I'll have to look, but might be proportional to temp squared).

The reason the battery rating matters is besides the longer usage on a charge, as a rule of thumb for LiIon batteries can discharge safely "1C" so a 2200mAh shouldn't exceed 2.2amps or you are reducing the battery life. Though, for this application it is very short bursts over a long period of time.

This is partly why I suspect the stock AAAA size batteries don't live up to 200 charges.. because the smaller capacity 3.7V batteries can't handle the 1000mA or so.

Battery University The high-power lithium-ion
batteryuniversity.com/partone-5A .htm


---------------------------------
My current ideal solution is to take two heater coils in one atty and then use one 3.7V battery and the size of it depends on how long between recharges. I also think using a L200C voltage regulator with adjustable current control would be the simplest solution

Also make sure you use the protected LiIon. In fact for the people using the 7.4V stack of two, they sell voltage protection mini PCB for those applications for like $1-$2 and it will keep the batteries charging better. Un-protected ones could be really bad in your pocket.

[kinabaloo]

The reason the battery rating matters is besides the longer usage on a charge, as a rule of thumb for LiIon batteries can discharge safely "1C" so a 2200mAh shouldn't exceed 2.2amps or you are reducing the battery life. Though, for this application it is very short bursts over a long period of time.

This is partly why I suspect the stock AAAA size batteries don't live up to 200 charges.. because the smaller capacity 3.7V batteries can't handle the 1000mA or so.

A good point - higher capacity batteries not only last longer between charges (obvious) but will also probably do more recharges (especially in high current drain application such as the e-cig). So their overall lifetime will be far greater, years rather than months.

[joedirt]

A good point - higher capacity batteries not only last longer between charges (obvious) but will also probably do more recharges (especially in high current drain application such as the e-cig). So their overall lifetime will be far greater, years rather than months.

You can look at some of the google stuff for lithium ion. I think most 3.7V are lifetime of 300 full charge/discharge cycles. But YMMV as there are Cobalt, LiFePO4, Manganese Oxide, etc. versions of LiIon

There are some newer MnO LiIon mixes like the ones used for powertools. You'll notice they are only like 1100mAh but they can put out 5C or 10C discharge rates (so like 15Amps!!). Basically, if you are using more then 1C bump down the effective mAh capacity by like 10%. I can't see these new cells being useful for the same size.


There are like 20 mfgs of "cells" so these are all what you buy as a "18650" (most likely the chinese vendor)

Newer MnO cells
Sanyo UR18650W 1600mAh - 700 cycles until 75% initial capacity
Sony 18650VT 1000mAh - 500 cycles until 90% capacity (2A discharges)
Saphion IFR28650p 1100mAh - 600 cycles until 70% capacity (10A)


Maybe we can get a list of common cells that show up as the 2400mAh chinese ones.


I would say this..
If you had a 16340 with 3.6V 800mAh. Not only is a 2400mAh battery going to last almost three times as long on a charge, but if your discharge rate is too high (like drawing 1A or more), then your battery will die prematurely. Especially if we are talking about a 3V 700mAh CR123.

Also one quick comment a USB passthrough hooked to a computer will only allow 5V and 500mA (it is current limited even though a large 5V battery would be doing 1700mA).


From here source academic paper.
http://www.electrochem.org/dl/ma/202/pdfs/0209.PDF

[joedirt]

Also, store not-used batteries with like 40% charge on them. They will drop over time so charge them back up to 40% like once a month. (or charge to 100% and use them for a little bit).

There is no "memory" effects on Lithium Ions. There is no need to totally discharge first and then recharge. This applies to regular old protected LiIons you bought as a rechargeable battery.

****NOTE: this may not be true with the sealed smart batteries and the microcontrollers that blink when low or used too often. Also they appear to have a cleaning cycle on some, so follow directions on these.

Never charge a really cold battery and probably not a really hot one. It effects the chemistry inside and you lose some capacity.

[four2109]

You are way over my head. I just have a simple question about the 18650's at DX. They seem to be less expensive for more mAh.
exp:
$8.18 for 2500 mAh (blue) vs. $8.79 for 2000 mAh (grey)
Is there any difference between the blue and grey? Reason for the pricing? What am I missing?
Thanks

[Sun Vaporer]

You are way over my head. I just have a simple question about the 18650's at DX. They seem to be less expensive for more mAh.
exp:
$8.18 for 2500 mAh (blue) vs. $8.79 for 2000 mAh (grey)
Is there any difference between the blue and grey? Reason for the pricing? What am I missing?
Thanks

42--Yes--a big difference--the grey ones are protected batteries (Short circuit, over-charge and discharge protection) as opposed to the blue which are not---protected is the way to go for saftey as you do not what them to blow up on you.

Sun