The ABCs of batteries

[ichaya]

First it looks like there is a great amount of information available here.

Second forgive me for being a newb to Modding.

I see all this info, and my brain starts to melt a little. I swear some of these people have got to be electrical engineers, or something. It's just WAY beyond anything I understand.

Voltage, ok got that, I think everyone is familiar with the diff between 3, and 6 volts. Yeah let's not hook 12 volts onto something designed to be operated at 4 V. You do that - poof flameout 1 atomizer, if you're lucky.
Reverse it and you could be there all day waiting for it to never heat up.


I see all this stuff talking about 'Mah".

Can anyone give me a laymans explaination of this?, and why do we care about those numbers?

[500KV]

I see all this stuff talking about 'Mah".

Can anyone give me a laymans explaination of this?, and why do we care about those numbers?

Google is your friend..

Ampere-hour - Wikipedia, the free encyclopedia

[ichaya]

Thank you I did not actually know that it was called a Amp-hour.

Appreciate it, believe me you try to do a search for 'Mah' ,and you find all kinds of stuff that have nothing to do with batteries.


Short answer, you want a high 'Mah' rating because the measurement means you will have a longer lasting battery.

Did I get that right?

[500KV]

Short answer, you want a high 'Mah' rating because the measurement means you will have a longer lasting battery.

Did I get that right?

That's correct ichaya.

[EldarKinSlayer]

Thank you I did not actually know that it was called a Amp-hour.

Appreciate it, believe me you try to do a search for 'Mah' ,and you find all kinds of stuff that have nothing to do with batteries.


Short answer, you want a high 'Mah' rating because the measurement means you will have a longer lasting battery.

Did I get that right?

mA is how much current the battery will put out

mAh is how long the battery will do it.

[mogur]

A 400 mAh battery will deliver 400 mA for an hour before it goes dead, or 200 mA for two hours. A 200 mAh battery will deliver 200 mA for an hour before it goes dead, or 400 mA for a half hour. See the relationship? It's like the size of a bottle of water. You can pour it out fast or slow, but the bigger the bottle, the longer it lasts at the same discharge rate.

The above isn't exactly true, because a battery isn't exactly like a bottle of water. A battery will last a little longer if you are easy on it. So, a 200 mAh battery will actually produce 20 mA for 10 hours, and that is what the sales department advertises for that battery (20mA*10hours = 200mAh). But if you discharge it at 400 mA, you wont actually get a half hour out of it. The sales department of course, picks a very low discharge rate to measure the amp hours, for bragging rights. If this paragraph is confusing, ignore it, the previous statements are close enough to at least compare the capacity of two different batteries.

[ichaya]

Thank you very much that info about the Mah makes it a bit more clear.


So, what sort of range are we looking at for a good battery for vaping?

I know I'll probably get a bunch of opinions on this one.

I see people building mods that run from 3.7 (ish) volts up to nearly 12.

From what i've read most of the manufacturers are running near the 3.7.

I also have read that anything under 3 just won't work.

[kinabaloo]

A few points.

On first charge: this is normally done at manuafcture, though no harm in doing the first full charge routine to be sure.

I found that chargers do indeed often continue to run (in some way) when they really should switch off and can get very hot (charger and the batteries). It's a nuisance to not just leave it running overnight but at least for some chargers this could be dangerous.

In contrast to the OP, NiMH batteries (AA size) can handle the required current. I use this type of battery and it works well with atomizers.

[mogur]

Thank you very much that info about the Mah makes it a bit more clear.


So, what sort of range are we looking at for a good battery for vaping?

I know I'll probably get a bunch of opinions on this one.

I see people building mods that run from 3.7 (ish) volts up to nearly 12.

From what i've read most of the manufacturers are running near the 3.7.

I also have read that anything under 3 just won't work.

The battery is where modders get to shine. A commercial ecig has to stuff an 8mm dia battery in their 9mm tubes, so they have to deal with about an AAAA sized cell, approximately 180 mAh capacity. It works, and millions are puffing away on them. But, the compromise they make is two fold.

First, you have to charge them frequently, because they are just too small for the job. Moving up to an AAA size roughly doubles your capacity, and an AA quadruples it. A Li-Ion 18650 is the largest commonly available single cell, and it weighs in at about a ten-fold increase in size and capacity.

Second, the commercial ecigs are extremely hard on their Li-Ions because the coils need to draw up to an ampere of current. That kind of current is tough on a 180mAh cell, shortening its life considerably. [Hard on most USB ports, as well.] A modder's cell of 750 mAh AA size (14500) can puke out 1 amp at intermittent intervals and barely compromise its maximum life.

So the cell you want is whatever you are happy carrying around. Like kina says, even lower energy-density NiMHs work fine, given that you use at least three of them, to boost their individual cell voltage of 1.2 v up to 'vaping voltage'.

The voltages are all over the place in modders forums, because coils vary so much in resistance, and atomizers in design. I've seen commercial coils at 4.5 ohms, and I just disassembled a DX cigar with a 1.2 ohm coil. It would take almost four times the voltage to heat a 4.5 ohm coil to the same temperature as a 1.2 ohm coil. The reason is that current determines the temperature of the coil, and it takes four times the voltage to push an amp of current through a 4.8 ohm wire as it does through a 1.2 ohm wire.

Commercial ecigs use microchips, some of which drive power switchers that can alter the voltage and current delivered, so you can't always strip the autoswitch and pcb out of a commercial, replace it with a push button, and always get the exact same performance out of the same atomizer and battery. A good rule of thumb is to measure the coil resistance, calculate what voltage will give you about an amp of current at the cell's peak voltage, and let the current fall off with the battery voltage as it's depleted.

Most Li-Ions have a nominal voltage of 3.7, with a peak voltage of 4.2, and cut-off at 3 volts. But a commercial ecig usually stops vaping properly at about 3.5 volts anyway, and their micro disables the cell at ~3.3 volts. So, for an example, if you used two Li-Ions in series, you would have a working range from 7.8 volts down to 6 volts, with a brief, fully charged voltage of 8.4. That is way too high for most atomizers, so you have to buck the current down to 5 volts or so, or whatever makes your coil and you happy.

[ozrick]

Anyone else find that reading posts with Every First Letter Capitalized makes for an interesting read. For me it's like an accent on each word and gives me motion sickness!

<3 cell.