Basic circuitry questions.

[FrostyDream]

So I want to make a couple of sketchy mods out of things in my house. I have a few questions before i get started... Can I use some old phone batteries? I have some batteries all 3.7v with anywhere from 800mah to 1400mah and was wondering if there is really anything different about them and if you could charge them with just the negative and positive connections. Also, is there a way to put LED's in while maintaining the same voltage output? Maybe with resistors or something? Lastly and most importantly, how do I wire it so I can use a charger without taking the battery out? If i wired it with negative from battery>switch>positive of 510 connection>negative of 510 to positive of battery, you would have to hold the button down for it to charge... If you could look at the picture you will see what I was thinking as a fix for the charge... Any help is appreciated, thanks.

 

[LucentShadow]

So I want to make a couple of sketchy mods out of things in my house. I have a few questions before i get started... Can I use some old phone batteries? I have some batteries all 3.7v with anywhere from 800mah to 1400mah and was wondering if there is really anything different about them and if you could charge them with just the negative and positive connections. Also, is there a way to put LED's in while maintaining the same voltage output? Maybe with resistors or something? Lastly and most importantly, how do I wire it so I can use a charger without taking the battery out? If i wired it with negative from battery>switch>positive of 510 connection>negative of 510 to positive of battery, you would have to hold the button down for it to charge... If you could look at the picture you will see what I was thinking as a fix for the charge... Any help is appreciated, thanks. View attachment 259128

Hi. I don't know much about old phone batteries, but I'd guess that they would be meant for far lower current draw than what typical e-cig use needs. I'd suggest looking up any model numbers to find specifications for maximum output current, and make sure that it's higher than what your atomizer resistance will demand from the battery. Ohm's law works for that.

You can put an LED, with a current-limiting resistor in series with it, on a parallel circuit between the 'firing' switch and the atty connector. There are calculators online that can help determine the correct resistor value, or you can experiment, if you have some spares. Using a parallel circuit keeps the output voltage intact.

I don't quite understand what your intent is for charging it. If it's to use an eGo charger, I would not offer any advice, other than it sounds like a bad idea, since eGos have a PCB in them that this would not have, and that may be important.

If you buy a charger PCB to install into it, then that should have it's own instructions for proper use. I would personally avoid them, but some here have used them, and you can probably find some info here about them. I know Evolvapor sells a charger PCB, and others can be found online, I'm sure.

The diagram that you show is wired a bit backwards, and the toggle switch is ill-advised. You'd normally wire like so:

conn- > batt- and batt+ (> optional slide switch) > switch > conn+

Wired as pictured, you are putting the positive battery potential on the chassis of the unit, which is generally inadvisable in electronics. The toggle switch allows for accidental always-on state, which is also inadvisable in an application such as this. Most would prefer a slide switch, or a toggle that's not easy to activate, wired in series with the firing switch as a safeguard against 'pocket firing'.

 

[Rocketman]

Frosty,
I think it's great that you want to make your own mods. Search around the modding forum and battery mods sub forum.
The craze now is digital display variable watt APVs but plain old DIY 3.7 volt mods still make plenty of people happy (myself included).

To answer some of your "Basic circuitry Questions" I suggest reading up on;
a) Lithium batteries,
b) Light Emitting Diodes and their operating parameters (voltage drop and current limits),
c) A little bit of 'ohms laws' for simple DC circuits.
d) current path tracing (series and parallel paths).

While you can follow picture tutorials you will get more satisfaction from understanding the design principles and vaping your own DIY device.
After you have a basic understanding of the electrical properties of the components you plan to use, then comes the mechanical "how do I make this fit" artistic portion of DIY. The eGo charger is fine. I use many of them to charge DIY mods either with a second 510 connector for charging or 'vape while charging'. I also use rubber bands/hair ties to hold buttons down while charging with the 450/500ma eGo charger. Be prepared for a long wait if you do this to charge parallel 2600mah 18650 cells
The ones in this picture either charge from a bottom 510 port or with the bubber rand trick to hold the button down

 

[FrostyDream]

I have a 510 charger with no pcb, just the 510 connection wired to usb. Maybe I should put a charging port on the side with mini usb? I have the materials, I just don't know how. The toggle switch is because if it wasn't there I would have to hold the button for it to charge. If i had an LED in there, that creates another problem... keeping the power away from the led. Since charging takes a higher voltage, wouldn't the light blow out? I guess the resistors would fix that, but then wouldn't they keep the battery from getting enough power to charge? How do I know the current when all it gives me is mAh and voltage?

 

[FrostyDream]

Are those yours, or did you get that from a google search?

 

[Rocketman]

I have a 510 charger with no pcb, just the 510 connection wired to usb.
That is a "charger" from a disposable. It is not safe to charge anything else with it. 5 volts straight from the USB will destroy a Li-ion cell. It's a nice source for a connector though.
The 'Smarts' were located in the disposable e-cig.

If i had an LED in there, that creates another problem... keeping the power away from the led.
The LED might draw current and mess up the CC/CV charging profile (confuse the charger). If you kept LED current to 1 or 2 ma then it would be OK.

Since charging takes a higher voltage, wouldn't the light blow out?
Charging voltage doesn't go above the max voltage for the cell. The cell sucks up charging energy because it is at a lower voltage then slows as voltage rises. Typically 4.2 volts.

I guess the resistors would fix that, but then wouldn't they keep the battery from getting enough power to charge?
Resistor would only be in the LED path. Not in the charging or vaping path.

How do I know the current when all it gives me is mAh and voltage?
Charging rates are normally between 0.2C and 1C (pretty hot). C is the mah. Charging a 1000mah cell with 500ma is charging at 0.5C

Yes, those are mine.

 

[cadcoke5]

Here is a very basic manual e-cig connection diagram, with a LED. Note that you must have the correct LED value there, or the LED may burn out immediately.



This basic circuit does not have any provision for charging. The battery would need to be removed for that. I suppose that some other sort of main power switch, such as a double-throw type, could be used to re-direct the power to the charger. Here is a modification to the circuit, for the main power switch to have 3-positions; On-Off-Charge. These kinds of switches are abbreviated SPDT [Single pole, double throw]. Note that all the switches must be rated for the current the atomizer needs.


-Joe Dunfee