Charging stock e-cigs...the good, the bad, the ugly

[AttyPops]

OK, so I need to double check something with the techs here. I know some have built charging circuits (for some reason, but hey, to each their own).

So for stock e-cigs, say a 510 super-mini either 180 or 280, or for the standard eGo batteries, basically any 510 battery connector:

The current limited resistance is a function of the charger and not the battery????????

I say this because, supposedly, "everyone knows" that you can't charge a standard 510 super-mini with an eGo charger because "it will overload it".

Since the voltages are the same, I'm assuming that the battery gets fed too many amps..because the current limiting function is a function of the charger and not the e-cig battery/power supply itself (discounting battery internal resistance). And if it is fed too much it gets too hot too fast.

If the charger (rated at output of 4.2 volts and 480 mA) were simply applying the power (and charging logic)...and the e-cig limited the current, it could only draw a MAXIMUM of 480 but would in reality only draw what it needed. So I don't understand why an eGo charger would blow up a super-mini since amps are a function of the load's draw. MAX amps are an attribute of the charger.

The only way it would mess up would be if they made the e-cig stupid and built the current limiting into the charger. Doesn't really make much sense to me, but I don't build/design chargers. I know there's limits somewhere.

So....do eGo chargers "overload" the super-mini's or is that a wives' tale? The charging function must be more-or-less a direct wire to the battery then, yes?

-or-

Is the charger rating a "max amps" rating? That would have made more sense in the design...having the battery limit the charge current with a current limiting resistor.

And P.S.
Just to be clear...I am talking about the charger not a wall-wart A/C to USB transformer.
I've always given the advice of "use the proper charger for the e-cig...the one that comes with it/designed for it"...but I'm wondering about the internal design, mostly of the "battery" unit.

 

[asdaq]

The batteries are dumb in this case, and the amperage is too great from the charger. The charger itself monitors the battery voltage to determine when to cut off.

Sent from my Nexus 4 using Tapatalk

 

[AttyPops]

VOLTAGE....sure. That's expected of a charger.

It's the amps that throw me. In all other device designs, the device determines "the load". That's why you can plug a 1500 watt space heater into your wall outlet and also a 1 watt little gizmo....the device determines the amp draw.

If the e-cig doesn't limit the incoming charge current....that's dumb, IMHO.

I understand when there's a problem due to reversed polarity or battery failure or crappy charger that over charges. But I don't understand why it wouldn't have a current-limiting resistor on the battery to limit amps. But maybe that's how chargers are...I've never designed or built one. People here have though.

 

[asdaq]

That's just it. To design a cig looking e-cig, choices were made to only add the smallest of components and leave the charging circuit in the charger for space considerations. This is essentially how I build mods too, I haven't that much desire to carry around a charging board all the time just for that benefit.

And you are right, a smarter device determines the load of the draw, and even a space heater has more to it than a coil and switch. If it wants to be UL listed it does at least. As for matching chargers to devices/ batteries, the mAh capacity should be higher than the charger's delivery rating of mA. That said, I am guilty of charging AW 14500's (600mAh) on a 650mA charger, but they are LiMn, so a wee bit safer.

 

[WarHawk-AVG]

OK, so I need to double check something with the techs here. I know some have built charging circuits (for some reason, but hey, to each their own).

So for stock e-cigs, say a 510 super-mini either 180 or 280, or for the standard eGo batteries, basically any 510 battery connector:

The current limited resistance is a function of the charger and not the battery????????

I say this because, supposedly, "everyone knows" that you can't charge a standard 510 super-mini with an eGo charger because "it will overload it".

Since the voltages are the same, I'm assuming that the battery gets fed too many amps..because the current limiting function is a function of the charger and not the e-cig battery/power supply itself (discounting battery internal resistance). And if it is fed too much it gets too hot too fast.

If the charger (rated at output of 4.2 volts and 480 mA) were simply applying the power (and charging logic)...and the e-cig limited the current, it could only draw a MAXIMUM of 480 but would in reality only draw what it needed. So I don't understand why an eGo charger would blow up a super-mini since amps are a function of the load's draw. MAX amps are an attribute of the charger.

The only way it would mess up would be if they made the e-cig stupid and built the current limiting into the charger. Doesn't really make much sense to me, but I don't build/design chargers. I know there's limits somewhere.

So....do eGo chargers "overload" the super-mini's or is that a wives' tale? The charging function must be more-or-less a direct wire to the battery then, yes?

-or-

Is the charger rating a "max amps" rating? That would have made more sense in the design...having the battery limit the charge current with a current limiting resistor.

And P.S.
Just to be clear...I am talking about the charger not a wall-wart A/C to USB transformer.
I've always given the advice of "use the proper charger for the e-cig...the one that comes with it/designed for it"...but I'm wondering about the internal design, mostly of the "battery" unit.

Li Ion need CC/CV, most of the chargers especially those small ones the current is set by pin 2 on the RProg
Based upon the TP4056 chip
http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Prototyping/TP4056.pdf

Rprog Current Setting
RPROG(k):IBAT(mA)
10: 130
5: 250
4: 300
3: 400
2: 580
1.66: 690
1.5: 780
1.33: 900
1.2: 1000

See that surface mounted resistor and trace on pin 2 (the 122)
from the PDF above if you changed that resistance you change the MAX CC output of the IC

http://www.instructables.com/id/Reading-Surface-Mount-Resistor-codes/
1st value-2nd value-multiplier
3 9 1 = 390 ohm resistor
2 7 0 = 27 ohm resistor
2 3 3 = 23000 ohm or 23K ohm resistor

There are some resistors which have 4 digits. The formula is the same with the addition to a digit.
1st value-2nd value-third value-multiplier
2 3 5 3 = 235K ohm resistor

You CAN overdrive a Li Ion battery (shove too much current in too fast overheating the battery [heat+sealed Li Ion = pressure, pressure = bad bad in a Li Ion]...based upon the "C" rating
http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries

Borrowed from a RC forum

The 'C' rating of a battery or battery pack is equal to the capacity to supply power for one hour. This is measured in Amperes or Amps. For example. your 4400 mA pack has a C rating of 4400 mA. Often the term 'C' is discussed as a measure of how much current can be drawn or charged back into a battery. For example the new crop of Lipo cells can have a current rating of 20C which means you can safely draw 20 times the capacity from the cell. In other words if you have a 1000 mA battery with a 20C rating you can draw 20 Amps (20,000 mA) from it. You may also see specifications stating a charge rate for a cell of 2C. Using the same 1000 mA battery as an example that would mean you can charge the battery at 2000 mA safely.

IR is the rating of a cell's internal resisance and is measured in Ohms.

Slower charging is always better with Li Ion, less heat is generated

Hope that helps

 

[AttyPops]

Yeah it does. Battery University helped too.

Basically, since the charger's output current depends on the mAh rating (well, C rating) of the battery...and there's no easy way for the charger to tell what battery is attached, a 450 mA charger outputs too much current for a super-mini 180 mAh battery...because it thinks there's a ?450 mAh? or higher battery attached but there isn't.

They should develop a color code, or some markings, or maybe min battery mAh rating on the charger.... (I suppose the charger output mA IS kind of a code...if you know how to interpret it.)
Because it's up to the user to match it up properly.

A current limiting resistor may not work because the charger needs to vary the current for the battery. Besides, it would cause a voltage drop. IDK. Maybe they will get it miniaturized enough to build it into the battery and avoid problems.

Anyway, thanks for the replies folks.