Enough with the darn flashlight already..
Its junk and clearly lowest cost was your only motivation for its "design"... You stated yourself (in numerous other posts about this silly flashlight) that you need to replace LEDs on a yearly basis because they have burnt out...

 

In my flashlight I have three primary AA cells and a PWM controller.
As for the charging, I am not entirely sure which battery packs are you talking about, but any lithium based battery charger will have balancing which basically substitutes parallel charging. I haven´t seen any NiCd or NiMH packs for a long time so not sure how it was done with those.

Not seen them?...well they are still in use over a broad range, since they are more stable and can be fast charged, which is a bad idea with lipo and li-ion... But the use of batteries is offcourse never a good choice with real electronics, with small currents and volts....they are way too unstable and noisyyyy.... Though sold for huge prices for hifi turntables as 'perfect powersupply'.... !000dollars or 1500... It's allways fun to see the different kind of batteries loading on the fastcharger of rc electric stuff and perfect to generate you ipad or something.which has a shitty loadunit.pffff cheap smps thingy.....referring to the asuswallmart thing i got with it. And then looking at the beatifull waves on the fastloader..with the best accu...a load one....kind of ironic...

 

.......................
A dumb engineer would conclude that you have to use a resistor to limit current to an led;
A smart engineer would conclude that the essence here is to limit current to an led, however you achieve that is application specific. ie in some cases you may have to use a resistor and in other cases it is entirely OK to NOT use a resistor.
..................

And a smarter engineer would conclude that you can also use a constant-current circuit or a current-output switching regulator to control the LED current.

 

Not seen them?...well they are still in use over a broad range, since they are more stable and can be fast charged, which is a bad idea with lipo and li-ion... But the use of batteries is offcourse never a good choice with real electronics, with small currents and volts....they are way too unstable and noisyyyy.... Though sold for huge prices for hifi turntables as 'perfect powersupply'.... !000dollars or 1500... It's allways fun to see the different kind of batteries loading on the fastcharger of rc electric stuff and perfect to generate you ipad or something.which has a shitty loadunit.pffff cheap smps thingy.....referring to the asuswallmart thing i got with it. And then looking at the beatifull waves on the fastloader..with the best accu...a load one....kind of ironic...

???? Most of what you are saying is gibberish.
Please post in idiomatic English.

 

In my flashlight I have three primary AA cells and a PWM controller.
As for the charging, I am not entirely sure which battery packs are you talking about, but any lithium based battery charger will have balancing which basically substitutes parallel charging. I haven´t seen any NiCd or NiMH packs for a long time so not sure how it was done with those.

Ah, good for you on your flashlight.
Are you trying to say you have never seen a battery pack? What do you think is in your car but six cells in series? You have never seen a 9-volt battery? R/C cars? do you have a wireless home phone?

 

And a smarter engineer would conclude that you can also use a constant-current circuit or a current-output switching regulator to control the LED current.

And those are, in deed, superior designs. Yes, good engineering is preferable. It just isn't the only option available.

 

And a smarter engineer would conclude...

if an engineer needs to "conclude" that, s/he cannot be too smart: s/he should just know it.

 

I think the only time you can power an LED directly from a battery without a current limit circuit of some sort, is when using a small button or coin cell that has a high internal resistance.
Try doing that with low resistance batteries such as AA or AAA alkalines or NiMHs and you will likely fry the LED.

Re: "Try doing that with low resistance batteries such as AA or AAA alkalines or NiMHs and you will likely fry the LED"

Try it sometime. I must have a dozen flashlights with AA and AAA batteries around the house. Just batteries and white LEDs. No PWM circuits. Not even resistors.

 

I'd like an example of that.

Dannyf does not imply that a good engineer does not read the data sheet, but understands it and the part, and knows what s/he can do outside the data sheet specs.

 

Ah, good for you on your flashlight.
Are you trying to say you have never seen a battery pack? What do you think is in your car but six cells in series? You have never seen a 9-volt battery? R/C cars? do you have a wireless home phone?

No, I meant which kind of battery chemistry you mean. Each chemistry has its own quirks, and some like the lead-acid you mentioned can be very happily charged in series even in very large series strings.

 

which kind of battery chemistry

Carbon-zinc, alkaline, NiMH, NiCad ... AA and AAA. Did you think 9 V batteries were just one cell? Am I out of touch? Do people use 9 V batteries any more? Do home phones use Li-ion?

 

if an engineer needs to "conclude" that, s/he cannot be too smart: s/he should just know it.

A good Engineer doesn't know everything.. But is "smart" enough to know where to find the proper information/answer..

 

Carbon-zinc, alkaline, NiMH, NiCad ... AA and AAA. Did you think 9 V batteries were just one cell? Am I out of touch? Do people use 9 V batteries any more? Do home phones use Li-ion?

Ok lets sort this mess out. AA or AAA has nothing to do with anything. Carbon-zinc and alkaline are non-recharchable. I haven´t seen a recharchable 9V in at least fifteen years and have no idea if anyone still seels them... Which leaves out with NiMH and NiCad, to which I have to admit I have not a lot of knowledge about charging in packs, but hey everyone does it so why not.

I am not sure where you got lost, but I was initially talking about your claim that

Good theory suggests not charging batteries in series, but every rechargeable battery pack does so.

to which I replied that definitely not every battery pack does so (see Li-ion packs), and that there are batteries that absoultely don´t require said practice of not charging in series (see lead acid). Frankly I don´t know what we´re still debating.

 

Ok lets sort this mess out. AA or AAA has nothing to do with anything. Carbon-zinc and alkaline are non-recharchable. I haven´t seen a recharchable 9V in at least fifteen years and have no idea if anyone still seels them... Which leaves out with NiMH and NiCad, to which I have to admit I have not a lot of knowledge about charging in packs, but hey everyone does it so why not.

I am not sure where you got lost, but I was initially talking about your claim that to which I replied that definitely not every battery pack does so (see Li-ion packs), and that there are batteries that absoultely don´t require said practice of not charging in series (see lead acid). Frankly I don´t know what we´re still debating.

Maybe we both need to get out more. You have never seen a rechargeable alkaline battery or a 9 V? Do R/C cars still use NiMH battery packs? What is in your home phone?

 

if an engineer needs to "conclude" that, s/he cannot be too smart: s/he should just know it.

I'm smart enough what the word conclude means.
Do you?

 

Re: "Try doing that with low resistance batteries such as AA or AAA alkalines or NiMHs and you will likely fry the LED"

Try it sometime. I must have a dozen flashlights with AA and AAA batteries around the house. Just batteries and white LEDs. No PWM circuits. Not even resistors.

And you've taken them apart and examined the circuitry?

 

And you've taken them apart and examined the circuitry?

Have I taken then apart? Yes. I confess I found one LED lamp at Dollar Tree, shaped like a regular light bulb, that actually had a resistor. Most have nothing.