once you go DD (or resistered as it would be) you will never go back
of course like harry said, its all about HOW you do any of it. and your intended USE too.
i will tell of the secret Advantages of DD, in a
Biased sort of way. somone else can debate the other side effectivly too.
If you have a great battery, that is not being driven to hard for what your using it for, like li-ion or ni-?? things which hold thier voltage well WHEN used at normal discharge rates.
1] sure it declines, lots even, but when it declines due to the lack of battery, many other things happen too.
A) Runtime:
The led is in its more efficient state then, you have less battery capacity, but now your not pulling as much juice from it either, so it keeps going, as it gets down further less output, and less current draw, the battery becomes more capable of capacity at lower rates, and it STILL keeps going . . . etc etc, its the never ending story.
B) Battery treatment:
The battery doesnt get pulled down hard, when it is having the hardest time keeping up. A proper driver will assault the battery with current draws , when the battery is least capable of outputting voltage. batteries like being treated nicer
exploding batteries and leaking batteries are not fun things.
C) Perfect matches:
In the correct configuration an unprotected li-ion can potentially be used , because at some point, in the never ending story, the led gates will no longer trigger, the led will output no light, and draw no current. with a driver the unprotected battery can be destroyed from overdischarge , and you wont even see it comming.
D) Built in battery meter:
You will know WHEN the battery in your light is charged, and when it Needs a charge, and you dont need to look anywhere, or have an indicator to show you that, by the time your disgusted with the ouptut, its time to charge, BUT it doesnt shut off completly.
Your family might not stuff some battery in it backwards trying to get it to work, when nothing comes out. here the consumers will grab a DD light, and as long as it is running they will just USE it, even if i noticed it needed charging.
If the battery is not charged due to some charger problem, you will know it right away, not when its to late.
E) Human Eye Compatable:
by the time the light declines to these lower levels, if you were actually USING the light in the dark, not showing it off, or trying to impress, your eyes have adjusted to the dark, and the lack of output is not so big an issue. power outages or going to the boondies, the auto adjusting of the human iris , works in tandem with the decreasing output
until you start seeing the Banjo player, without any light at all
F) HEAT reduction:
during long runtimes the decline also reduces the drive and therefore heat to the led, because leds last longer when not heated so badly, the DD has the advantage of the heat declining too. with a proper driver, the heat can continue upward on a long run of the light, with DD total power is decreasing , so to is the ammount of heat. this is also true for the battery heat, which gets higher near the end of discharge. all of the items battery, led , including the resister, have less heat outputing the longer it runs. depending on how well the total package dissipates heat, the DD has the advantage of reduced heat for long runs, furthering longevity of the led and battery.
G) Overdrive:
you can always charge it, and overdrive harshly at a full charge, to impress others
MANY drivers overdrive to a FULL direct drive anyfriggenways at certian matched led/battery voltages. so mabey we should worry more about that, than the SAME overdrive occuring in resistered lights. with resistered you could prevent ALL overdriving of the led, UNLIKE some of the driver boards and li-ion voltages
or you can overdrive like crasy, which lots of drivers wont even do.
2] its pure simplicity, done right not much CAN go wrong, wheras the driver board, done wrong or even some that were Sold, you end up with a Carbonised Mosfet, and Nothing, no way to fix it, no way to get light. poof nothing. try and solder the hair width legs on a microchip, with a swiss army knife magnifying glass and the sun, 20 miles from civilisation.
3] some drivers suck juice when Off, DD and resistered, usually use full disconnecting switch methods. (adding full disconnect to drivers that use power is good idea) what good is a light that depleated a battery before you turned it on.
4] with some simple math and the right battery and 2 parts from the local store, almost anybody can make the curcuit. and lights that DD are usually sub $30 costs after the tripplet markups. almost anybody can figure out what is wrong with it if something fails too, it doesnt take a PHD to make or repair one.
5] calculated out , most of my DD or resistered lights are MORE efficient than than my driver lights, assuming the friggen battery isnt dead in the driver light :sick2: all of my DD lights will run longer than the driver lights , even when set to low, but that is just because the driver lights i have dont go low enough.
6] DD works best with either ENOUGH battery , like say 3 fat alkaline D cells, or Rechargables, and rechargables are pure pleasure of using a device whenever you want , Drivers have more issues and problems when they are Designed FOR alkalines, and dont handle rechargables well (especially li-ion). because you have to have enough power to begin with (to maintain voltage), you have runtime when needed. a driver does not make up for the lack of battery, DD prefers to have some battery to begin with.
7] in an emergency, what would you rather have happen? light gets dimmer , and stays running, or its nice and bright, everything is peachy keen , then your in complete darkness. and yes this even happens when in LOW levels with drivers.
8] with Drivers you need to carry a spare , cause you just never know, even at low, when functions will ceace, with DD you can squeezze out some sort of light for sooo much longer after the other light would have died. so generally i dont carry or need a spare for the DD light, with driver lights one is wise to carry a spare or a charger or something. with the DD, you will know long before it dies, that you need to conserve.
9] some light battery driver combinations are being regulated by the Lack of battery ability, an alkaline has a very poor Constant current discharge curve for example, a great current driver makes that even Worse. With DD the poor alklaine doesnt "Have To" keep up with the driver, only with its own inability to output current at that voltage, so without driver losses, the alklakine will self regulate, and less need to be "rested" between uses, when it cant put out the power, it just Doesnt
simple as that. so an alkaline which is really a bad choice for DD, still makes out from DD when it drops in output. with constant current driver for the led, the battery actually gets an INCREASING current draw, much worse than the graph showing constant current discharge of the battery.
10] certian battery led combinations are a beech, require a buck&boost driver, not just a buck or just a boost driver, the drivers are trying to do unnessiary things, when the voltages are as practically matched at you can get with nothing. Leds are not like Incan bulbs, where they draw almost as much current , when they put out little light. Matching voltage to bulb item WAS good enough for incans, why not leds. Leds are Voltage Critical, but then so was the incan, unless you liked yellowish glows that took almost as much power.
11] drivers HAVE resistors
and the lights have resistance, and so there already is resistance at play, and causing losses, some drivers even have large voltage drops on diodes that waste power, and mosfets, not fully triggered , and when transistioning between switching are still resistors. Check that driver efficency when the battery voltage is low, it might not be as wondefull as testing it when there is sufficinet voltage.
12] that argument that PWM isnt efficent, probably the least of the issues in flashlights
resisters use current control (so to speak) no PWM, and there is no strobing seen ever.
13] initially (long ago) drivers were not very well worked out, they had no cutoff for battery, they had no levels, they had no indicators, they were terribly inefficient, they were not very available, they got Hot, they never fit in things correct, and they cost a lot. nowdays drivers are available that dont have so many problems, to bad that isnt what is going into lights
14] you MUST design the DD light to use a specific battery type voltage, drivers are More capable of transversing voltages, but most of them dont really do this well anyway, with the DD, your making for ONE battery type only, and for efficency the matching of the battery and led is nessisary, without it, efficency will go to heck fast. like if you try and match 2xcr123 cells to a single white led using resitors, you might as well get a driver.
15] batteries in Seires with DD systems it is less likly that a battery will be reverse charged, the voltage differential between the led operating and not is so small (the disadvantage) that when a Cell in a series set becomes completly depeleated current consumption drops hugely, and the cell will not get reverse charged. no reverse charge, no ruined leaking or poping battery. drivers will drive a series set of batteries right into the ground. all of this completly dependant on the driver or matching of course.
