no.
Look at the datasheet of an AA alkaline cell with a load of 400mA. The voltage starts dropping immediately and the dimming starts immediately. Their current will be half in 15 minutes and they will be extremely dim in about 2 hours.

A pot by itself must be huge and expensive because it will get hot. Instead, use a cheap little pot that controls a power transistor that gets hot. The transistor is cooled with a cheap heatsink. The transistor needs about 0.8V more voltage from the battery. So you need four AA cells for the LEDs to completely dim in 2 to 3 hours.

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Uncle $crooge

 

bounty, I did a quick search but came up empty. Is there a driver that would allow me do something similar for all 16 leds? Can this use a potentiometer to control the light output? Also I noticed it's for a Li-ion source, would this 16l ed driver need to be rated for 3v that can handle 4.5v max from my 3 AA's? Or are all my questions completely off base.

It probably cost more than I want to spend but I'm interested to know whats possible.

 

hot.Okay audio, so back to 6v, and transistor (w/heatsink), a POT, do I still need the 16 resistors to limit the upper end? How is this configured?

 

Each LED needs to have its own current-limiting resistor unless you buy thousands of LEDs and test them all and match 16 of them to be exactly the same. Then only one current-limiting resistor is needed like in cheap Chinese LED flashlights (they use the resistance of the cheap battery as the single resistor).

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Uncle $crooge

 

Just use multiple switches, and only 14 LEDs and you can control the brightness easily.
One switch would flip on 2 LEDs the other 4, and the third would turn on 8.
Flip only the first one on and you have 2, only the second and you have 4, both first and second you have 6, just the third you have 8, third and first you have 10, third and second you have 12, and all three you have fourteen.
Binary progression, it gives you 8 light settings iwth only three switches and no loss.
If that's confusing let me know and I'll make a simple schematic to clarify.

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The most efficent way to dim LEDs is to use a pulse width modulator, look up SG3524 and other chips in that series. This will dim the LEDs but not drain the battery. If you use a resistor to dim the LEDs you are wasting power as heat and making the circuit less efficent.

 

Or you could use switches to only turn on part of the array and not have to worry about PWM'ing it at all =)

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Audio, is that true I would still need to test every LED even if I know the LEDs I have are the same ones I linked a spec sheet to in a prior post? What is the variable, current? I hooked those LEDs up with 3 new energizer batteries without resistors and it worked great but after being educated that shouldn't work, and I don't want to have the possibility of blowing the LEDs every time I switch out the batteries.

Sceadwian, the issue I have with the switches is that I am using this grid (4x4) as a back light. The light would have hot spots and low spots without all the LEDs lit at the same time. Best case scenario would be being able to dim the LEDs to what is needed, and thus save battery life by only using what is needed.

Alex, I looked up a data sheet for the chip you mentioned and the cost seems reasonable. How is it hooked up and what other components are required?

 

If you need them all on the best + simplest (and cheap) solution for variable power is a 555 timer. The closer the driving voltage is to the LED's voltage the more variable their current use is going to be as the battery discharges and it's voltage sags, this is why constant current sources are used.

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You are going to need a potentiometer to control the duty cycle and a capacitor and resistor for the internal oscillator.

Use pin 14 as the output to the LEDs or use it to drive a larger power transistor depending on your power needs.

Attached Thumbnails

 

 

A555 is far simpler and far cheaper for such a simple application, it also has half the pin count/size

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Sceadwian,can you help me out with the schematic? can a POT be used with the A555?

 

Google is your friend.
LED Dimmer Circuit - Lighting

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The LEDs are probably not 3.6V because their max voltage is 3.6V and their typical voltage is 3.2V.
Their actual voltage might be only 3.0V since the minimum voltage is not spec'd.

Their current must be limited or regulated.

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Uncle $crooge