4.8V in 3.6V 1 watt safe?

Title says it all... basically, I would like to know if it is safe to run your generic, cheap 1 watt LED light (Dorcy Metal Gear, Sears Craftsman Endurable, etc.) off of 4 AA's or AAA's without shortening LED life by too much. The main reason is that I have 4 rechargeable AA's and AAA's, and I want to "use" them equally (if that makes any sense). Also, I never see batteries being sold in packs of just three...

So, can this be done, and if so, what do I need to mod? Resistors?

Bump... is there any way I could build a step-up or something to get a little more brightness outta this thing?

You can either use a resistor or a buck circuit to run LEDs off 4 batteries. I have made a few 3 and 4LED bulbs with resistors for 4AA lights and they work great, with a luxeon you would probably have to use a more robust resistor due to higher current demands.

Thanks for the reply! My other question is this, what do you mean by "buck circuit"? Also, does using a resistor mean my Luxeon will emit brighter with four batteris instead of three, or will I just get a little more run time with the rest of the energy being burned off as heat?

Inferno said:

Thanks for the reply! My other question is this, what do you mean by "buck circuit"? Also, does using a resistor mean my Luxeon will emit brighter with four batteris instead of three, or will I just get a little more run time with the rest of the energy being burned off as heat?

Click to expand...

some threads you should read ....

http://candlepowerforums.com/vb/showthread.php?t=72528
http://candlepowerforums.com/vb/showthread.php?t=77221
http://candlepowerforums.com/vb/showthread.php?t=93086

Unless your 3cells are sagging below the Vf of the luxeon using 4 cells to get more light would be overdriving them thus reducing the life of the LED.
Buck circuits are DC/DC converters that can at times be more efficient than a resistored approach, depending on how much headroom (voltage difference) there is between the LED and the batteries. The main advantage of 4 cells vs 3 is mostly longer runtime for lux1 and for lux3 the added voltage can help deal with the larger sag encountered from higher drive currents.