LED batteries voltages and resistors?

Hi, I'm planning on making some throwies... I see that you can use a 10mm LED with a 3v watch battery without any resistors. Can I use a 5mm 1.7v LED with a 3v watch battery as well? Or could I hook 2 5mm 1.7v LED's to one 3v watch battery without using resistors? Is there any other watch type batteries that work well with a 5mm 1.7v LED? I don't want to connect them to AAA batteries lol... could hurt someone when throwing those. The reason I ask is because the 5mm LED's are like 1/10 the cost of 10mm LEDs. Thanks

phephq7 years ago
 LEDs have much more of a capacity to handle overvolting that you may think. color LEDs usually run at less than three volts, and should not have a problem running at 3v even if they are red (which usually run at just 1.5-2v)

though white white and blue LEDs (or two 1.7v in series), you would not be getting the full effect of the LED, as they run at 3.2v+ typically.

I would say using 1   5mm per watch battery would be best if you wanted to get the most from your LEDs

not that running them in parallel or in series will diminish their brightness due to the fact the lithium watch batteries, as well as most small-cell batteries, have a low current rating. This means that they can only supply a limited amount of current, which is the reason they are so safe to use on lower-voltage LEDs
remember that the actual geometric size of the LED bears no definitive link to its ampage voltage or wattage. Check the individual spec for the LEDs and go from there.
Test it and see