Need explanation with bulb voltage please.

Other Types of Lights LED Light Bulbs
1

Hey guys,

So I have two XML bulb from solarforce. One says it has 3.7V and one has 2.7-9V. Can anyone please explain the difference between those two bulbs? Advantages/Disadvantages?

And also, while not in the topic of LED bulbs, can anyone please explain a typical 18650 battery with 3.6v (if there’s any relation to the voltage of the bulbs).

Thank you so much!

2

3.6 or 3.7 is the mid point voltage level for li-ions. Batteries don’t provide a constant voltage so they’re sometimes labeled with the average voltage across their discharge range. Normal 18650s are actually 4.20 volts fully charged and as low as 2.5 - 3.0 when fully discharged.

You 3.7V bulb / dropin can only use one 18650. The 2.7-9V bulb / dropin can use one 18650 or two 18650s.

3

Hi Halo,

Thanks for the reply. I have a follow up question please.

What would happen if I use two 18650s on my 3.7v bulb?

Thanks!

4

It will burn out the circuitry and possibly the LED which could lead to smoke and possible fire hazards

5

Thanks Bort!

Been playing around with my solarforce stuff, and wanted to know (and verify) these stuff.

6

tabs, those aren’t “bulbs” — those are dropin modules that contain some kind of electronic driver circuit (the thing on the battery side) and some kind of LED 3emiitter (the thing on the glass side).

Those are contained in a piece of metal sized to “drop in” to the Solarforce and other flashlights, usually with a big spring around them to fill the space between “drop-in” and flashlight head.

LEDs are pretty similar — they want 3.7volts or thereabouts. So the driver circuit takes whatever it’s meant to take in the way of batteries, and converts that to what the LED should be getting.

You know how batteries add up? Take alkaline AA cells. Each is 1.5v. Two in series add up to 3v.

Lithium-ion cells are about 3.7v individually. so one of them will drive a LED (still might burn it out if run for more than momentarily, so you still need a driver circuit).

7

Hi hank,
Thanks for the clarification, trying to learn more.

8

I recall this is a good intro: LED - Flashlight Wiki
Others may have other suggestions for a good “start from the beginning” that puts everything together.