Battery help, questions?

[Pontiaker]

Maybe someone can point me to some info for a newbie? Alot of the stuff I find is way over my head for a normal non engineer type of hobbyist?

One of my first questions is I have a light, lets just say a generic light that has a P7 bulb and is made to run on either 2 primary 123 batts or one single 18650. Its about the same brightness with either batts running the light.

The two 123 batts are 6v right?

The 18650 is 3.7 v?

How can the light be so bright with either batts? One is less volatge but one has higher run amperage, this is measured in MAh?

So the two 123 batts can only release so much of their power to the LED while the single 18650 can release more power, more MAh to the LED?


Is this basically how it works?
Thanks!
Matt

 

[Mr Happy]

One of my first questions is I have a light, lets just say a generic light that has a P7 bulb and is made to run on either 2 primary 123 batts or one single 18650.

That's not just any old generic light, that is really quite a sophisticated light.

What happens is there is a complex piece of electronic circuitry between the battery and the bulb. This circuit takes just the right amount of electricity from the battery, then it converts it electronically to the voltage and current the LED needs (which is different from what the battery supplies), then it feeds it to the LED. In many circuits, it monitors what the LED is taking and adjusts the current to keep the LED running at constant brightness.

You may consider it amazing that such a complex circuit can be hidden inside a tiny and often inexpensive light these days.

BTW: A P7 is not actually a bulb. A bulb is one of those old fashioned things that people used to find in flashlights many years ago. They were made of a round glass envelope containing either a vacuum or some special gases, with a wire inside that would glow white hot when current was fed through it. They got the name "bulb" because they were often bulb shaped.

 

[Bullzeyebill]

Gee, Mr Happy, you got the poor incan "bulb" dead and buried. :mecry:

Bill

 

[Pontiaker]

That's not just any old generic light, that is really quite a sophisticated light.

What happens is there is a complex piece of electronic circuitry between the battery and the bulb. This circuit takes just the right amount of electricity from the battery, then it converts it electronically to the voltage and current the LED needs (which is different from what the battery supplies), then it feeds it to the LED. In many circuits, it monitors what the LED is taking and adjusts the current to keep the LED running at constant brightness.

You may consider it amazing that such a complex circuit can be hidden inside a tiny and often inexpensive light these days.

BTW: A P7 is not actually a bulb. A bulb is one of those old fashioned things that people used to find in flashlights many years ago. They were made of a round glass envelope containing either a vacuum or some special gases, with a wire inside that would glow white hot when current was fed through it. They got the name "bulb" because they were often bulb shaped.

:DI think I only called it a bulb once! yeah I meant LED....

So the driver is doing all the work. Or on a simple light the resistor cuts the voltage down to what the LED or bulb can use to run at whatever brightness you want it at? Iam guessing the resistor does the job but a driver does it much better, better batt life, better reguation, etc?

 

[Mr Happy]

So the driver is doing all the work. Or on a simple light the resistor cuts the voltage down to what the LED or bulb can use to run at whatever brightness you want it at? Iam guessing the resistor does the job but a driver does it much better, better batt life, better reguation, etc?

Yes, when the battery voltage is higher than needed by the LED a resistor can be used, but it is not the most efficient and it does not regulate brightness very well. Electronic driver circuits can handle a wider range of battery voltages and can step the voltage up as well as down.

 

[Pontiaker]

Thank you very much for the help. I want to start modding/making some simple lights to play around with, learn how its done. I will have to look into using drivers,etc...
Thanks!
Matt

 

[mdocod]

Lets say, for the sake of argument, that this particular light being discussed, does not have anything but maybe a low value resistor in it: (this is actually more likely than actually be regulated, but you never know till you take it apart or check it against others findings)... The CR123s would start to experience major voltage sag as the current shot up to ~2.5+A, at ~3A the CR123s would be down to ~2V per cell anyways, so it wouldn't take much of a resistor to keep things running smoothly. An 18650 would not run as much current through the LED, in fact, probably 30%-50% less, but you see, LEDs increase in efficiency as you reduce power input, combine that with the fact that it takes about a 30% difference in output to see much difference with a human eye, and you realize that on an 18650 it may very well be measurably dimmer, but you can't see it.