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Making a usb rechargeable flash light

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  • USB
Last response: in Other Consumer Electronics
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May 15, 2014 9:28:45 AM

Looked all over and a million different scenarios but non that i am looking for.

What I am trying to archive:

3 LED's that can run off batteries and could be recharged from usb in my computer.
They should also be working while the usb cord is plugged in and is charging the batteries. I.e. Iphone.

This thing needs to be as small as possible and weigh as little as possible.
Preferably something lighter than AA batteries, maybe CR2032 not sure if those are rechargeable.

Any help would be amazing.

More about : making usb rechargeable flash light

May 17, 2014 9:56:18 AM

Yes but i need to make my own, or atleast understand what goes into making one.
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May 17, 2014 1:12:28 PM

Well in essence you would need 3 LEDs in series with a resistor to suit the battery voltage.
The smallest rechargeable batteries that are readily available appear to be ER35 and CR123 both of which are 3V and about half the size of a AAA.
This is where the problems start as you would need 5V batteries to charge directly from USB so if you were to use one of these batteries then you would need a 5V to 3V voltage regulator.This regulator would keep a constant voltage on the batteries whether the LEDs were on or off.
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May 17, 2014 9:02:10 PM

CR123 cells are NOT rechargeable. If you try, you could get a decent sized fire on your hands.

You need a smart charge controller for Li-ion cells; they need to be taken up to 4.1V and not below 3V.

I'd suggest using a constant current supply for the LEDs; resistors don't work so well when you change the voltage significantly.
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May 17, 2014 11:55:50 PM

Someone Somewhere said:
CR123 cells are NOT rechargeable. If you try, you could get a decent sized fire on your hands.

You need a smart charge controller for Li-ion cells; they need to be taken up to 4.1V and not below 3V.

I'd suggest using a constant current supply for the LEDs; resistors don't work so well when you change the voltage significantly.


You can get rechargeable CR123http://www.maplin.co.uk/p/cr123-lithium-ion-rechargeabl...
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May 18, 2014 12:16:39 AM

Those are; the vast majority are not.
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May 19, 2014 11:29:30 PM

Would any of these work? https://www.sparkfun.com/categories/54?page=all
Dont' you need special things to charge batteries?

Also, how would i wire the circuit? Usb -> voltage reg -> batter -> resistor -> led -> usb

Anyway you can draw one up?
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