Flashlight USB mod

[IR_Efrem]

So I took apart a flashlight that holds 4 AA batteries. I currently have 4, 2400mah (NiMH) AA's in it. This is nothing more than a portable USB type power source for a passthrough. I pulled a dual USB plug off an old motherboard and soldered a couple short wires to where the bulb used to plug in. The cap doesn't even thread on with 1 full turn, so the wires don't twist much at all. The hole was cut with a Dremel and the plug stays in place with JB Weld (epoxy). Only took a few minutes to complete and it works good. My thoughts were to use this while camping so I don't need to fashion additional adapters and in emergencies..... well double AA's are cheap enough.

 

[t3hp00ky]

LOL, nice little camping mod
Good thinking

 

[IR_Efrem]

This is not for a straight PT, because the batteries are not protected. But just as a power source for charging the battery in a normal PT. I think it will serve my intended purpose well enough. =)

 

[Tanner S Hyde]

Just thinking about that... you could use an unprotected PT, and a 5V reg, and have DAYS worth of battery in something like that... very cool

 

[IR_Efrem]

I had to put up the disclaimer. No one here runs unprotected right? So..

Do not use this for an unprotected Passthrough. If you do not know the difference between protected and unprotected do not attempt this or build anything similar...

And yes it does last for days. =)

 

[IR_Efrem]

No need for me to add a voltage regulator. I am pleased with the 4.8v.

Besides you want a bit more voltage for charging a passthrough battery. Load voltage drops to just below 4volts anyway. So this is about perfect for even a non protected passthrough. It would be advisable to add a protection circuit though; something that will not allow more than 2amps, this would make it a decent protected circuit.

 

[Tanner S Hyde]

Sorry for the confusion, I meant at that size one could easily stuff several protected batteries in there,and use it for a 5v pt

 

[IR_Efrem]

4x 3.7v batteries?

14.4 volt

Does decreasing the voltage with a regulator increase run time?

 

[Tanner S Hyde]

Well, without getting crazy on the math... if you had say 1000mah @ 10V, and you reduced that to 5V, you'd expect ~2000mah, not withstanding that regs do waste SOME energy...

 

[IR_Efrem]

I'll have to take your word for it my friend. I never knew if cutting back the voltage would increase battery life in the prescribed manner. There are some highly efficient FET's out there that wouldn't waste hardly any energy at all. This definitely merits some more thought. I don't much care for working with l-ion batteries but I just might, who knows. I found a source for PCB's for the cells. Now to design an efficient regulator. Perhaps one with variable control.

This is my next project in fact: a straight passthough (don't like large batteries up by my face) with a variable voltage control.

 

[IR_Efrem]

I'm thinking a dual LM317 (they can be stacked to handle 3AMPS) and a potentiometer.. Hmm the possibilities.