Will a 3v lithium primary be able to properly power a device intended for 3.7v li-ion

[jzmtl]

I'm thinking since I already carry lithium primary for my lights already, would I be able to splice one into a mini usb plug, and use it as emergency backup power for my cellphone? I suppose the splicing part won't be a problem, just find out which two of the five contacts are + and -, but would a cellphone able to powerup and function on only 3 volts, consider it's designed for up to 4.2?

 

[Probedude]

Probably not. Lipos are essentially dead at 3.6V/cell when lightly loaded. A primary at 3.0V would be considered as excessively discharged to your phone and likely it would not power up.

 

[jzmtl]

Aww, well. I don't suppose there's a led driver somewhere that boost the voltage to around 3.7 to 4.2 eh?

 

[Probedude]

Aww, well. I don't suppose there's a led driver somewhere that boost the voltage to around 3.7 to 4.2 eh?

There are dc-dc switching IC's that will boost the voltage. If you want to go that route, you might as well double up the 3V lithiums and then use a DC-DC buck converter IC to drop it down to a lipo voltage of ~ 4V. It would last longer.

Go visit National Semiconductor's website and fiddle with their switching power supply part finder and see what's available.

 

[jzmtl]

I was hoping to keep this as small as possible, so the circuit would slip into pocket unnoticed. I carry spares for my single cell light only so they may not may not be in the same state of charge so double up is not possible. I'll go poke around and see what's avaliable.