LED Watch - Adding A Rechargeable Lithium Battery [Project COMPLETE!]

[iamdarkyoshi]

I've got a cheap ebay LED watch. It has enough empty space inside for a moderately sized lipo battery. It was originally powered by a CR2016 lithium cell, which ran low pretty quick, and I put a CR2032 inside instead. I'd like to make the inner watch module rechargeable once it goes dead, rather than replacing the battery.

Bu this leaves me with an issue: Voltage. The original cell was max 3.0v, and the cell I want to put in will be up to 4.2v

What regulator would be the best to use in a case like this? The watch is only on when I press the button, its otherwise sleeping. I chose red LEDs since they lit at a lower voltage than blue.

Long story short, I need a linear regulator that can drive the 3V watch from a 4.2V lithium cell. I've never shopped around for low power linear regulators before, figured I'd get some input first.

Thanks!

[edavid]

A fresh CR2016 or CR2032 can be 3.3V.  You might compromise and charge your Li-ion cell to say 3.6V.  I don't know if that would give you more capacity than an LIR2032.

If you want to use a regulator, an HT7530-1 would probably work well.

[iamdarkyoshi]

A fresh CR2016 or CR2032 can be 3.3V.  You might compromise and charge your Li-ion cell to say 3.6V.  I don't know if that would give you more capacity than an LIR2032.

If you want to use a regulator, an HT7530-1 would probably work well.

Just bought one of those and a 150mAh cell. Bought a 3.3v one actually. There is seriously more than enough space for a 150mAh cell in here... And space for a charge port...

Thanks for the suggestion!

[iamdarkyoshi]

Wow, 10 days and the parts already came
Imgur album: http://imgur.com/a/VyfTj

We'll have to see how long it lasts, but all I gotta do is pop the back cover off and plug it into a mini quadcopter battery charger rather than raiding another motherboard for a coin cell