LED conversion of light-up key

[DesktopDave]

I finally got around to resurrecting my dead light up key.  I'd seen a tutorial somewhere out on the web and decided to try it out myself.

All I needed was a 5mm yellow LED and a 3v lithium battery.  In order to fit it had to be smaller than the usual PC-type 2032 backup batteries (20mm dia, 3.2mm thick).  I found a thin 16mm battery (1612?) that worked perfectly inside the button.  I have spares if anyone wants to try this out.

Be sure you get a 3v lithium cell, some coin cells are alkaline with the usual 1.5 volts...not enough to light up a LED.

I took the key apart, removed the dead incandescent light, trimmed & bent the LED lead to fit, then found a foam button that would keep the metal BMW tag inside the button.  I clamped and drilled the light socket in the key slightly, and trimmed the LED flange a bit to make it all go back together.  BTW, that little bulb compartment is just about the perfect length for an LED.

I decided on yellow instead of red because it's far brighter.  The blue or white would have been nicer than yellow, but they require more than 3 volts of current that one lithium cell can provide.  You could stack two & overdrive the LED for brief periods.