BMW Glovebox Flashlight Upgrade to LED w/ Lithium Cell
I've been tired of my glovebox flashlight being weaker than my cell phone 'flashlight' (flash in flashlight mode) and decided to do something about it and retrofit an LED.
A very good guide has been written before here, but it's a bit outdated. That guide uses a NiMH cell with lower capacity than a Li-Ion and goes with a conventional LED driven directly by the battery pack. This makes things easy from a charge and regulation standpoint because the battery pack is essentially connected directly to the supply through a resistor and no regulation exists for the LED (the current from the pack is low enough not to blow it).
I decided to step things up a bit.
My project uses a single 600mAh rated 10440 Li-Ion cell as a power source. This is almost double that in the previous project. The lithium cell requires special care for charging, so the 12v supply to the charging socket is stepped down to a regulated 5v by a 1.5A rated voltage regulator. This feeds a MAX1555 single cell lithium charger which controls the cell's input and cuts off the current when it's topped up. This is VERY important to avoid an explosion in your glovebox (hooking a lithium cell up to the 12v supply would be BAD).
I used a Cree XM-L LED controlled by a 350mA rated AMC7135 based driver board. At this low of a current the LED runs very cool for extended periods of time without extra heatsinking. It also ensures the light has a theoretical run time of almost two hours.
You'll see in the pictures that this first light was hacked up quite a bit as I was testing different circuit layouts and battery types to see what was the maximum I could fit. I plan on building some more since I have a whole bunch of extra parts and they'll look much nicer inside. Not that you can see from the outside. The factory switch remains completely functional in this one, though I'll be improving how it's set up in the future. It still latches on even as is.
Check out the attached pictures and I'd appreciate any feedback!
edit: Title changed to make the thread appear in more searches
Last edited by waehrik; 06-26-2013 at 08:05 AM.