MagSafe: Where is the charger ID stored?
The charger's serialization and capabilities are determined by the chip in the Magsafe connector.  The Mac also controls the LED, not the charger.


  Understanding the charger's ID code
  
  You can easily pull up the charger information on a Mac (Go to "About this Mac", "More Info...", "System Report...", "Power"), but much of the information is puzzling. The wattage and serial number make sense, but what about the ID, Revision, and Family? It turns out that these are part of the 1-Wire protocol used by the chip inside the connector.