Power supplies for desktops are designed to provide a constant voltage output over a range differing power requirement the system needs. The typical wall wart is designed to produce a specific voltage at a specific level of power usage. While it is possible to monitor the amperage used by a system it is easier and cheaper to monitor the voltage. This is the case with the PowerBooks since it is possible to get a voltage reading through software. In a simple power supply sufficient current is supplied to power the device. On an inexpensive supply increasing the current (amperage) demands will result in a drop in the supplied voltage. Generally computer components suffer no long term harm from a voltage drop, and the most common scenario is for the power supply to fail before any harm comes to the device it is powering. Certainly with the Duo's ability to read the voltages of the system it is possible and likely the system can use various power saving measures to compensate for this. Effectively sensing a drop in the supplied voltage it reacts by reducing the power it is consuming. In a very primitive way battery charging is self regulating. In order to charge a battery it is necessary to supply sufficient voltage to overcome the internal resistance of the battery. If a power supply's voltage drops below this threshold then it simple becomes unable to charge the battery there by no longer needing to supply any current to the battery. William Ove >However, I'm not sure I can see a way for the 2400 to recognize the >amperage of the power supply anyway, other than knowing when there ain't no >more (if you see what I mean). Then again this is pushing the limits of my >electrical theory; if there's some theoretical way the PB could tell what >the maximum available current and power is (without attempting to exceed >it) I'd be interested to know. I can imagine that the charging circuit >would shut down when there wasn't enough "leftover" power available (ie. >when it had exceeded the capability of the supply). > ---------- Duo/2400 List, The friendliest place on the Net! A listserv for users and fans of Mac subportables. FAQ at <http://www.themacintoshguy.com/lists/DuoListFAQ.shtml> Be sure to visit Mac2400! <http://www.sineware.com/mac2400> Dr. Bott LLC | Get a LapBottom with new �GRIPPIER� gripper pads! | http://www.drbott.com/prod/lapbot.html $23.00 Midwest Mac Parts <http://www.midwestmac.com> | After-market parts for Macs. Fix your ticking dock for $59 w/ trade-in of PS. 888-356-1104 PowerBook Guy is | Click here! Everything PowerBook! | http://www.powerbookguy.com
