Ask Max: Bikes powering Macs!
This may be something you haven't covered yet.I'm an elementary school librarian with an iMac and iBook lab. I'm trying to get the kids to put some of their excess energy to good use by having them ride recumbent bikes and simultaneously generate enough electricity to charge a 12" iBook (which they'd be using at the time). Right now they put out up to maybe 30 volts or so (no load), which drops to about 25.5 volts when charging two decent-sized (4.5 amp?) 12 volt gel cells, wired in series. I've briefly run this, using a cable from a dead Apple charger, into the iBook and get the battery to charge while the computer is being used. Nothing fried thus far! I'm working on a basic voltage regulator circuit to drop this down to the charger's rated 24 volts, but I was wondering how many volts that a/c adapter/charging port can handle before I have to worry about cooking something. These are the dual-USB port iBooks, if that matters.
John this is a great project and it is the first time I have heard of a school doing this. The adapter's power outpoint for white G3 iBooks is 45W 24V 1.875A. The power threshold that an iBook will take is hard to determine. Wattage is not an issue because the iBook will only consume the power it needs. You are going to want to keep the charge below 3 Amp. I would suggest using a car fuse to protect the iBooks in addition to the voltage regulator. The specks are the same for G4 iBooks but instead it has a 2.7A output. I have run G3 iBooks with G4 iBook power adapters and have seen no negative effects. So if the output is capped at 2.7A or 3.0A you will probably be in good shape.I hope this helps with your project. Please send me some pictures and updates on the success of your experiment.Jacob Loeb