Power Systems One of the primary design specifications noted above refers to "maximum possible autonomy." Most commercial electronic systems assume that power is freely available, and thus exhibit rather sloppy management of loads (comparable to automotive and building design before people started thinking about fuel cost). I don't have that luxury. AC outlets are often days apart, and there's no convenient gasoline engine to keep a battery charged. Power, like my own human energy, is thus a scarce resource, and a fair percentage of BEHEMOTH's control system is devoted to its management. Curiously, this is one of the reasons there are so many computers: a good multitasking system could probably handle everything I need to do, but it would have to be active -- and drawing lots of power -- all the time. There are three power sources, two on the bike itself and two external. The primary source is a 72-watt array of Solarex photovoltaic panels, which forms the lid of the trailer. A small 10-watt panel graces the lid of my manpack, theoretically allowing me to unplug from the bike and still maintain reduced computing and communication capabilities although in practice, the SPARCstation ended up in that case, far outweighing the capabilities of a 10-watt solar module. A secondary power source was to have been a variable- reluctance motor-generator comprising the hub of the 16-inch front wheel. This could be set to continuously generate, but would steal precious power from my 1/8 horsepower body... more commonly, the plan was to use the VR system for regenerative braking. Squeezing the right-hand hydraulic brake lever would proportionally energize this system in an attempt to satisfy the braking request; if it's not sufficient, the hydraulics would do their job. Note that this would not only make power reclamation first priority, but would also prevent an electronic failure from having any serious impact on safety. Unfortunately, although we did work on this, it was never finished. The other two power sources are the external AC line (any international flavor) and an external source of automotive-scale charge current. A pair of 15 amp-hour Sonnenschein sealed lead-acid batteries are in the basement of the trailer, and another one is in the RUMP (Rear Unit of Many Purposes). An automatic change-over circuit allows trailer disconnection without glitching sensitive loads. Power management is in two layers. If no computers are alive, shunt regulators keep the batteries from overcharging. But Hall-effect current sensors at all key nodes allow one of the 68HC11 FORTH control systems to keep track of current flow, redirecting excess power to optional loads or simply disconnecting it when the batteries are full. The main bike power bus is 12 volts, but electronic loads call for lots of other voltages (mostly +5). To produce these as efficiently as possible, Power Trends integrated DC-DC converters associated with each load are switched in as needed, yielding 85-90% conversion efficiency and a minimum of unneeded overhead. These are all FET-switched by the trio of control processors as subsystems are invoked by higher levels. The graphical human interface, to be explained in a moment, can be called upon to display a dynamic pictorial representation of the whole power system, showing battery levels, all charge and load currents, and projected time until either full charge or total depletion (based upon sliding averages and historical trends).