The alternator on our Odyssey does "upshift" and "downshift" depending on load. I don't think it ever totally kicks off, but it might...

That is basicly how the built in voltage regulator works, at least the alternator on a honda, and alot of other cars, will not put out anything without a feild voltage, cut that power, and it's just a spining mass, and that voltage varries depending on the battery voltage, and that varries depending on electrical draw, if you do a search you will find a page that I started where I put an amp meter on my battery, and turned on differnt parts of the car, the computer and coil my civic draws a minum of 80 watts, solar is $5 per watt, and on average you might get 4 hours of solar per day, so that $5 per watt will get you 4 watt hours per day, average person drives 20 miles per day at something like 25mph average, so lets just round that up to an hour of driving per day, so $100 worth of solar to alow you to drive one hour per day, just for the cost of solar and that might be half, so $200 so you can drive 20 miles a day without lights, or a vent fan or radio.

GM started doing this in about 2005. It's one of the things they did to try and boost mileage on the trucks and SUVs, along with installing electric fans on them from the factory. The computer monitors and controls alternator output vs battery load. And, usually when GM does something small like this that puts something under the control of the computer on one vehicle, they do it to all of them, to make them more complicated to work on. I mean, who's going to want to replace their own alternator when they know it's computer controlled?

hey! thats my idea! but i want to try this out with 2 baterys and my roof covered in solar panals

Telco knows the story but Honda has been doing the same thing at least since 1992. The ECU of my 92 Civic VX shuts the alternator off when it's not needed. The alternator is only shut off at low speed (50 mph or less) and the headlights and/or AC must be off at all times. How do I know this is true? The helm manual for the Civic tells you and I know because I installed an aftermarket voltmeter under the dash by the fuse box to keep track of it. The voltmeter drops to 12V when the alternator shuts off and jumps back up to 14 V when the alternator is engaged again. The alternator is running constantly at high speed - 70 mph because the distributor needs the voltage to spark the cylinders. You can't run on battery power too long without draining the battery. I know, boy do I know this!

Solar panels? Great concept but not enough power density. A fuel cell or other high density power source would do it - Hey! how about a belt driven alternator. (I know I'm being a smart a**)

On a carburettor car, you can drive a long long way without alternator (e.g. I drove 60 miles once, with a few starts, in a carb car). The ECU in my car actually gets hot to the touch, so this is a waste of power if running without an alternator.

How about converting some of that waste energy in the exhaust system into electricity? That could be done with thermopiles or a Sterling engine.

Speaking of waste heat, I looked at using it to power steam-driven air conditioning, but the apparatus would be huge. So now I'm thinking an absorption cooling system and some good reflective window tinting may keep me cool, and not use any gasoline. And I could toss all the weight of that broken A/C unit. hmmm...