Recently, I had the pleasure of driving a Toyota Prius on a 500 mile trip. Some of the route took us over large hills.
Ideally, at the apex of a large hill, the hybrid system would have completely depleted the battery (and thereby allowed the gas engine to work a little less hard). Because, on the way down the hill, I'm going to build up more than enough kinetic energy to fully recharge the battery. And once the Prius has fully recharged the battery, it starts throwing away kinetic energy like a regular car.
But, of course, the car has no way of knowing that I'm about to go down a large hill. Or does it? If I've entered my destination into the GPS system and the GPS system has fine-enough-grained elevation data then the car could know it's nearing the top of the hill and it's OK to splurge on battery usage. Even if I haven't entered the destination into the GPS system, local elevation data could improve the system's prediction of upcoming driving conditions.
Maybe it'd gain you a mile or two per gallon on a hilly trip.-- joee, Sep 29 2005 Toyota Prius http://www.toyota.com/prius/ [joee, Sep 29 2005] Excellent thinking! Useful predictive computing is a fascinating area of study.-- bristolz, Sep 29 2005 Also, internal combustion engines are less efficient at higher altidudes due to the lower oxygen density in the air, which means this idea is probably pretty good.-- BJS, Sep 19 2006 What [bristolz] said. <sniff>-- pertinax, Sep 19 2006 Same issue with my Civic hybrid, but why not just install a simple toggle switch to manually control the battery charging? Up, works like normal. Down, doesn't recharge until it's critically low.-- J Vander, Nov 13 2006 Maika'i !! (Great!, swell!) This would work well in Hawaii, with all our hills, mountains and tunnels. The Prius is also getting more popular here, although not as much as a truck. They should make a hybrid truck.-- twitch, Nov 13 2006 I would rather have simpler system which would not be based off of GPS mapping technology.
The system I have in mind is one that would be based on a gravitational sensor (like the ones currently used in some LandRovers and Subaru's I think?) which would sense the angle of the vehicle in relation to the direction of gravity to determine weather the vehicle is on an incline, or on a decline. It would also work with the vehicle's central processing unit and the speedometer to compensate for vehicle acceleration.
The system which was previously described would not be predictive, which I do not believe is necessary. Also, it would not depend on rarely updated Satellite information.-- BJS, Nov 14 2006 Even easier than a gravity sensor, which would switch on and off frequently, you could rig your gps system to read a topographical map. Tell it what to do on a certain grade of incline, efficiency issue solved.-- Bighongry, Oct 08 2007 What some of the annos seem to miss is that you need not only data about your current inclination, but what lies ahead. That way the car can most efficiently use up its existing battery charge, because it can predict future opportunities for downhill recharging. If there aren't enough good downhills ahead, it knows to keep some charge in reserve.
An alternative non-GPS way would be for the car (and an accelerometer/inclinometer) to learn your regular routes eg home->work. With a linear map of the grades along this path, each pass after the first can use grade prediction to manage charge.
This is brilliance. Have a bun.-- BunsenHoneydew, Oct 08 2007 [+] Although using GPS is the easiest way to measure one's current altitude, there are (at least) two other ways of doing that task that don't require satellites.
First, use a pressure altimeter. Basically, measure the air pressure and do some math. It's not always accurate, since weather systems produce air pressure changes, but it's simple.
Second, dead reckoning, as with an inertial navigation system. This has the potential to be more accurate, but it requires constant measurements, which results in continuous electrical power use.-- goldbb, Jan 29 2013 random, halfbakery