Motorcycles have used permanent magnet alternators for some time. The trouble with them is that they have to shunt excess energy to ground. Not as efficient way of making power as one would think.
The nice feature of an energized rotor is that you cut down the rotor current to a level that the system needs. Basically if you don't need energy you are just freewheeling the alternator. I cringe at a 90 dollar battery replacement every 4-5 years. Now I have a 500 dollar battery? Dang.
As far as purchasing a new car for better mileage, what is the economy in spending 20,000-40,000 dollars to save 4-800 dollars a year. Something like a 2% return on your investment.
Go for it become a beta tester. Once it is 3-4 years old and fixed, I might buy a used one.
Quote:
Originally Posted by rfdesigner
The 'stop/start' systems are pretty smart.
What's happened is that, I think Bosch, has developed a system where the starter motor and alternator has been combined, AND (important bit) they have done away with the field coil and gone permanent magnet which gets you from 65% efficiency up to 90%. Then they put in a fast charge/discharge battery system and a computer and suddenly your 'alternator' is producing power at 90% efficiency when you break, storing excess so when you accelerate again you don't load the engine at all.
Once you've done all that then you can get electric air-con electric power steering etc. all driven off 'breaking energy'.. and meaning the engine efficiency at low power is substantially better.
An example is the Volvo S40 1.6Drive start/stop which has 84mpg exurb vs the non-stop/start which is 74mpg.
Derek
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