What modifications are made to the starter motor for a start stop system?

I am not sure how exactly they do it on those cars but I have seen many old golf carts that used a big DC generator as the starter as well. The oversized generator works well as a long duty cycle starter motor and also can quickly recharge the battery during the start and stop action of golf games. Being either direct or belt driven its always turning when the engine is running.

I believe this principal is used on some of the hybrids now too. I don't know exactly since I consider them overpriced clown cars for rich dummies and have not looked into them with any serious interest.

Paying $70K for a car the will save $10k in gas over a car twice its size that costs around $30K is stupid to me. The life expectancy cost numbers do not work in most of the hybrid cars favor.

I like the concepts but not the current size and prices. Maybe in 15 -20 years they will have something thats more in my interests. If I haven't built my own by then!

"many old golf carts" They haven't changed. We have a fleet of new carts where I work that are all gas powered with starter/generators. They are fairly low output, though, compared to an alternator. The "automotive grade" probably puts out more juice.

Thanks folks. When you say DC do you mean rectified 3 phase AC ie: a fairly normal alternator? The last d.c. generator (dynamo) I saw was on a car built in 1968. I think a big problem with using an alternator to start a gas engine is low speed torque, so I would expect an alternator capable of this to be larger, not smaller, than a typical car unit?

No, it's a starter/generator, acts as a DC motor for starting.

The toyota hybreds use a high speed starters & a sprag clutch [1 way bearing], which is how you get seamless transitions between gas & electric modes.

Thanks, interesting. Can you narrow that a bit in terms of models and engines? The full hybrids don't need a clutch so is this sounds like alternator/belt drive or starter motor?