DIY mild hybrid idea

[pete c]

Has anyone out there looked into modifying a car's charging system so that the alternator could be used to help push the car along and recoup a little energy through regenerative braking.

Do alternators make decent motors? Could an alternator's voltage be upped for greater power without huge conductors?

Could an alternator be powerful enough to serve as the starter so you could save a few pounds deleting the starter?

[Ecky]

I'm fairly certain most alternators are not suited to the task, but I'd love to tinker with such a system. You would almost certainly need some extra batteries, probably an auxiliary set which is only used for assist.

[sendler]

Mercedes has computer controlled charging which leaves the battery intentionally a little low all of the time and only charges when it is fuel efficient to do so like when braking.

[pete c]

Originally Posted by Ecky

I'm fairly certain most alternators are not suited to the task, but I'd love to tinker with such a system. You would almost certainly need some extra batteries, probably an auxiliary set which is only used for assist.

From the reading I've done here on alternator cutout mods, they do put a fairly decent drag on the engine. If this is the case, they should be capable of putting a similar boost into the system.

I think this idea could work quite well with very light cars such as metros with a larger car's alternator fitted. You would definitely need added battery capacity, or at a minimum, go to a deep cycle type battery.

One possibility would be to add a Li or Nimh pack to supplement the regular battery. Make it removable for weight savings during highway trips when a hybrid system is just extra weight.

[drmiller100]

alternators make crappy electric motors.

starter motors are better, as are golf cart motors.

[mort]

Originally Posted by pete c

From the reading I've done here on alternator cutout mods, they do put a fairly decent drag on the engine. If this is the case, they should be capable of putting a similar boost into the system.

Hi pete c,
Using the alternator that comes on a car will be expensive. The alternator makes AC. To drive it as a motor requires an AC driver circuit capable of delivering a 3 phase ac signal at the right frequency and higher voltage than the stator would develop as a generator. It's a fairly simple motor controller if you design motors and are making thousands, but a one-off will be daunting. In addition car alternators are not designed to be efficient. Low cost and durability are more important. For this idea to really work you need a motor-generator designed for the job.

-mort

[Daox]

Even if you could use your alternator as a motor, its going to be good for what... most alternators put out ~70A @ 12V. Thats about 1 hp, woohoo.

What you're thinking about is very close to what GM did a few years back with its BAS (belt alternator starter) mild hybrid system. Google it for more info.

[pete c]

Originally Posted by mort

Hi pete c,
Using the alternator that comes on a car will be expensive. The alternator makes AC. To drive it as a motor requires an AC driver circuit capable of delivering a 3 phase ac signal at the right frequency and higher voltage than the stator would develop as a generator. It's a fairly simple motor controller if you design motors and are making thousands, but a one-off will be daunting. In addition car alternators are not designed to be efficient. Low cost and durability are more important. For this idea to really work you need a motor-generator designed for the job.

-mort

good points, mort. thanks. guess it pretty well rules out the alternator idea for low cost DIYers, unless maybe they are EEs with experience in AC controllers (not me).

[pete c]

Originally Posted by drmiller100

alternators make crappy electric motors.

starter motors are better, as are golf cart motors.

a golf cart motor might do the job. starter motors are made for very short high torque applications. not really suitable for this.

[pete c]

Originally Posted by Daox

Even if you could use your alternator as a motor, its going to be good for what... most alternators put out ~70A @ 12V. Thats about 1 hp, woohoo.

What you're thinking about is very close to what GM did a few years back with its BAS (belt alternator starter) mild hybrid system. Google it for more info.

Yes, I do recall reading about that a few years back. Seemed like a very good idea. Did GM give up on it?