the best alternator

[FrankenSchwinn]

since there is no driving/transportation forum anymore, i'm asking the gear heads and mechanical geniuses on this forum:

is there a car alternator that could charge up some 72volts relatively well?

i ask because i'm in the planing process for an electric motorcycle and i have to say that the range is what i would like to improve on. past projects all over the net have shown up to some 30km but would an alternator hooked to the engine work?

i haven't seen one on any electrical project though, so i was wondering if anyone here is knowledgeable with vehicle electricals like car stereos etc.

[Zico]

You could enquire here.. http://www.streetcharger.com/streetcharger.asp

Looks like they offer an alternator that will charge a 72 volt system providing your set-up consists of 6-12 batteries running in series?

Edit- Maybe not- looks like they are for 'hydraulic' batteries and the "street charger" is actually powered by a 12 volt car battery which in turn is charged by a normal alternator.. hmmmm... :\

[Zico]

Found an EV site which you may find of interest.. http://www.evalbum.com/build#buyparts

Quote from the 'Building an EV' section

"Is there anyway to make it recharge itself while driving?

In a word, NO. Driving generators off the wheels, adding a windmill on top and similar ideas are often suggested. The problem is the increased drag from such items would be several times greater than the added power they would generate. It is a nice idea, but it won't work. There have been some folks working with pusher trailers to allow the EV to become a hybrid for highway use. You can find some info on one on JB's webpage - http://www.jstraubel.com/EVpusher/EVpusher2.htm "

This would explain why a lot of the current hybrid cars only recharge themselves using re-generative braking.

[Rollo]

is there a car alternator that could charge up some 72volts relatively well?

The answer to your question in short is: NO - because car alternators aren't designed to do it.

Virtually all automotive electrics for the past 25 years at least have all been 12 volt. Most alternators are designed to give a charge of 13.8V though anywhere from 13.4 - 14.2 is perfectly acceptable.
24V electrics in cars went the same way as the Dodo, Kate Moss and Rocket lettuce - they were a good idea once upon a time... but not now.

What you want to do is "step up" the voltage and to do this you'll need a coil and/or a transformer.Because you're going to need a transformer to step up the voltage from 12V to 72V, I'm wondering whether the weight required is actually worth the effort on a bike.

[bowler]

are you using 12v batteries?
If so you can charge them in parallel and then draw on them in series.
The size of the gear needed will probably make it very heavy, see above

[FrankenSchwinn]

i'm more and more thinking honda goldwing frame stripped to its bare minimum so weight would not be that much of big deal..