<VV> alternator

[Frank DuVal]

And neither do generators! Generators also use electromagnets to 
operate, hence the field coils. The iron in generators does have a 
little residual magnetism, hence the need to "polarize" the generator. 
This polarization gives it the "jump start" of magnetism to start 
charging (and to charge in the correct polarity).

But, If the alternator is working, then when the battery is 
disconnected, the alternator keeps right on working! It supplies its own 
power at that point.

I think the residual magnetism in an alternator will also allow it to 
self start. Something I should try. But it will wait till after the 
Virginia Vair Fair.

BTW, most push starting on cars relies on a weak battery, not no battery.

Frank

Hmm, tech session at the vair fair?

On 5/13/2011 12:08 PM, Michael Kovacs wrote:
> Old answer. Alternators have no permanent magnets. They get the power from the
> battery to activate the electro magnets to allow the alternator to generate
> current.
>
>   If  you disconnect the battery, where does the alternator get the power to
> allow it to generate the 12V?
>
> When I was in the USAF (about 40 decades ago) our 1961 Ford "Follow Me" trucks
> were specially equipt with alternators. If someone forgot to turn the lights off
> and killed the battery, push starting did not work as the alternators would not
> creare any voltage.. Motor Pool had to jump start them.
>
> MIKE KOVACS
>