View Single Post
  #22   Report Post  
Posted to sci.electronics.repair
Dave Platt Dave Platt is offline
external usenet poster
 
Posts: 379
Default Charging a car battery with 14V AC?

In article ,
Gary wrote:

I'm aware of that. I was asking about how the polarity of the
AC output affects how the capacitor should be placed?


AC has no polarity.


Exactly my point. So does it matter how the capacitor is placed
across the output leads?


No. If it's truly an AC output, the capacitor will explode equally
well with either orientation.

Unless I am missing something here, you're trying to do something
futile... you *cannot* charge a car battery using an AC waveform of
the sort you'd get out of a transformer. The net amount of charge
delivered into the battery will be zero, with or without a filter
capacitor... all you'll do is heat up the battery to no good effect,
and (if you install a filter capacitor) overheat the capacitor and
make it blast its guts out all over the room. This is spectacular but
not terribly useful :-)

You *must* rectify the AC (either half-wave or full-wave
rectification). Once you do so, you no longer have AC - you have a
pulsed DC.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!