[Healeys] (no subject)alternator

[Bob Spidell]

Not unless the alternator is overcharging.  The current flow to the 
battery is determined by the voltage of the source and the internal 
resistance of the battery (i.e. E=I*R, or I=E/R).  In other words, a 
battery in a given state of charge will sink the same current from a 
generator producing a nominal charging voltage (e.g. 13.8V) as from an 
alternator producing the same voltage.   If the internal resistance of 
your battery is low enough--close to a dead short--a generator can 
produce enough current to fry the charging wire.   Remember also that 
the battery has to supply enough power to excite the field coils 
(generator) or armature (alternator) to provide current in the first 
place, so a battery near a dead short will a) not start the car in the 
first place and b) not supply enough juice to keep it running.  If you 
jump a car with a dead short battery from another car or battery, the 
500+ amps available will fry a pretty large cable (check how hot the 
cable to the starter gets after only a few seconds of fruitless cranking).

An alternator or generator isn't meant to be a current-limiting device 
(unless it's Lucas ;).  That is accomplished by the total load of all 
your electrical devices or, in a pinch, a fuse, fusible link or circuit 
breaker.


bs


Brits'n'Pieces (Eric Frenken) wrote:
> Charlie,
>
> that's a true concern. As most (not to say all) alternators have a
> considerably higher output than the original dynamo, you should have an
> appropriate gauged cable between your alternator and the battery for these
> high currents.
>
> Best regards
>
> Eric
> Heinsberg/Germany
> http://brits-n-pieces.com
>
>
> Norman or anyone else,
> I have heard that most modern alternators can put out more current than the
> wiring in an Austin-Healey (or most other old British cars) can handle.  If
> the battery is discharged the alternator will be supplying that current to
> charge the battery for some relatively long period of time.  Is this a
> concern?  Is there a certain output that Healey owners should not go above
> when selecting the alternator to convert to?
> Thanks.
> Charlie Baldwin (electrically challenged)
>   


-- 
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Bob Spidell           San Jose, CA            bspidell at comcast.net
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