[DeTomaso] electrical question - alternator

[SOBill at aol.com]

Lee,
 
Here's the deal:
 
The alternator will put out about 14 volts to charge  the battery. If the 
battery is completely flat, the alternator will put  it's max rated current, if 
the engine rpm is high enough, to rapidly charge  the battery. As the battery 
charges, the alternator output current will slowly  drop off.
 
The Pantera wiring was (more or less) designed around an alternator  with a 
max of 65 amps. If you have installed a 200 amp alternator, a dead  battery 
will draw 200 amps and this will definitely stress the wiring between  the 
alternator, the ammeter and the battery. Will it be dangerous? Probably not.  BUT if 
you hold the revs up and pump 200 amps thru the OEM wiring  until the battery 
is fully charged, the wiring will no doubt get  warm.
 
A second consideration is just after you start the engine. The  battery will 
be partially discharged by the starter and the alternator will  put out max 
current. But the battery will quickly regain a full charge and the  world will 
be at peace.
 
The third situation is when the battery is fully charged but the AC  fan is 
at max, all three fans are running, the HiFi is honking full tilt, and  the 
Baja road lights are at max. The alternator will be supplying this load via  the 
wire between the alternator and the ammeter and this wire is sized for 65  
amps. Will it be dangerous? Probably not. If you smell something hot, turn a few  
accessories off until the air clears.
 
The final solution: replace the wire between the alternator and the  ammeter 
and between the ammeter and the battery with a bigger wire. A 10 foot  long 
wire carrying 65 amps should be a #6. A 10 foot long wire carrying 105 amps  
should be a #4. The other wires in the car are fine as they are. Then replace  
the OEM ammeter with a voltmeter.
 
SOBill  Taylor
sobill at aol.com  

 
In a message dated 8/4/2008 6:45:58 P.M. Pacific Daylight Time,  
lee_farrell at sbcglobal.net writes:

 
I was talking to Mike about my seeing on forums recommendations to  upgrade 
the car's wiring after putting in a new, more powerful  alternator.   I was 
saying that the increased alternator rating per  se will not lead to more 
current.   More loads leads to more  current.
 
Mike (who claims he doesn't know electricity....) pointed out what about  
during starting.   Could a new alternator put out its higher  current limit 
during starting?   so that some wires would  in fact see higher current with just a 
new alternator.    I was  assuming the alternator is barely functional during 
starting, given low RPMs  and low system voltage.   
 
Can you provide some guidance on this??
 
thanks
 
lee  farrell







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