[DeTomaso] Alternator test data

[David D Fisher]

Thanks to John for catching my typo..
 
"and a 4guage line from the ammeter to the fuse box. "   should have read " and a 4 gauge line from the Alternator to the fuse box"
 
Upon rereading,  it looks like I better turn on the spell checker too!  :-)
 
 

________________________________
 From: David D Fisher <fisher95020 at yahoo.com>
To: Pantera mailing list <detomaso at realbig.com> 
Sent: Saturday, September 15, 2012 10:02 PM
Subject: [DeTomaso] Alternator test data
  
Ok,  I promised this would be my last entry on this subject. I ran tests today on my 1 wire alternator setup and am sharing with anyone interested.
 
 
First I wanted to know how much current each system was drawing.  I put it in a table for my future reference, and it's here if anyone has interest.
 
Punch line,  I pull 56Amps with everything on.  I ran this at both 800 rpm and 2000 rpm
 
http://www.poca.com/index.php/gallery/?g2_itemId=38007
 
 
Probably more interesting,  I ran the test of what happens if you disconnect the battery while the alternator is running.  Again run at 800 and 2000 rpm.
 
Punch line,  Voltage has a little spike but stays at 14.X volts and the car (all the systems in the car) don't mind having the battery circuit connected and disconnected.   NOTE: This is a one wire setup and you should run your own test on your own alternator.
 
http://www.poca.com/index.php/gallery/?g2_itemId=38009
 
Scope trace of the spike for the EE's in the group (It's just as Tomas suggested)
 
http://www.poca.com/index.php/gallery/?g2_itemId=38014
 
 
You might also find this interesting.   I was surprised what the factory did to connect the ammeter circuit to the alternator circuit. 
 
http://www.poca.com/index.php/gallery/?g2_itemId=38011
 
 
A couple of notes:  I disconnected and connected the battery when 20A was flowing in that circuit.  A fool proof test would do it at 70A, but I'm pretty satisfied. 
 
Given these tests, I will go ahead and put a circuit breaker on the ammeter circuit.  (I have more detail if anyone wants to email me directly) and a 4guage line from the ammeter to the fuse box.   The factory "wire merge" will get replaced with a terminal block.
 
It also looks like a 140A alternator was significant overkill as I'm only consuming about 60A (if the battery is charged), but it has the benefit of having enough juice for lots of stoplight to stoplight putting around town without draining the battery.  I probably could have gotten by with a 100A alt that puts out at least 40A at 800 rpm.
 
David
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