47 2 Door Coupe Posted August 22, 2013 Report Share Posted August 22, 2013 ANYBODY- Can we use the original 1946-'48 P-15 35 amp gauge with a 1980 60 amp alternator? Looks like it's hefty enough to take the amp spikes? Otherwise I'll have to use/swap out the guts from a 60 amp gauge and that's a lot of work... Thanks!! '47 2 Door Coupe Quote Link to comment Share on other sites More sharing options...
TodFitch Posted August 22, 2013 Report Share Posted August 22, 2013 There is a reasonable chance that you won't actually be having the alternator dump all 60 amps into the battery which is what the ammeter measures so you might get away with it. OTOH, you could also put an external shunt on the ammeter to bring the current going through the ammeter into its designed range. Quote Link to comment Share on other sites More sharing options...
Don Coatney Posted August 22, 2013 Report Share Posted August 22, 2013 As Tod said the internal regulator in the alternator will only put out what the system is calling for. But I must ask why you need a 60 amp alternator? What electric devices are you using that require that much current? Quote Link to comment Share on other sites More sharing options...
TodFitch Posted August 22, 2013 Report Share Posted August 22, 2013 Back of the napkin: Assume you don't want more that 0.1 volt drop between the alternator and the battery (so the regulator in the alternator actually "sees" something close to the battery voltage). At 60 amps you want less than V/R ohms loss (about 0.002 ohms). Further assume the distance from the alternator to the dash and back to the battery requires about 10' of wire. Looking at the calculator at http://www.cirris.com/testing/resistance/wire.html it looks like you'll need AWG4 wire. Are you replacing all the wiring too or keeping the stock AWG 10 wire? The stock AWG 10 wire, for that length will have about 0.01 ohms resistance or a voltage drop of 0.6 at 60 amps. Quote Link to comment Share on other sites More sharing options...
Merle Coggins Posted August 22, 2013 Report Share Posted August 22, 2013 But I must ask why you need a 60 amp alternator? What electric devices are you using that require that much current? I'm guessing it the same reason why you "needed" more horsepower from your engine. 1 Quote Link to comment Share on other sites More sharing options...
Plymouthy Adams Posted August 22, 2013 Report Share Posted August 22, 2013 odds are the 60 may well be the lowest output alternator he can find..most today hover in the 90 AMP output area..explore shunts Quote Link to comment Share on other sites More sharing options...
Don Coatney Posted August 22, 2013 Report Share Posted August 22, 2013 I was thinking my GM alternator is a 30 amp unit but it has been several years and my memory fades faster than my alternator output. Quote Link to comment Share on other sites More sharing options...
glasspacks Posted January 6, 2014 Report Share Posted January 6, 2014 Your 60 AMP alternator may be a little over kill for your application. In my 1941 Fargo I installed a GM 45 AMP ( if memory serves ) everyting is on 12 volts and been working that way for years. Bob. Quote Link to comment Share on other sites More sharing options...
47 2 Door Coupe Posted October 21, 2014 Author Report Share Posted October 21, 2014 An FYI Update- We went ahead and took a chance and used the original 1980 225 CI alternator that is rated at 60 amps since writing our original post and are proud to say that we haven't had any issues thus far... Quote Link to comment Share on other sites More sharing options...
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