2nd stock dedicated alt. vs. 1 aftermarket alt.

[speedracerx 10+ year member]

I've finally pretty much excepted the fact that I should run two batteries, but still don't wanna cause adding weight every year to a hot rod goes against a gearheads core programming. I already have the audio system's wiring circuit completely isolated to eliminate any ground variance. That being considered, as well as the fact that I have a dozen stock alternators laying around, would just adding a isolated 100 amp GM alternator be comparable to replacing the single factory one with a quality hi amp alternator? Would the premium single alternator allow me to stay with a single battery? I can work the numbers but some educated opinions would be appreciated.

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[audiolife 5,000+ posts]

its pretty simple concept start plugging in figures like what your alts put out at idle and what the system can draw. way too many times i see electrical systems discribed like a switch oddly enough they are not....not only that it takes horse power to make electrical power..i think that would mean more than 60-70 lbs..

 

[speedracerx 10+ year member]

My logic is fuzzy on occasion, but I'm thinking 50 lbs is 50 lbs, unless you pull over and remove the battery, then drive off without it. I figure its easier to turn the volume down, or turn off the a.c and fan when I need all my 509 ci engine has got. I believe it requires about 5 h.p. to "excite the field", beyond that I have always understood the load is proportional to what its powering (your switch analogy?). I figure the common case of alt belt slippage only when the headlights are on might justify this, but again I often truly do have fuzzy logic. One consideration I have no answer to is whether the effects of having the cleaner (quieter) output of a high quality alternator can be realized enough to justify it over a cheaper way getting just the extra power output capacity. I have no audible "before and after"experience with aftermarket alternators where output was equal. If I'm in left field here, please let me know.

 

[audiolife 5,000+ posts]

5 hp to do a 200 amp load? and my switch analogy is simple your car electrical isnt a switch. takes mechanical power to make electrical power. ........

 

[NewToTheGrounds 10+ year member]

a cap won't help, just curios ?

 

[speedracerx 10+ year member]

So you are saying if you have a 200 amp alternator, you have a 200 amp load, period, and no matter if the "switch" is turned off (headlights, blower motor, 4000 watt amp., etc) that tells the alternator's regulator "need more power"(hence the name...regulator) that your still cranking out 200 amps? I know I'm missing your point cause I know that cant be what you are saying, the power has to go somewhere. Heat is one place, but not 150 unneeded amps worth. I have an article on how to wire an "off switch" that kills the alternator. Drag cars do it sometimes so they are charging during the burnout but not down the track. You have to take the field power away so it's more than just a switch. I'll just except that you are telling me high amp alternators take more power to spin, even in a low output situation, than lower capacity alternators do. Sorry I cant follow you, but thanks for trying.

 

[speedracerx 10+ year member]

Oh yea, I was saying 5hp just to excite the field, or turn alt. "on" so you're not just using battery power. This comment is wrong though,rpms and a few seconds of battery power excite the field so it's a bogus point.