alternator output/Optima battery

[chpr1972]

I just had my SI Vintage Air alternator checked and it is putting out 100 amps and 14.8 volts. Do I need to replace the regulator with a higher volt regulator to 15/2? If so who makes one that will work correctly. My Optima battery charged up to 12.36 volts and my junk charger says it is charged. Local parts house says it is good. I know that Optima batteries are not the same as regular batteries so is this right?

[TheJDMan]

100 amps 14.8 volts is perfect, sounds like you are golden. Why would you think there is something that needs to be changed?

[ccmc]

And what is your idle speed? My LS1 idled so low in gear, 550, that the alternator was barely charging. I swapped an overdrive pulley, smaller one, on so the alternator put out more at my low cruising rpm. I'm usually at 1200 1800 to rpms.

Rick

[chpr1972]

had a problem and battery ran down. just thought that 15.2 would be better. I have dual fans HP EFI, aftermarket headlites Retrosound radio that maybee sometime I will add a 200? ers oamp and Vintage Air. Coming home from Daytona across the dark forest last year I was running in rain with wipers on, radio on,heater on, headlites on bright and it did not crank over next morning enought to start. I sent the one wire alt to Tuff Stuff and they modified it for a 3 wire. I will check the amp at idle when I get the HP EFI back from Holly. Just running gremlins and omitting potential problems. Thanks

[ccmc]

I would definitely look into a higher amp output alternator, but they tend to put out less at idle than a lower output one so I would also replace the pulley with an overdrive one, smaller pulley. You can also see if an suv or big truck alternator will fit your engine, they tend to be 150 to 200 amps

[chpr1972]

It is a Vintage Air front runner system so a pulley change would be a lot of trouble. As soon as I get the car running again I will check alt output at low speed. With tire size 25.5" tall and rear end ratio 3:50/ 9" I run down road at 2200 rpm at about 65 mph in 5th gear[ TKO600]

[TheJDMan]

Idle rpm and pulley size are not likely an issue if you were driving and the battery was still dead the next morning. Most likely issue is that 100 amp is simply not sufficient for all your electrical load. Also, I'm not a fan of one wire alternators but it is a simple matter to convert a 10SI or 12SI alt to a three wire configuration. You may need to move up to a 140amp or even a 200amp alternator to keep up with the load and still charge the battery. It is also possible that the way you have the car wired is creating a voltage drop and is not commanding the full output of the alt. I would recommend that you spend some time learning about charging systems. Mad Electrical has some great technical pages which explain how a typical charging system works and how to optimize them.

http://madelectrical.com/electrical-tech.shtml

[chpr1972]

It is 3 wire alt putting out 14.8 v and 100 amps. The problem was a stuck convertable top switch. Do not know why it did not make noise when I shut the car off. I was having a starting problem that turned out to be a distributor module.