I usually listen to my car audio system with the car parked in the garage and the car ignition turned on. The garage door is open ofcourse.
I usually will listen for about 2 hours continuously with the car always idling, never turned off.
When I first start my listening session, my voltage is at about 13.8 volts. After the 2 hour session, the voltage drops to about 12.8 volts.
Is this normal??? Is this supposed to happen even with the car's ignition always on ???

 

charging voltage tends to drop as the alternator& regulator get hot, this condition is worse with internally regulated alternators.i fixed mine by going external adjustable regulation. [img]graemlins/thumb.gif[/img]

 

Thanks for the reply. Could you please expand on what you said about "externally regulated".

 

you have a regulator built into the alternator, to keep your voltage from getting to high. an "externally regulated" alternator has this regulator outside the casing of the alternator.

 

I know some older alternators waited untill they hit a certain RPM before they turned on ie. 1200 to 1500, this was especially on small cars.

 

It is normal to charge higher when you first start up, your alt is charging the battery back up so it's working harder. I used to start up in the winter after my security system being on for a few days, batt is down a little, I start up and i'm getting up to 14.8 v. I always thought the dash gauge was off but a good shop MultiMeter confirmed this. I have a multimeter installed in the car now and since I switch to a optima yellow top a few weeks ago i'm only charging about 14.1.
Even with the Deep Cycle If i know i'm going to listen for a while i'll put on a charger before I climb in.

 

BTW, an alternator usually generates a good bit more at around 1500-2000rpm than it does at idle. That may be part of the reason why you're having a slow voltage drop, the alternator can't quite keep up at that engine speed.

BTW, I hope you know it's not very good for your engine's bottom end to let it idle excessively. 2 hours is a long time for an engine to idle. [img]graemlins/freak.gif[/img]

 

my alternator went **** up from idling

 

that's because at idle an alternator can't supply as much current as it can when the engine is spinning it at a decent rate so it's harder on the alternator this can cause premature failure.

 

The Mini's alt. won't charge until it's about 1500rpm's. It will in reality use the batt. to run the car. under 1500. It realy likes to charge 2-4000rpm's. During an show I can get about 3hrs on an moderate vollume I like Bootleg run an yellow top and run an extra charge before an show. I just had the yellow top serviced at the local yellow top dealer and I had ? them on the right and wrongs, they said that the way I have been doing it is the right way and thats how the batt ( yellow top ) was made to work. Thus just an good charge was needed. The yellow top has been in service for about 4yrs. So must be doing somthing right.