I seem to be having a problem keeping a good charge....
I am running the following electrical accessories:
MSD6AL
Jacobs Nitrous Mastermind
Holley Electric fuel pump
Dual Spal Elec. fans
All of these run continuously....and then I sometimes use the headlights and radio....

But using the fans, msd, nitrous box, and fuel pump can sometimes drain my battery dead if i idle too long. I think the kicker is the electric fans running though.

In any case, I have a 100amp alternator which I would think is plenty....and when I am over idle, the car will charge according to the amp meter. The only things that I think can be the problem is the battery or my pulleys....I do have the underdrive pulleys, but I thought the alternator pulley was larger than teh original to compensate the slower RPM of the belt. Im just not sure though....
What do you all think might be bad....battery not taking a good charge or the pulley not big enough? I would think the 100amp alternator is big enough though?

Thanks!
Chris

 

It is not unusual at all for High output alternators to have LOWER output at idle - most are this way. I am not surprised. I have recently seen ads for high output that also have a high output at idle, but I don't remember where - sorry.

And by the way, if the alternator pulley is LARGER, then it will turn SLOWER. That is probably also contributing to your problem.



[Modified by pws69, 5:05 PM 6/29/2003]

 

Thanks pws....im not gonna change my alternator cause its brand spankin' new....but im gonna see if my old alternator has a smaller pulley then since the smaller the faster it spins.
Appreciate your help.....anyone think this could be battery related??

 

OK, first off, you are running a TON of electrical gear there and it's going to take something over 100 amps MY 108 amp with ONE cooling fan is what I consider marginal and I have a stock type TPI and just ONE cooling fan...
with nothing unusual in loading after that....

I know the newer alternators have a supposedly higher output rating, but truth is they can't do it...not for long...not enough airflow through the unit given the demands.....and the ambient under the hood temps off a V8 with headers....just aint'a gonna happen on a reliable basis....

SO it seems histerically from what I have found the only option is a SI17 series alternator, found on say Caddy sevilles of say 79 vintage...
NOW this is the same 2 wire regulator, white plastic inline plug you shoud have now....so it's directly interchangeabel....but the diameter of the alt is slightly bigger....
pulleys and such crap excepted...yougot to see the belts line up...use a metal straight edge over the pully faces to see this happens....

NOW this series of alternators is possible to be upgraded to a 'hotrod' alternator of much higher output ratings....but make NO mistake about it, this larger diameter more airflow alternator is a superior design to the later model things with NO serious long term output....

GENE

 

After I installed the dual Spals on my 82 the voltage dropped low at idle frequently with a 100 amp alternator. I bought some of the heavy power amp wire (6 gauge I think) from Radio Shack. I ran one line from the alternator output to my accessory panel. A second line was added between the ground and the frame. I noticed the difference immediately.

Dane

 

Just the products themselves doesn't tell me enough to work out the power requirements. You need to look at the wattage or amperage on the units and calculate whether the system will provide enough power. And, yes at idle the output of your alternator will be low...probably only 30amps for a high output unit. Standard units only put out about 15amps at idle as I recall. A smaller pulley will help a great deal. You might also want to get a deep cycle battery like the nautalis units availabe at Kragen/Checker/Schucks...they take a lot of punishment like drain all the way down and quick charged back up without damaging the battery...good for vettes which sit in the garage over the winter.

 

I threw on that smaller pulley and it chages a lot more now, even with the fans running....
IM gonna check into that deep cycle battery like RockNRoll suggested.
Thanks guys