Higher amperage alt question
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Post Fiend
Joined: Jul 2005
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From: Durant, OK (SOSU)
Higher amperage alt question
Ok I've wondered this for a while. My alt works great once I'm moving...but sometimes I need to sit at idle with ALL of my lights on and it's taking a hit on my battery.
Higher amperage alternators obviously put out more amps when running...but will they put out more amperage at idle as well, when stock alts can't put out their rated amperage?
I've put two higher amperage alts in a Chevy and GMC in the last few years, but upgraded the battery at the same time, so I'm not sure if the idle output went up.
So...does the idle output get higher with a higher amperage alternator? Thanks in advance.
Higher amperage alternators obviously put out more amps when running...but will they put out more amperage at idle as well, when stock alts can't put out their rated amperage?
I've put two higher amperage alts in a Chevy and GMC in the last few years, but upgraded the battery at the same time, so I'm not sure if the idle output went up.
So...does the idle output get higher with a higher amperage alternator? Thanks in advance.
Posting Legend
Joined: Sep 2001
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So how many lights are you running? How long are you idling?
The stock alt should work fine for a stock vehicle.
Have your alternator checked by a shop. It may have some diodes out.
A higher amp alternator is capable of higher amps but whether it produces the amps is determined by load and the regulator. A smaller pulley may work as well as a bigger alternator.
The stock alt should work fine for a stock vehicle.
Have your alternator checked by a shop. It may have some diodes out.
A higher amp alternator is capable of higher amps but whether it produces the amps is determined by load and the regulator. A smaller pulley may work as well as a bigger alternator.
New User
Joined: Jan 2008
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Most charging systems (Voltage Regulator) don't kick in until 850-900 RPM.
It's the VR that gets the charge going.
For Headlights.
Do the relay upgrade and run the headlights off battery power instead.
That will take some strain of the VR/Alt
http://www.northwestvintagebroncos.c...headlight1.htm
It's the VR that gets the charge going.
For Headlights.
Do the relay upgrade and run the headlights off battery power instead.
That will take some strain of the VR/Alt
http://www.northwestvintagebroncos.c...headlight1.htm
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Post Fiend
Joined: Jul 2005
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From: Durant, OK (SOSU)
The headlights aren't the problem, they still run good and bright. I will do that upgrade as soon as I get the chance however.
I have two 3.5" driving lights and two 2" fog lights. The driving lights are 100W each, fogs are 85W each. Both are run on 30 amp fuses, so they are obviously pulling less than that individually. In addition, with the radio at a mid-volume, and the lights on, the main fuse I have (100 amp) doesn't blow, so altogether those accessories are pulling less than 100 amps.
The lights don't dim or anything...just the voltmeter in the dash (I know...I know...peice of crap) drops some when I turn the lights on. Even with the volume up high and the sub hitting hard, the lights don't dim when the sub goes off.
Perhaps I'll just figure out a way to install some sort of high-idle mod to set the idle around 1K or so when I need it.
Thanks for the help both of you, and the link Mil1ion.
I have two 3.5" driving lights and two 2" fog lights. The driving lights are 100W each, fogs are 85W each. Both are run on 30 amp fuses, so they are obviously pulling less than that individually. In addition, with the radio at a mid-volume, and the lights on, the main fuse I have (100 amp) doesn't blow, so altogether those accessories are pulling less than 100 amps.
The lights don't dim or anything...just the voltmeter in the dash (I know...I know...peice of crap) drops some when I turn the lights on. Even with the volume up high and the sub hitting hard, the lights don't dim when the sub goes off.
Perhaps I'll just figure out a way to install some sort of high-idle mod to set the idle around 1K or so when I need it.
Thanks for the help both of you, and the link Mil1ion.
Elder User
Joined: Jan 2007
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Most high output alternators actually put out LESS current at idle the most stock alternators. They only put out more current at higher RPM levels. You can put a smaller pulley on the alternator so it spins faster. That should get rid of your problem.
Elder User
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Originally Posted by Mil1ion
Most charging systems (Voltage Regulator) don't kick in until 850-900 RPM.
Regulators have no way of knowing how fast the alternator is spinning at or even if the alternator is spinning at all. A regulator will function if its not even hooked up to an alternator.
You get dim at idle because the alternator cant put out as much current at idle so the voltage of the electrical system drops.
Elder User
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Originally Posted by Mil1ion
Do the relay upgrade and run the headlights off battery power instead.
That will take some strain of the VR/Alt
Originally Posted by Mil1ion
It does not matter if you hook up a load to the battery, to the ignition circuit, to the ACC circuit or to your tail lights. The load will still present itself on the alternator. The alternator will still need to provide enough current to offset this load. 100% of the vehicles electricity is produced by the alternator. So regardless of where your load is connected it comes back to the alternator. Hooking something directly to the battery versus the ignition circuit is not going to lighten up the load on the alternator. Think about it. Where is the input of the ignition circuit connected to? It connects to the battery like every single other circuit in the vehicle. All circuits eventually lead to the battery and alternator.
And btw that relay upgrade is a rip off. If I were to do that myself it would cost me about $8. All you need is two SPDT 30/40 amp $2 relays amp and some 12 or 10 AWG wire with some 18 AWG wire to connect to the headlight switch.
Last edited by SPL Tech; Mar 26, 2007 at 01:17 AM.
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From: Virginia
Don't panic because the voltmeter is dropping a little bit. The voltage dropping a little bit under load is ok as long as you do not have any other problems.
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Post Fiend
Joined: Jul 2005
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From: Durant, OK (SOSU)
Ok well I have no other problems. I'd consider an alternator pulley swap, but the pulley seems tiny already (it's a stock Ranger one though), and I don't want to overspeed it if I take the engine up to 4500 RPMs or so, which I do once or twice a day on average.
Sorry for the stupid electrical questions, it's one of the things I tend to avoid on my truck and vehicles in general, but I have removed and replaced several alts and I stayed at a Holiday Inn Express in Arizona!
Sorry for the stupid electrical questions, it's one of the things I tend to avoid on my truck and vehicles in general, but I have removed and replaced several alts and I stayed at a Holiday Inn Express in Arizona!
