How many amps is our alternator?
- Thread starter jtoddk98
- Start date
Enjoy the results!Usually the scenario means the alternator is not putting out enough current. You had headlights and ac on at the time though, right? How is it at cruise/higher rpm? Alternator output is minimal at idle. Like BiGMaC said, higher capacity battery will help. Did you have the battery replaced recently?
power is coming direct from the battery, 4Ga wire and a big 2ga ground. The battery was replaced back in March 2014 with a Ford Motorcraft battery 650cca. so it's not that old. At cruise, voltage is good, no dimming. It's mainly at idle.SHOdded said:
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If you want to investigate further, check current draw with EVERYTHING off, doors closed, key out of ignition etc. Disconnect the negative terminal. Bridge the post and terminal with a multimeter set to read AMPS (multimeter should have a high range/capacity, I usually see 10A spec'd; start with largest AMP setting, work your way down to milliAmps as needed). Ideally, you will have < 50 mA or so "parasitic" draw at this point.
Switch the multimeter back to the highest AMP setting. After that, turn on your audio system and see how much current it draws, in your implementation. Turn off the audio system, then turn on your headlights to get the current draw from that. Then you will have a better idea how much power demand you are putting on the system (except for A/C of course) while idling.
All these tests are without starting the engine.
http://www.d-series.org/forums/665906-post1.html
There are videos on YT also on how to do this.
And just for you: http://www.aa1car.com/library/alternator_highoutput.htm
Switch the multimeter back to the highest AMP setting. After that, turn on your audio system and see how much current it draws, in your implementation. Turn off the audio system, then turn on your headlights to get the current draw from that. Then you will have a better idea how much power demand you are putting on the system (except for A/C of course) while idling.
All these tests are without starting the engine.
http://www.d-series.org/forums/665906-post1.html
There are videos on YT also on how to do this.
And just for you: http://www.aa1car.com/library/alternator_highoutput.htm
I only skimmed a few of the posts so sorry if I repeat something.
Do NOT get an extra 12.6V battery to help with dimming. They are for extended car off play time only. Batteries only supply power when the car is off and are actually an extra load on the charging system once the car is running. After the car starts its all on the alternator for providing power unless you max out the current capacity of the alt and/or its wiring. If you're voltage goes below 12.6 with the car running you're maxing out the alternator and you'll burn it up in short order with the battery and starter following right behind. Only under 12.6V with the car running are you using any output from the battery.
Alternators, even a lot of high current ones, suck at idle. The easiest advice would be to just turn it down then. Incandescent lights dim when the voltage goes down. The voltage goes down when the alternator can't supply enough current at 14.4V to meet demand. Bigger wires to the amp or amp ground won't stop the dimming because the amp is already pulling more current then the alternator (or its power connections) can supply at 14.4.
Have you done the "big 3" upgrade? They're very important and can't be overlooked. Most stock wiring just has a tiny 10 or 8 awg ground strap going from the engine block to the frame. You need to make sure you can get all the current out of the alternator with as little restriction possible. You'll need to run a heavy ground from (usually) the alternator's mounting bolt to a very good chassis ground, the same gauge wire from that chassis ground to the negative battery terminal, and the same gauge wire from the alternator's positive post to the battery (replacing stock cable).
People will argue about them but I think stiffening caps can help in limited situations though you would need a big amount of storage in them. They charge at the voltage of the alternator and release current at that same voltage so it can help. But they can only supply power for very short bursts (unless you have HUGE banks) and once that power is gone they're another load until it quickly charges back up. Well designed amps should already have enough caps in them to work well on a properly working charging system.
Do NOT get an extra 12.6V battery to help with dimming. They are for extended car off play time only. Batteries only supply power when the car is off and are actually an extra load on the charging system once the car is running. After the car starts its all on the alternator for providing power unless you max out the current capacity of the alt and/or its wiring. If you're voltage goes below 12.6 with the car running you're maxing out the alternator and you'll burn it up in short order with the battery and starter following right behind. Only under 12.6V with the car running are you using any output from the battery.
Alternators, even a lot of high current ones, suck at idle. The easiest advice would be to just turn it down then. Incandescent lights dim when the voltage goes down. The voltage goes down when the alternator can't supply enough current at 14.4V to meet demand. Bigger wires to the amp or amp ground won't stop the dimming because the amp is already pulling more current then the alternator (or its power connections) can supply at 14.4.
Have you done the "big 3" upgrade? They're very important and can't be overlooked. Most stock wiring just has a tiny 10 or 8 awg ground strap going from the engine block to the frame. You need to make sure you can get all the current out of the alternator with as little restriction possible. You'll need to run a heavy ground from (usually) the alternator's mounting bolt to a very good chassis ground, the same gauge wire from that chassis ground to the negative battery terminal, and the same gauge wire from the alternator's positive post to the battery (replacing stock cable).
People will argue about them but I think stiffening caps can help in limited situations though you would need a big amount of storage in them. They charge at the voltage of the alternator and release current at that same voltage so it can help. But they can only supply power for very short bursts (unless you have HUGE banks) and once that power is gone they're another load until it quickly charges back up. Well designed amps should already have enough caps in them to work well on a properly working charging system.
