how much amp wattage can the alternator support

[renx215]

I have an 2009 LE with an HID Kit, about 3000 watts between two amps, 1.5 farad cap and a alarm + remote start kit. How much of a draw can we get from these alternators safely without killing them or putting a strain on them?

[frojoe]

What is the amp rating of your alternator? You need that to figure it out accurately, as well as the efficiency of your amps.

The equation you use is P=VA, where P is power, V is input voltage, and A is input amperes.

So if your amps were 100 percent efficient, P would equal 3000. We will use 14 for the voltage, because it varies between 13.8 and 14.4 volts. So... 3000=14xA ... A=214.3amps.

But amps are not 100 percent efficient, say that very optimistically your getting 70%, which is very, very unlikely. At 70% you will need 4286 watts input to make 3000 watts to your speakers. 4286=14xA..... A=306.1amps.

That is what your need to input to make 3000 watts, and running the other electrical systems plus the HIDs is probably another 20-40 amps. That makes your total around 335 amps, which is nowhere close to what your amp makes. Your battery will try to make up the difference, but it won't be anywhere close. The capacitor doesn't help with a lack of total power, but only with voltage regulator lag, so your short a few hundred amps for your system.

Just fyi, my camry has a 65 amp alternator, so I doubt yours is higher than 85 amps at the most.

Another easy way to find the max draw for your system is to add up all the fuses on all of your amps, and this is the total max power draw. So I have 2 amps. One amp has 2 20amp fuses and the other has two 15 amp fuses. The total max draw for my system is 70 amps, and add around 30 for the other electrical systems in the car, and I have a 100 amp load, but only a 65 watt amp, which explains why my lights dim.

Using the same formula, add up the fuses, multiply this number by 14, and you get the wattage it would produce at 100 percent efficiency. Multiply this by like .6 for class-ab amps or .8 for class-d, and you get what the amp can really produce, and if its rated for higher than this number, than it is lying.

Edit: And after doing that math for you I really hope that your were giving me 3000 watts as rms power, because if you meant total power than all of this meant nothing.

[renx215]

I'm so very sorry frojoe, That was 3000 watts peak. RMS, we are talking more like 1100-1300 watts RMS. and I im sure my 2009 corolla Alternator is 80 amps. Should I be safe?

[frojoe]

well that is a lot closer to what the car could handle, that means you won't be able to get 1100 watts out of it continuously, but for the occasional loud base note you will be fine. But look at your amps and add up the fuses, that is the easiest way to tell. And never go by peak power, its a useless measurement that is only so they can advertise more powerful amps.

[renx215]

Well the fuse to my battery from my system is 100, the one for my HID relay harness is 25, and I'm not sure about the one for my remote start/alarm.

My question is, Will this slowely harm my or wear down my 80 amp alternator?

[frojoe]

I meant the fuses on the amps themselves.

As far as your alternator, yes this will increase wear, when you increase the load on a system like this it always will. It shouldn't make your alternator die in a year or two though, unless there was already something wrong with it. Its just that years down the road, it will have been used more heavily.

One other thing to consider is that you probably don't listen at really high power very often, so if you usually listen at pretty low levels, then you are not putting extra stain on your electrical system except for when you crank it, reducing the overall wear on the alternator.

[toyomoho]

The alt will not blow up. Watch the headlights for flicker on bass notes (draw the most power). If the engine starts running strange or dies at idle (with stereo on) there is a problem.

A capacitor will help somewhat but is not a cure.

[Slaughter]

As mentioned that will put extra wear on your alternator as you are trying to draw more than it can put out. If you listen to your music loud, you may want to look at upgrading to a higher output alternator.

For my system, I currently have a 140amp alt (Stock) and a 120amp max draw from my amplifiers. You could also help improve things by running a wire from your positive output on your alternator to your positive battery terminal, and grounding the negative terminal to the engine and another ground to the chassis. I would recommend using 1/0awg wiring to do so (This is referred to as the big 3)

I'm not a pro on this stuff, but have been researching it heavily as my addiction for car audio has increased

[Jigg007]

If you notice your car has a harder time turning over, then whatever you're running is discharging the battery faster than the alternator can recharge it. Keep in mind alternators are only going to put out a fraction of their power at idle, compared to their nominal rpm (2000~) For instance, most 100A alts put out 35A idle.
HIDs are more efficient than the halogens, so consider that you saved power there.

Also, a capacitor will not help unless you have a noticeable voltage drop across the wiring to the amplifier. Save the money that would be spent on a capacitor and get an Optima Yellow Top or similar. And if there is still a problem, an alternator upgrade.

Alternators are much slower than batteries for available power. Keep in mind that any current draw comes off the battery, the alternator then recharges the battery.

[MrGiggles]

Originally Posted by Slaughter

As mentioned that will put extra wear on your alternator as you are trying to draw more than it can put out. If you listen to your music loud, you may want to look at upgrading to a higher output alternator.

For my system, I currently have a 140amp alt (Stock) and a 120amp max draw from my amplifiers. You could also help improve things by running a wire from your positive output on your alternator to your positive battery terminal, and grounding the negative terminal to the engine and another ground to the chassis. I would recommend using 1/0awg wiring to do so (This is referred to as the big 3)

I'm not a pro on this stuff, but have been researching it heavily as my addiction for car audio has increased

The big 3 is a good idea to do. There are some tutorials on how to do it using google.


Borrow or buy a digital multimeter (15.00) and test your voltage to see how low it dips. If it dips below say 12.5, you should upgrade something.

Stepping up to a better battery up front will help some, and adding an extra battery in the back couldn't hurt much either. Kinetik makes great batteries for audio applications, as well as Deka, Optima, and Stinger. If you do get a battery for the rear of the car, make sure it is sealed. If it has maintenance holes on the top it will release chemicals into the cabin, which isn't good. If you upgrade any more, a new high output alt could be in order. Some good companies are Mechman, Irraggi, Excessive Amperage, and Ohio Generator.

[trunks9_us]

Ok guys I been told by my toyota parts place that our 2009 corolla is a 100 amps someone plz lmk if this is true I been reading its 80 amps everywhere. I believe there the same amps as the scion tc but not positive but I believe there in the hair pin design. I am currently looking into this site about gm alternators fitting on our Toyota check out the site I am going to call them tomorrow http://www.alternatorparts.com/Toyot...lternators.htm If you guys dont understand what a hair pin design design alternator is call or do some research on them there different from circle alternators.