Martingale

Okay, the stock LS1 Alternator is 105 amps, right?

Based on the assumption that alternators usually have a 40%
reserve capacity, 105 X .4 = 42 amp reserve capacity.

All of your amps and their fuse ratings should add up to a max of around 85-90 peak amps. If you take half of 90 and it puts you around 42-45 RMS amp draw...so your amps shouldn't draw any more then 90 peak amps, is that correct? Someone correct me if I'm wrong.

Basically I wanted to run a 55x4 Alpine amp and a 550x1 Hifonics amp for the subs but my buddy said that would take way too much of a draw. He suggested a 40x4 Alpine amp that uses one 25 amp fuse, then a 400x1 Alpine amp that uses two 30 amp fuses. This is 25 + 30 + 30 = 85 peak amp draw that would equal 42.5 amps RMS, basically a tad over 40% of the alternators total capacity. He said that's all I should run and not take any more of a draw. Is this correct? Someone tell me if I'm we're wrong here. I'd like to run the 550x1 Hifonics amp but not at the expense if draining the electrical system. Thanks.

2FAST4U

First I will say you are fine with those amps.

Now as far as your math Wrong. See you have to see at what RPM the alternator is at to give 105 and then at idel what the amps are a that is the X. or if you always plan on reving the motor none stop at traffic lights?

Martingale

Okay, I understand what your point about the alternators output at idle versus while the motor is revving. Now I will be fine with what two amps, the 55x4 and 550x1 combo or the 40x4 and 400x1 combo? I assume you're speaking of the second because that's the one I have the fuse numbers for (25 + 30 + 30 = 85).

Now...if the alternator puts out less then 105 amps at idle, then those two amps with the 42.5 RMS (85 peak) amp draw would take more then 40% of its capacity at idle. Does an alternator have more of a reserve capacity to spare then 40% or is my math to come to the conclusion of 42.5 RMS amps wrong?

If someone can make this easy can you just tell me the total amount of amps I can draw? What can I get away with...a 25 amp fuse on one amp and two 30's on another? More? What's the limit here. Thanks.

00whitels1

if you are worried about draw save yourself the math and buy a capacitor. stinger makes some really good caps (stingerelectronics.com) you could def. get away with one of the super capacitors that are 1 farad or play it really safe and get the bigger one that is 3 farads........they usually help alot and you don't have to worry about much of the amps being drawn off the altenator. my friend has a 1000 watt mono amp and a 600x4 powering his interiors and his box and he has a 1 farad cap. thats taking care of all of his power drawing problems.

2MuchRiceMakesMeSick

The question "how much amperage draw will your ls1 alternator take?" is simple. 105 amps. Basically if you draw over 105 amps, your amp will rely on your battery to produce it. If it cant produce it then the signal is clipped and your wattage goes down while heat goes up. Heat is the #1 most common reason for electronic failure. The usage of a capacitor (1F for every 1000wrms) will help with your immediate draw but is not a solution to the root of the problem which would be your alt.

With that in mind, you should be fine with the amps you have selected.

Dal1as

Unless you're running around playing sinewaves at full blast I wouldn't worry about a new alternator or a cap unless you're well over 1000 watts or have very inneficient amps.

I am running the following amps and have had no problem at all. Not even light dimming.

Diamond Audio D5 600.2 150x2 RMS (regulated)
Diamond Audio D5 1200.1 900x1 RMS (regulated)

I did the big 3 and dropped in an Optima Yellow top, also paying particular attention to where I grounded my amps. I have had no problems and can play my stereo at a decent level for over an hour with the engine off. Alot of factors play into this but with the two amps you listed you should be fine. Go ahead and do the big 3 and possibly invest in a yellowtop if you like playing your car stereo with the engine off. Don't waste you're money on a cap.

I forgot to mention that I'm running an ASP underdrive pulley also.

ultraz

iTrader: (4)

i wouldnt reccommend NOT using a capacitor, even IF u had a 180 amp alternator. AMplifiers will always benefit from a capacitor, even if no significant voltage drop can be seen. A capacitor will hold a reserve power especially for when the bass hits, which will mean ur amp is getting all the power it wants. Without a capacitor, it would be near impossible to power a subwoofer to its full potential wihtout using a crazy thick power wire.

Richiec77

iTrader: (3)

RMS is only used for measuring the "Root Mean Square" of a sinusoidal wave form. So to get an Algebraic equivialent of a DC signal you measure Peak by 0.707 to attain the
RMS of the Voltage

Current could be measured in RMS but Average is a more usable formula. All you need to know is that music is dynamic in nature and doesn't consume in a continuous fashion. So 40% is just somebodies Opinion of what the Alt should run at.

Figure you need to concentate on upgrading the Ground and Power wires in the car now before you should concern yourself about your alternator. (factory Wires)

I'm still trying to sort out what your measurements are a dirivitive of???

2MuchRiceMakesMeSick

Actually this depends on what kind of amps you use. Some amps now have built in caps.

Okie5.3

iTrader: (1)

IMHO. to calculate the current (I) draw of the amp (assuming peak power) when voltage (E) and power (W) are known, use the following - I = W / E. 220w(55x4)/13vdc=17a. this is using a nominal 13vdc with the amp at peak power. and since this was calculated at peak power your RMS, or average power will be significantly less. as the voltage increases your current draw will decrease, so at an idle you will have a higher current draw for the same amount of power (sound) than at cruising speed.

Dal1as

Exactly. When I got my amps I took them apart to make sure the circuit boards were correct (Don't trust the internet. lol) and I noticed the caps. From what I've read and seen most decent amps use more than enough capaciters to filter the power entering the amp.

Richiec77

iTrader: (3)

Correct. Most Reputable Amplifiers have plenty of Capacity built into them to handle the Filtration issues. This has to be done due to the More "dirty" power comming into them. Todays cars with EFI has a lot more switching going on due to the Plethora of sensors. So the DC voltage starts to have a lot more spikes. The job of the Power supply filtering is to have roughly 20% reserve to handle most Transient.


But todays higher than normal Demands, and the common Missuse of the Amplifiers gains allows Clipped signal to happen. These signals Strain the Amplifiers Power Supply to the Point that Voltage will Drop due to the increase in Resistance from Heat. A cascading effect. So external Capacity helps prevent other Car items from fighting for the rest of the Current available.

In Short, All cars will do better with some form of external Capacitor.


Here is some info and graphs. Also remember to make it totally real world you would have to add in all the other "Noises"

http://www.rockfordfosgate.com/scrip...Z2U9MQ**&p_li=

iosigma

I can attest to the issue of using a cap. I ran to JL Audio 10's off an INfinity Kappa 102A and a Sony 4 Channel running the other speakers.( MB Quart) This was in my jeep. The HU was Clarion. UNtil I added a cap the Alternator would whine and so forth. I guess from the load of everything running as well as the stereo. Added a cap and things were great!

Christos

I've always read a cap is a waste of money, and at best, only works for 1/1000th of a second.

Although on that note, the 50+ farad battcaps I have heard work well, since they have enough farads.

On that note, how will adding a cap, something which drains additional power from your car, benifit you?

Richiec77

iTrader: (3)

I love the BattCaps. They are the Best For SPL.

No. The Size of the Capcitor will determine it's discharge rate. It is a waste of money if a Size too small is used. They are also a bad idea to be used in SPL unless you get into 50+ farad amounts.

If the capictor is too small, It becomes a load itself, and starts fighting for current. Once it discharges, it then need to rechrarge. SO if you are running Test Tones, you will drain a cap quickly. For normal listening, A couple of Farads will help. This is truely a case of More is Better.

2MuchRiceMakesMeSick

Caps act as a quick battery for when your battery cannot discharge fast enough. If you cant get the power to your amp, the signal will clip and your amp will heat up. Eventually it will cause coponent failure. They are suppost to discharge fast, they just spot the battery when your amp needs that extra amperage. They are not a wastse of money at all when you get into higher wattage amps

Dal1as

I also forgot that my amps have regulated power supplies which in most cases would not benefit from caps. So I guess a powerful enough system with unregulated power supplies would benefit from a cap.

Hell I can sit at an idle and pound away and no light dimmage at all. Meaning that my amps are not pulling more current than the battery can handle, because if they were it would begin to draw from the rest of the system dimming lights and such. At least that sounds right. I may be wrong.

2MuchRiceMakesMeSick

Regulated ps means that the voltage is always the same voltage.
Remember amperage and voltage are two different things here.
No matter what the voltage, your battery can only discharge (measured in amps)
so quickly, and thats why we have caps.

Dal1as

Got ya. Then am I right that lights dimming is a sign of this?

2MuchRiceMakesMeSick

Yes you are but once your amperage draw exceeds the amount your battery can discharge then your electrical system will suffer as a result. Its quite possible that your amps have built in caps. (all amps have capacitors, they are used in many ways, but yours may have them for power discharge reasons). What kind of amps are they?