I'm driving along yesterday and I pull in to get some gas. After I fill up, I go to start the car and I have nothing...no lights on the dash, no interior, motor won't even crank. I jump it with a jump pack and it starts right up. Go to pick up my friend and just out of curiosity, decide to pop start it. I'm doing about 40 MPH at the time, shut the car down, turn it back on...I have nothing again. Put it into gear, let off the clutch and it won't pop start I was right in front of Pep Boys at the time so I run in, buy a jump pack, hook it up, and it starts fine. Headlights stay on, but my VAFC2 and my radio won't come on. I couldn't get an accurate reading on the battery from my meter, but I'm guessing its the alternator or do you guys think its my Battery (yellow top about 6 moths old)

I do have a stereo in the car and it draws a sh1tload when its cranked up. If you guys think its the alternator....what aftermarket ones are you running. I need to get this car running again ASAP cause its my daily driver. Thanks for the help

 

To do a simple test on the alt. start the car, disconnect the batt. if the car keeps running, the alt. is working, it does not mean it's working properly, only that it's working, you can also go to just about any batt./alt. shop and have them to a check, most do not charge for this, it only takes a min.

Also how much RMS wattage are you running? 94

 

I'm running about 3000 watts (conservative number) on just the sub amps

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Speed94 &raquo;</TD></TR><TR><TD CLASS="quote">I'm running about 3000 watts (conservative number) on just the sub amps</TD></TR></TABLE> Is that RMS watts? What is the brand and model of the amps?

If it is RMS watts, I would definitely get the biggest alt. available 94

 

Thats not RMS...I can only get a 150 amp till the belt starts to slip

 

Well thats about 250% better then stock.
What is the RMS watts? 94

 

I think RMS is like 300-600 at 4 Ohms

 

At 300W RMS you would not need an upgraded alt. even a 600W You really don't need one although going to a 75A-100A can't hurt, don't forget because music is dynamic the amount of power the amp needs is constantly changing and even if you have the system cranked you war only producing 600W RMS for probably less then 50% of the time, you need about 95A to make 600W of RMS power so you can see that before a lack of current becomes a problem you would have to be driving around with the tunes cranked all the time.

With that said, if the alt. needs replacing, it sure can't hurt to upgrade it , and how "big" an alt. you go with will depend on two main things, what are you maybe thinking about doing in the future with the sound system and how much money do you have burning a hole in your pocket right now. 94

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fcm &raquo;</TD></TR><TR><TD CLASS="quote">At 300W RMS you would not need an upgraded alt. even a 600W You really don't need one although going to a 75A-100A can't hurt, don't forget because music is dynamic the amount of power the amp needs is constantly changing and even if you have the system cranked you war only producing 600W RMS for probably less then 50% of the time, you need about 95A to make 600W of RMS power so you can see that before a lack of current becomes a problem you would have to be driving around with the tunes cranked all the time.

With that said, if the alt. needs replacing, it sure can't hurt to upgrade it , and how "big" an alt. you go with will depend on two main things, what are you maybe thinking about doing in the future with the sound system and how much money do you have burning a hole in your pocket right now. 94 </TD></TR></TABLE>

I think you're forgetting that I am running 2 of those amps When I do play them at full volume (once in a blue moon while driving) my light dim when the bass hits to the point of them almost not being on. I run a 30 farad cap also It was the battery that took a crap. I checked it at my friends shop with the load tester. At idle with everything on it was reading 13.8. Shut the car off and it read around 8 volts. Put a load to it and it shut off the machine lol. Got a new cheap battery and its working fine now. Its the first Yellow top I've ever had a problem with. I have 5 in my truck for almost 4 years now and no problems with any of them

 

A 30 farad cap? Maybe thats what took out the yellow top, should be about 1 farad per 500W RMS.
What is/are the makes and models of the amps? 94

 

kicker kx 1200...let me know when the book comes out

 

The KX1200.1, [300W RMS into 4 ohms @ 14.4V] And you have 2 of them, running what? 94

 

2 memphis mojo 12's

 

4 ohm loads? 94

 

Yep...thats all they sell them as

 

OK, then the max RMS wattage is 600W @ 14.4V and the max current draw would be about 95A for the 2 amps, a 1 farad cap, [2 farads at the most] should be all you need, using a 30 farad cap is just putting an unnecessary load on the charging system.
If you are getting the extreme dimming you say you were when cranking the system, I would be looking for another problem, maybe wiring, [power or grounds] 600W RMS should not be causing that kind of dimming unless there is something else wrong. 94

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fcm &raquo;</TD></TR><TR><TD CLASS="quote">you need about 95A to make 600W of RMS power </TD></TR></TABLE>

Im comming up with about 42 amps for 600W at 14.4v

W = V*A
600 = 14.4 * Amps
600/14.4 = Amps
Amps = 41.6666 = 42

I know its not exact with the amplifier counting in the power wasted but i dont think it would be wasting that much

 

I'm just quoting 12volt.com "Current Draw by Power" chart... http://www.the12volt.com/info/recwirsz.asp 94

 

o ok, i was just checking. now i see where they get the 95amps from. They have them rated at 50%efficient, that seems like a really low efficiency for an amplifier to have.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fcm &raquo;</TD></TR><TR><TD CLASS="quote"> A 30 farad cap? Maybe thats what took out the yellow top, should be about 1 farad per 500W RMS.
What is/are the makes and models of the amps? 94</TD></TR></TABLE>

A 30 Farad cap will not take out an alternator.

Cap load (power dissapated by cap)= Current * ESR^2 of cap= very small load

A cap only stores power its like a big bucket of water with a very small hole in the bottom. If your cap is drawing large amounts of current then you have a defective cap.

On a side note: I haven't kept up with extremely large capacitor technology, but last time I checked these were more 2nd batteries then capacitors. Has this changed?

My guess your alternator bit the farm.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by silentblackhat &raquo;</TD></TR><TR><TD CLASS="quote">o ok, i was just checking. now i see where they get the 95amps from. They have them rated at 50%efficient, that seems like a really low efficiency for an amplifier to have. </TD></TR></TABLE>

50% is actually high for class AB design more like 35%-40% where do you think the heat comes from? That is wasted energy.

If its a class D its usually around 75-90% efficient that is why they run a lot cooler. Less wasted energy.

But dont think class D is superior because its not!!!!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nsxxtreme &raquo;</TD></TR><TR><TD CLASS="quote">My guess your alternator bit the farm.</TD></TR></TABLE> It turns out it was his yellow top that went west and the alt. is still working, [he replaced the batt. and says everything is OK now.
I was just wondering why with only 600W RMS he was getting so much dimming of the lights, maybe as you say there is something wrong with the cap. 94

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fcm &raquo;</TD></TR><TR><TD CLASS="quote"> It turns out it was his yellow top that went west and the alt. is still working, [he replaced the batt. and says everything is OK now.
I was just wondering why with only 600W RMS he was getting so much dimming of the lights, maybe as you say there is something wrong with the cap. 94</TD></TR></TABLE>

Your guess is as good as mine...but its 2 amps..not one and I'm running the amp at 2 ohms. So i guess its 190 amps based on your calculations? Thats also not including the 4 channel, but I don't think it would draw that much (Its 170x4)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nsxxtreme &raquo;</TD></TR><TR><TD CLASS="quote">

A 30 Farad cap will not take out an alternator.

Cap load (power dissapated by cap)= Current * ESR^2 of cap= very small load

A cap only stores power its like a big bucket of water with a very small hole in the bottom. If your cap is drawing large amounts of current then you have a defective cap.

On a side note: I haven't kept up with extremely large capacitor technology, but last time I checked these were more 2nd batteries then capacitors. Has this changed?

My guess your alternator bit the farm.</TD></TR></TABLE>

Alternator was fine...battery took a crap. I have a cap as a backup, but haven't installed the second battery yet.

 

I knew it was 2 amps but I didn't know it was 2 ohms, thats why I asked ... <TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fcm &raquo;</TD></TR><TR><TD CLASS="quote"> 4 ohm loads? 94</TD></TR></TABLE> and you said...<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Speed94 &raquo;</TD></TR><TR><TD CLASS="quote">Yep...thats all they sell them as</TD></TR></TABLE> so that kind of changes things also the fact that you also have a 4ch amp. 94

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fcm &raquo;</TD></TR><TR><TD CLASS="quote"> I knew it was 2 amps but I didn't know it was 2 ohms, thats why I asked ... and you said... so that kind of changes things also the fact that you also have a 4ch amp. 94</TD></TR></TABLE>

4 ohm load speakers that go down to 2 ohms. I don't think anyone would run it at 4 ohms unless their amps couldn't handle 2 ohms. Now I'm just waiting for my optima to come back, but they are on backorder