# to much current draw?



## makaveli (Oct 5, 2005)

i was wondering if i needed to upgrade my alternator, as of right now im having no dimming problems, no MIL. At the moment i have a (almost) Full Rockford Fosgate system with the stock electrical componets(ALT, BAT, BIG 3 etc). heres what i have: Alpine CDA-9851 headunit powering (1) RF Punch 301M its specs are: 150X1 @ 4 ohm, 300X2 @ 2 ohm, 900W peak. This is how its rated on the box, @ 2 ohms it is actually putting out around 420W. this is powering a RFP4410 which is 200W RMS/400W max. Also i Have a new P2002(nowhere close to as good as the 2003 models) this is 50X2 @ 4 ohms, 100X2 @ 2 ohms. it actually is putting out 140X2 @ 2 ohms. both of the amps have a 30 amp fuse in a distribution block that connects to a 60amp fuse, about 10 in from the battery, i dont know if this matters, but there you go. now if i have the radio on w/ the car off my battery dies in about 20-30 mins. at rest the battery puts out 12.34V- on it puts out 14.2V and on w/ a load( system full, lights on etc) it puts out 13.90V. ***this was however taking the reading after starting the car for the first time that day, about 2 mins after start. my question is, if i have a 60amp fuse on B+ wire does that mean amps are drawing 60 amps? i thought the alt on a 96 200SX SE was only 70 amps? also when the bass hits the engine tone changes, is this the ALT kicking in(this is ideling)? any info is appreciated


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## sr20dem0n (Mar 19, 2003)

That's a single 4ohm sub, so your 301M is only putting out 150rms, not 300rms
If the P2002 is powering your speakers, they're 4ohm, so it's only putting out 50x2.

250rms won't cause any problems, at all. Even if both amps were fully clipped that's still only 4-500rms, which also shouldn't cause any problems (other than clipping sound like crap and possibly blowing your speakers).

The fuse by your battery has nothing to do with what amps you're using or what they're drawing, it's only purpose is to protect the wire in case of a short. It should be smaller than the maximum current the wire is capable of handling, and larger than the normal draw from your amps (so it doesn't blow under normal conditions), past that it can be whatever size you feel like. It doesn't tell you anything about how much current the amps are drawing, all you know is that if it hasn't blown yet, they're drawing less than 60 amps.

The sound you hear is the alternator loading down the engine, lowering the idle temporarily until the idle controller can react and raise the idle back up.

Your voltages are fine


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## makaveli (Oct 5, 2005)

sr20dem0n said:


> That's a single 4ohm sub, so your 301M is only putting out 150rms, not 300rms
> If the P2002 is powering your speakers, they're 4ohm, so it's only putting out 50x2.
> 
> 250rms won't cause any problems, at all. Even if both amps were fully clipped that's still only 4-500rms, which also shouldn't cause any problems (other than clipping sound like crap and possibly blowing your speakers).
> ...


actually the 301M is RATED 150X1 @ 4 ohms, however the ACTUAL output power is closer to the 200W mark @4 ohm, and if i get another sub, It will be pushing AROUND [email protected] ohms. Also The p2002 is wired @ 2 ohms on each channel and its pushing around 150w. i guess that is still rather low, but then what explains how the other night when i got off work the other night, the battery was dead, i drive around 30-35 miles to work @ speeds between 40-70 MPH(except when theres damn tourists on the road). that day i got there like 25 mins early so i was just sitting in my car listing to music ,@ a low volume, for about 15-20 mins, and the i went to work, lights off, door closed everything. when i come back it wont start(A real PITA when u have to wait for AAA at 11:00pm and then drive about 40mins to get home) any ideas?


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## sr20dem0n (Mar 19, 2003)

So that's a little more power, but still nothing to be concerned about really as long as you aren't clipping the amps or playing test tones. Most music peaks about 10dB above the average, so if you set your gains so that you don't clip on the peaks, that means that on average your amps will only be putting out about 1/10 of their rated power, so around 45-50 rms in your case at full, unclipped output with music. The key word there is unclipped, because if you start to clip them the power can increase dramatically, and it's a very good sign that your amps are too small for your listening habits.

What probably happened that one night is you were just sucking more current than the alt can provide at idle so it was coming from the battery, which ran it dead. This could have been caused by a few things. First is that the alt can only put out a small fraction of its rated current at idle, an 80 amp alt might be able to do 20-30 amps at idle. If you had your lights on, A/C on, etc that will easily take about that much current, leaving nothing for the amps (that is if your car was on at the time, if it was off then go to the next point). Also, running a car battery dead is very bad for it (unless it's a deep cycle). If you've done this before, you might have killed a few of the cells inside the battery, which will reduce its capacity dramatically, making it much easier for it to go dead again in the future.


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## jlee1469 (Dec 4, 2003)

I'm running a system putting about 700-800rms and I'm having no trouble with power issues. However I dont really listen to loud, so i'm assuming the amps are putting 1/2 that number.

I tend to listen to my stereo with my car off for long periods of time not too loud though. A few times I couldn't start my car so I had to recharge it. Sometimes the car struggles to start but does.

Did i significantly kill the life of my battery?


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## captain_shrapnel (Sep 10, 2004)

Yeah, a normal car battery is easily injured by a few deep discharges. You need a deep cycle battery for that kind of abuse... something like the Optima Yellow Top.


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## sr20dem0n (Mar 19, 2003)

jlee1469 said:


> Did i significantly kill the life of my battery?



It's really pot luck, sometimes it will damage the battery, sometimes it won't, it depends on how long it stays discharged. I've ran my stock battery dead once, and almost dead twice. The time it went completely dead, it was that way for about 2 days, it was pretty bad. The other 2 times I had left my lights on and came back after ~2 hours and it wouldn't start, but after waiting about 10 min it was able to "recharge" itself enough to start. I've probably lost some capacity, but it's still kicking strong, especially for a stock battery that's about 4.5 years old. It's not a good thing at all to run it that low, and you should prevent it at all costs. If you're listening to music with the car stopped for extended periods just start the car every 10 minutes or so and let it run through the next couple of songs before shutting it off again.


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## makaveli (Oct 5, 2005)

well thanks for the replies. couple more quickes
my HU has 2v preouts, causing me to have to set the amps gains fairly high to achive maxium power, this increases the current draw right? as opposed to a 4v output and the gains lower on the amps.
Also if my battery puts out ~12.8V with the car off and ~13.8 under a load with the car on, is it ok? or is there no way to tell if ie "hurt" my battery?
thanks


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## sr20dem0n (Mar 19, 2003)

No, the power drawn by the amp is a function of the power being sent to the speakers alone, it has nothing to do with the gain setting. If you're playing at 90dB, the amp will be drawing the exact same amount of power from the electrical system whether you have 5V preouts and the gain all the way down or .1V preouts and the gain all the way up.


12.5V-12.8V with the car off and 13.8V-14.4V with the car on is normal, the only way to tell if you've damaged the battery is to compare the capacity now to when it was new (draw a set amount of current, time how long it takes until the battery has reached ~10.5V)


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