Power amp breakup when revs drop and I have heavy current drain
Hi
I have a serious loss of current to my amp when my revs drop and I am using a lot of electrical items: lights, heater, etc.
I have a 4x60 watt amp with two of the channels bridged to drive a 12" sub and the other two driving a pair of Alpine mids.
I have the power terminal attached directly to the battery (as frabkly I can't find anything else to attach it to) but it obviously isn't on all the time; I have a turn-on wire attached to the ignition. I suppose the first place I should go is with some much heavier power cable like 4-gauge, although it wouldn't be terribly easy to run all the way to the back of the car, and I might still be faced with the issue that the battery still can't power everything with a midwinter load no matter how heavy the cable.
Here's a question: does the ground wire need to be as heavy as the power wire?
I really like having a decent stereo, but I am not that much into it to spend hours fussing on it, nor am I really interested in buying mammoth storage capacitors at a hundred bucks a pop.
I'm have been thinking it would make more sense to toss an extra battery in the back and run a short power cable to the amp and use the cable attached to the battery to keep this second battery charged. Way too elegant and simple to work, so maybe someone would tell me either why it won't work, or what I need to stop the second battery from overcharging (if you can overcharge a battery, that is).
First, yes you can overcharge a battery, it'll even get to the point of exploding if charged enough. You can try the 2 battery system if you want, it's been done before. You can also get better cables for it, the ground wire doesn't have to be the same size as the power cable but you could if you wanted.
About the charging, you can either get a high output alternator, or a 1 farad capacitor to stop the charging issue. You're just not putting out enough power to supply everything, you need to do one of those two things.
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I agree with eagle. I think all you need is a higher output alternator. you really shouldn't need an extra batt.
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Jeez you shoudln't have much trouble. i had two 15 inch subs (400max) (unbridged) and a little dual speaker box i built (2 cheap 120max 6.5's Sealed) hooked up to the amp and wasn't all the way up on the amp becouse its a 600 but i never had any trouble except the lights dimming slightly but you had to be parked and watching carefully to notice , this was also in the winter with the heat blasting rear defroster, wipers, and headlights on. it could be the altinator or a bad battery. i have a 4ga wire running about 18" to the fuse from the battery and 8ga. to the trunk. i used like 20 or 24 gauge for the ground and thats about 3'. but then again i don't know how powerful your system is, do you have any arching? is the bridge cleanly and properly connected?
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Hi
Yes, I would agree it could either be the alternator or battery. The battery is fairly new, although it's an AUtoZone battery and I've had nothing but trouble with their batteries, so who knows.
A bigger alternator would probably help. I haven't had this much trouble before with other cars.
Phil
OK... lets start with power wires. First of all, with a 60x4 amplifier, you should be fine with an 8 gauge power wire. You didn't specify what you have now. Make sure that you have a fuse on this wire within 18 inches of the battery. This fuse must match the fuse on the amplifier. This is for the protection of your car, not the amp.
Now, the ground wire should be as big or bigger than the power wire. In your case, 8 gauge will do fine. This ground wire should be mounted to a metal portion of the car with the paint removed. I like to use seat bolts for this. The wire should be as short as possible depending on where your amp is mounted. I suspect that the ground is your problem. Make sure all the connections are solid, ESPECIALLY the ground.
An amp the size of yours will NOT require a larger alternator at all. It wouldn't be a bad idea to have it checked at auto zone or something though. With what you have, and what you have described, start with that ground wire. Make sure its short, wire is large enough, and the connection to the amp AND car is solid.
By the way... how big is your power wire? That could be a factor also.
Hi
Thanks for your input. I'm not sure what my power wire is; maybe 14 and certainly no more than 12, but here's the thing: when the car is not running and there is no other electrical demand I can get the thing easily louder than I need it to go which is why I am surprised and perplexed that this is happening and I am willing to blame either the battery or the alternator because it only happens when the revs drop to idle.
I would have thought that 750 rpm would still be enough to create output from a modern alternator, and even if it didn't I would then expect a battery to be able to supply all the amps a car needs for the few seconds it is idling. I don't know anything about the laws of physics as they relate to amps and volts but it seems to me that there isn't any point shelling out for 8-gauge wire if the current just isn't there to go down it. I'd feel pretty silly with a booming stereo and have my lights go out.
If you could explain why this is happening and how wrestling with 8-gauge wire would solve the problem I'm sure I would go ahead and do it. Maybe I should steal my wifes two-week-old battery for a while first, see what happens with that. Autozone batteries are pure crap IMHO.
Thanks
Phil
Whenever you have current going through a wire to an amplifier, you are going to have current loss. The smaller the wire, the more loss you are going to have. The amplifier may be seeing 12-14 volts but its the current or flow of power that the amp needs to make power. If I had to guess... your have your amp in the trunk. If the wire is installed correctly then you should be using anywhere from 15-20ft of power wire to the amplifier. Using 14 gauge or even 12 gauge just won't cut it when it comes to suppling the proper amount of current that the amp needs to make power. 14-16 gauge is good for speaker wire, and 12 gauge is good for subwoofers, but not for power wire. That is why you are losing power at lower RPM's. Esp. with all the other accessories going at the same time. It seems that you don't have a lack of power, but a lack of current. The ground wire is also carrying current to complete the circuit, so it also needs to be of adequate size in order to have proper flow. Basically, the longer the wire, the larger it needs to be. If you had a problem with your battery or alternator, then you would have trouble starting your car, or at least you would be able to hear the starter turning slower.
Power amp breakup when revs drop and I have heavy current drain 
