Sorry for asking such a basic question but I used the search feature and I can't find anything on it.

I am planning a build for a BL 15 in about 4 cubes and I need to know how many RMS I can safely put out on a sundown amp with a 130amp alternator without dipping below 12v too severely.

Depends on your reserve really. I've used around 2500 rated on 130 amps and two batts with no issues, but I don't bump around a lot.

Well all that I have right now is a duralast gold under the hood so would that suffice for 1k rms or maybe 1.5?

Shouldn't be a problem, but there also isn't really an audible difference between those so the smaller ought to be effective enough.

The Duralast batts are pretty good too. They held up to my current hogs in the 90s, so today's slightly more efficient amps shouldn't pose a problem at that power level.

I have a stock 130 amp in my suv with one of the big bish batts from walmart under the hood. My amp is a aq1200 and I could drop into the high 11's at times, usually during idle. I then added a d3100 and voltage is much better.

Wow dip into 11's with a AQ12? Hopefully a saz-1000 will be plenty and they are fairly efficient from what I've seen.

On my stock alt (don't know specs) and 2 batteries (stock one of 4 years old) and a Kinetic hc 1200 in the back I don't drop below 13.3with AC on. It stays at 13.6 without AC. Without any sound I may see 13.8 v while driving on the highway, not more.

I run a saz 1500 at 1 Ohm and a sax 50.4 bridged at 4 Ohms.

It was quite the same with only the stock battery. But voltage stays a lot more higher with engine off, with the 2nd battery.

If you have the money, get the 1500 for that sub, but the saz 1000 is enough and you won't hear the 500 w more !

Along a similar line to the OP's question, I've been told in order to use my Cadence ZRS-7500d that I would need at least a 200 amp alternator to safely power my system and the rest of my cars lights and whatnot. Here was the explanation. The Cadence has a 150 amp fuse, so with this math:

150 fuseamps / 1800 watts@1ohm = .083, or 8.3 amps per 100 watts, so 149.4 amps necessary. My current car's alternator is only 150 amps, so, to my knowledge, I need a bigger alternator. Is this correct?

My apologies for the thread-jack.

Edited July 20, 201213 yr by wannabang

Yes. you need some current help, but going by fusing is not entirely true. Music is dynamic and current will vary the entire time the system is being used.

For what it's worth I have run ~ 2000 rms with a 125 amp alternator. I had the biggest autozone battery that I could fit under the hood, and a duralast agm battery in the rear. I was fine but rarely went full tilt at idle.

and it's my understanding that an extra battery won't solve the issue of not enough current. right? /threadjack Sorry, OP

Depends on your reserve really. I've used around 2500 rated on 130 amps and two batts with no issues, but I don't bump around a lot.

You used an amp rated at 2500wrms with a 130a alternator and never dipped into the 12's?

and it's my understanding that an extra battery won't solve the issue of not enough current. right? /threadjack Sorry, OP

Not if you are running balls to the wall all the time and not letting the batteries charge.

and it's my understanding that an extra battery won't solve the issue of not enough current. right? /threadjack Sorry, OP

An extra battery (or a million extra batteries) will not prevent voltage drop from 14.xx to 12.xx volts.

I've got a 130 amp alt in my car and before I put an XS Power battery in the back I'd drop below 13.0 volts but with the battery the lowest its dropped has been 13.3. I'm running an MB.Quart Onx1500.1d with an SSA Icon.

I also don't have as much power as you will be, but my next build I plan on having 2500 watt amp in the back.

and it's my understanding that an extra battery won't solve the issue of not enough current. right? /threadjack Sorry, OP

An extra battery (or a million extra batteries) will not prevent voltage drop from 14.xx to 12.xx volts.

You'd be wrong there without qualifying that statement with a number of batteries, total battery capacity (Ah, not CCA) and total current draw. With enough batteries, or a small enough draw, the voltage won't dip hardly at all. You can completely compensate for amp draw with enough battery reserve (provided you give the alternator time to catch up and keep them topped off) and you can also overwhelm most any practical amount of reserve with huge amounts of current draw.

The reality is that average current draw is what you really care about. That determines the duty cycle of the alternator. When you average out all the peaks in current draw with all the valleys (assuming normal music, not something with continuous droning bass notes) most people would be surprised by how little their system draws. That number is really all the alternator needs to handle. The rapid transients are covered by the battery reserve. A good reserve will keep the voltage from dropping appreciably (more than adequate wiring matters here as well), but the biggest alternator (discovered to many's consternation) won't keep the voltage from dropping on high draw, rapid transients.