# Need help figuring out max power I can run

#### JuiceTin

##### CarAudio.com Recruit
This is all on stock electrical, amp output is (130amps), I can do a big 3 and maybe a second battery
With what I thought to decide your max power, is your amp out (130amps) times running voltage (14v) would be your max power I should use for an amp which is (1820w).
But I've heard people run over that that .
So how do I determine the max power I can run

First you should know that you also have to factor in the efficiency of the amp. If an amp is 80% efficient, that 1820 watts will only be 1456 watts from the amp (1820*.8).
Second, you can run more power than that if you have the battery capacity to supplement the extra power, but the issue there is that when the battery is depleted you will have to let the alternator charge it back up. That means turning down the volume until your voltage recovers.
I'm running a 5k amp with a stock alternator and 120 ah of lithium. I just have to keep an eye on my voltage and turn it down when the battery starts getting low.

if you have the battery capacity to supplement the extra power
Can you explain what to look for in a battery

N
First you should know that you also have to factor in the efficiency of the amp. If an amp is 80% efficient, that 1820 watts will only be 1456 watts from the amp (1820*.8).
Second, you can run more power than that if you have the battery capacity to supplement the extra power, but the issue there is that when the battery is depleted you will have to let the alternator charge it back up. That means turning down the volume until your voltage recovers.
I'm running a 5k amp with a stock alternator and 120 ah of lithium. I just have to keep an eye on my voltage and turn it down when the battery starts getting low.
I'm on the second battery, what could I run on just a standard car battery

N

I'm on the second battery, what could I run on just a standard car battery
That would depend on the capacity of the battery as well as the C rating. A standard flooded cell lead acid battery is usually not a great option for a second battery. You would want an AGM lead acid, preferably one marketed for car audio applications. Xs power is a popular brand. Do you have an idea about how much power you would want to run?
Alternatively, you could start with upgrading the alternator, and then in the future you can add more battery capacity if you want to upgrade.

That would depend on the capacity of the battery as well as the C rating. A standard flooded cell lead acid battery is usually not a great option for a second battery. You would want an AGM lead acid, preferably one marketed for car audio applications. Xs power is a popular brand. Do you have an idea about how much power you would want to run?
Alternatively, you could start with upgrading the alternator, and then in the future you can add more battery capacity if you want to upgrade.
I want maybe 3k 1500 per, or a little less

I want maybe 3k 1500 per, or a little less
Ok sounds like I need another battery, what should I be looking for

Ok sounds like I need another battery, what should I be looking for
The general rule of thumb that I've always been told is 100ah of AGM for every 1000 watts you want to run, but I went straight to lithium so I don't have personal experience with lead batteries. I believe there's a calculator on the ultimate car audio app that can tell you how much battery capacity you need, but I've also never used that.
I would personally recommend a small lithium bank, a 56 ah headway bank would be good for 3kw and definitely cheaper than buying 300 ah of AGMs, but I know some people prefer to stick with lead.

You don't need a second battery for that. A battery is a storage bank, and an alternator recharges. If you want to be able to play your music longer with the vehicle off, then you need more battery bank. If you want your battery to not be drained while you are driving then an alternator recharges it.

There's a lot more to it than a straight answer, it's relative to you.
Lets say you have 1500w going to your sub.
1500w / (yeah 80% amp efficient is easy, but you can usually find what yours is) .8 = 1875w draw
1875w draw / 14.4v (which is standard running voltage, some alts go higher), = 130 amp draw.

So when this is at full volume (set properly for 1500w), and hitting hard, it's drawing 130amps. Between those bass hits, its drawing less. If you're listening to bass heavy rap, or generated bass tracks, it could be drawing constantly. If you listen to rock or country, you've got a few seconds between bass hits, and are mostly charging. You could have a larger amperage draw if there is more recovery time, and you won't notice the draw.

Then you have to add that on top of what your vehicle uses. Your stock alt is sized so that if everything is on: AC, electric fans, efi, taillights, head lights, turns, horns, cig lighter, map lights, etc.. are all drawing, you have a little head room.

What you should really do is start with an alternator. When you want to put in a sub amp, you need to see what larger alt options you have. You need to see what is in your budget and what are your goals. Then you can work backwards if you want:
Lets say you can find a 300amp alt. If your stock is 130, and you use the AC, and don't want any trouble, you could take 300- lets say 100-120 out, and you would have 180-200 amps to work with.
200 x 14.4v = 2880 watts
2880w x amp efficiency = 2304 amp watt output

Then you have to figure out what you listen to, and about how often it's going to have subs hit. With rock and country, you could easily bump that up to 3,000 watts and not have an issue. With generated bass tracks, you are already right there. You just have to figure out your budget and goals, and most of the time meet somewhere in the middle.

If your stock is 130, and you use the AC, and don't want any trouble, you could take 300- lets say 100-120 out, and you would have 180-200 amps to work with.
200 x 14.4v = 2880 watts
2880w x amp efficiency = 2304 amp watt output
so your saying i should be looking into amp draw, (also i really only paly generated bass tracks(rebassed music)), and for now lets say no ac

as stock (130amps) 130 x 14.4 = 1872(watts)
1872 X 0.8 = 1497.6
that would mean i can run up to around 1400 watts on stock electrical
does that sound about right

so your saying i should be looking into amp draw, (also i really only paly generated bass tracks(rebassed music)), and for now lets say no ac

as stock (130amps) 130 x 14.4 = 1872(watts)
1872 X 0.8 = 1497.6
that would mean i can run up to around 1400 watts on stock electrical
does that sound about right
amp draw is going to come into play regardless, that's how watts are calculated. What Hardofwhoring is suggesting is that you focus on upgrading your alternator instead of adding a second battery. That is definitely a valid option. I was suggesting batteries due to your original question stating that you had stock electrical and could add a second battery.
A high output alternator would definitely give you the ability to run more power. I like to be conservative with my numbers just to be on the safe side. Your vehicle will always have its own current draw when it's running, even with all accessories turned off. So you can reasonably assume that a good chunk of your stock alternator power is going to running the vehicle. Lets say 50 amps for simplicity. So if you can get a 300 amp alternator that would leave you with 250 amps. 250ampsX14voltsX0.8efficiency gives you 2800 watts. Thats a fairly ideal situation, if your voltage drops due to a load from something like the AC or your main battery being charged, then that 2800 watts will drop too. Another thing with alternators is that they dont put out full power when youre idling due to RPMs being lower. At idle that 300 amp alternator might only put out 150, significantly lowering the available power. So if you want to play music while youre parked, such as giving demos or at a competition, you will need to have extra battery reserve along with the alternator. If you only turn your system up while the car is moving (and therefore your RPMs are higher) then battery reserve is less of an issue.

This is all on stock electrical, amp output is (130amps), I can do a big 3 and maybe a second battery
With what I thought to decide your max power, is your amp out (130amps) times running voltage (14v) would be your max power I should use for an amp which is (1820w).
But I've heard people run over that that .
So how do I determine the max power I can run
Playing rebassed music will draw more from your electrical than "normal" music but honestly with a second battery you should be able to run about 2000-2500w (a lot depends on how many amps your vehicle draws while running)

ok say i have a 300amp alternator
and want to use 6000 watts
how does a big battery play into this because
300 x 14.4 = 4320watts
if you had a really big system at some point you run out of alternator

* You need to see what your upgraded alternator options are, so you can get an idea of what your electrical options are.
* You also need to figure out what is your absolute finished goal with your stereo. Figure out what you would like to do if you money were no object.
* Now you need to smack yourself in the forehead and repeat after me, "I can't do that".
* Now like most of us, you need to figure out what is in your budget, plan your system out including electrical, and see what works for you.

An alternator is something you want to spend a little more the first time, and buy the biggest one you might need. A good one is a good chunk of cash. You don't want to buy another one down the road, because you're a little short.

Amps can be cheap. You can buy something to get you going and upgrade later if you need to. Especially if it's for your front/door speakers. You can buy a used 4x100 amp for \$50 used, \$100 new, and it will work, buy maybe have a little distortion that you probably won't notice, and YOU definitely probably wouldn't notice listening to generated bass tracks. If budget is a concern, this is something, (in your case for the fronts), I would get as cheap as I could, to get going.

Either buy the nicest speakers you want to have, or buy the cheapest ones that will get you buy until you can afford the good set. If front and rear have the same size, you can always put the fronts in the back when you upgrade. Again if it's just bass you're after, then buying \$500 components doesn't make sense. I would probably just get some really cheap two ways, to just fill the rest if the subs are the stars.

Sub amps can be dialed down no problem. If you know which subs you want, you can always buy something cheap/used to get you started, and dial the amp down until you get what you want.

Here's how I see a \$1,500 budget for this, I'm spending \$150-200 total on a cheap amp, with (4) two ways for the doors. I'm planning on \$400-\$500 for an alt. You need big 3, plus amp wiring, lets call it \$100-\$150 if you don't have tools. \$300-\$500 for a pretty decent mono amp. If I'm upgrading later, probably something like a smart 3 so I can play it at 1 or 2ohm, and probably some budget subs I find on marketplace or craigslist. With \$2K, I'm getting the good subs now, and adding in some sound deadener to the doors.

Some vehicles have multiple alt brackets, and you will need to start looking at multiple batteries with that. If you have a vehicle that has room, and won't rattle itself apart with a large build, like a tahoe, you can find the brackets.

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### JuiceTin

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