Is a 270 amp alternator enough?

[rockFord_Expedition]

I'm running 11k on a single 270a, with a good batt bank of course

Should be fine for you with a couple nice batts

11k rms? On a 270A alt?

With all due respect, I challenge that.

I have no question that your total rated output is 11k and your beat pounds.

The reason I say I challenge that is take the formula (one of them) to find watts of power. W=VxA

For your benefit lets say your alt puts out a full 270A even when it's hot, AND let's say that nothing else in your vehicle, including the vehicle it's self needs any of that power.

To get 11kw from 270A of current, you need roughly 40.7 volts.

No matter how good of a 12V reserve you've got, you aren't approaching 11k my friend.

OP, on a 270A alt in an ideal 14.4 V situation, 3888 is the absolute max wattage. And that's assuming 100% efficiency from the amps, no other current draw etc.

Hate to rain on anyone's parade, but I wanted to shed a little realism without upsetting anyone.

[Zak Massey]

I have a DC 270xp alternator. And Rockford I believe he means with the car on it would keep them running at 14.4v so if it drops under 13 that's a no go.

[tacomaguy1]

I'm running 11k on a single 270a, with a good batt bank of course

Should be fine for you with a couple nice batts

11k rms? On a 270A alt?

With all due respect, I challenge that.

I have no question that your total rated output is 11k and your beat pounds.

The reason I say I challenge that is take the formula (one of them) to find watts of power. W=VxA

For your benefit lets say your alt puts out a full 270A even when it's hot, AND let's say that nothing else in your vehicle, including the vehicle it's self needs any of that power.

To get 11kw from 270A of current, you need roughly 40.7 volts.

No matter how good of a 12V reserve you've got, you aren't approaching 11k my friend.

OP, on a 270A alt in an ideal 14.4 V situation, 3888 is the absolute max wattage. And that's assuming 100% efficiency from the amps, no other current draw etc.

Hate to rain on anyone's parade, but I wanted to shed a little realism without upsetting anyone.

I didn't say 11k clamped....2 5500s at .35 each so. 11k rated I guess lol

Singer 270

Did it with a DC 270xp too

[rockFord_Expedition]

I have a DC 270xp alternator. And Rockford I believe he means with the car on it would keep them running at 14.4v so if it drops under 13 that's a no go.

True. With the car running is what I assume we are talking about.

Remember this though. It isn't true to say "the more batteries the better"

If you are dropping below 12.4 -12.7 then yes, adding (good) batteries will help stabilize that. However for maintaining an operating voltage above 13 or 14 (unless we are talking about batteries rated above 12V) then your alternator is doing ALL of the work there, and additional batteries just means they are leaching current to maintain a surface charge of 13.xx

[Sergeant_Skyrim]

I have a DC 270xp alternator. And Rockford I believe he means with the car on it would keep them running at 14.4v so if it drops under 13 that's a no go.

True. With the car running is what I assume we are talking about.

Remember this though. It isn't true to say "the more batteries the better"

If you are dropping below 12.4 -12.7 then yes, adding (good) batteries will help stabilize that. However for maintaining an operating voltage above 13 or 14 (unless we are talking about batteries rated above 12V) then your alternator is doing ALL of the work there, and additional batteries just means they are leaching current to maintain a surface charge of 13.xx

The more battery reserve you have though gives you a longer play time. Nobody is saying that a single 270amp alt will keep any amount of batteries at the 14.8 volts it charges at. However, the more batteries you have the longer you will be able to play before you start dipping as low in voltage as you would with a lesser amount of battery reserve.

And as for your power equation there, you're saying that W=VxA. However, you are using the wrong amount of amperage. You need to use the amount of current (in amps) that your amplifier pulls. My DC 9k for example has a fuse rating of 900A for example. 900amp*14.4V=12,960. Of course it's not ever going to pull the full 900 amps, but I'm trying to use this as an example to reinforce that the amperage you use in that equation isn't the amperage of the alt, but rather how much current the amps are pulling from your battery reserve

[Zak Massey]

I guess its time to go grab a volt meter and see what my cars doing then! Last night on my drive home from work my lights were dimming a ton so I would say I've probably not got enough batteries. haha. My trunk is going to hate me. I just hope after adding the 1-2 batteries I still have room for my amps back there!

[rockFord_Expedition]

I have a DC 270xp alternator. And Rockford I believe he means with the car on it would keep them running at 14.4v so if it drops under 13 that's a no go.

True. With the car running is what I assume we are talking about.

Remember this though. It isn't true to say "the more batteries the better"

If you are dropping below 12.4 -12.7 then yes, adding (good) batteries will help stabilize that. However for maintaining an operating voltage above 13 or 14 (unless we are talking about batteries rated above 12V) then your alternator is doing ALL of the work there, and additional batteries just means they are leaching current to maintain a surface charge of 13.xx

The more battery reserve you have though gives you a longer play time. Nobody is saying that a single 270amp alt will keep any amount of batteries at the 14.8 volts it charges at. However, the more batteries you have the longer you will be able to play before you start dipping as low in voltage as you would with a lesser amount of battery reserve.

And as for your power equation there, you're saying that W=VxA. However, you are using the wrong amount of amperage. You need to use the amount of current (in amps) that your amplifier pulls. My DC 9k for example has a fuse rating of 900A for example. 900amp*14.4V=12,960. Of course it's not ever going to pull the full 900 amps, but I'm trying to use this as an example to reinforce that the amperage you use in that equation isn't the amperage of the alt, but rather how much current the amps are pulling from your battery reserve

Batteries are good for giving you more play time if you play without your car running. That isn't what we were talking about. They also give you more play time if you have really bad voltage drop, like below 12v. I'm not saying to never add more batteries, I'm just saying that there is a plateau, specific to each set up to where adding batteries becomes not so effective.

And in you analogy of the wattage formula, remember that amperage pulled from a battery can only be multiplied by the voltage available. If it is below your charging voltage then your alt isn't keeping up so your output number drops. So your example of 900A x 14.4V = 12,960 W is the power the amp receives, not what it puts out.

Good thread, good conversation. I like it.

[Zak Massey]

I have a DC 270xp alternator. And Rockford I believe he means with the car on it would keep them running at 14.4v so if it drops under 13 that's a no go.

True. With the car running is what I assume we are talking about.

Remember this though. It isn't true to say "the more batteries the better"

If you are dropping below 12.4 -12.7 then yes, adding (good) batteries will help stabilize that. However for maintaining an operating voltage above 13 or 14 (unless we are talking about batteries rated above 12V) then your alternator is doing ALL of the work there, and additional batteries just means they are leaching current to maintain a surface charge of 13.xx

The more battery reserve you have though gives you a longer play time. Nobody is saying that a single 270amp alt will keep any amount of batteries at the 14.8 volts it charges at. However, the more batteries you have the longer you will be able to play before you start dipping as low in voltage as you would with a lesser amount of battery reserve.

And as for your power equation there, you're saying that W=VxA. However, you are using the wrong amount of amperage. You need to use the amount of current (in amps) that your amplifier pulls. My DC 9k for example has a fuse rating of 900A for example. 900amp*14.4V=12,960. Of course it's not ever going to pull the full 900 amps, but I'm trying to use this as an example to reinforce that the amperage you use in that equation isn't the amperage of the alt, but rather how much current the amps are pulling from your battery reserve

Batteries are good for giving you more play time if you play without your car running. That isn't what we were talking about. They also give you more play time if you have really bad voltage drop, like below 12v. I'm not saying to never add more batteries, I'm just saying that there is a plateau, specific to each set up to where adding batteries becomes not so effective.

And in you analogy of the wattage formula, remember that amperage pulled from a battery can only be multiplied by the voltage available. If it is below your charging voltage then your alt isn't keeping up so your output number drops. So your example of 900A x 14.4V = 12,960 W is the power the amp receives, not what it puts out.

Good thread, good conversation. I like it.

Specifically quoting the last line. This is the most informative thread I've created yet. Normally I get very little help and no info out of it. This is amazing. You guys rock!

[rockFord_Expedition]

I guess its time to go grab a volt meter and see what my cars doing then! Last night on my drive home from work my lights were dimming a ton so I would say I've probably not got enough batteries. haha. My trunk is going to hate me. I just hope after adding the 1-2 batteries I still have room for my amps back there!

Yup. This is the way to do it. Dimming can occur dropping from 14.6 to 12.9 volts but that doesn't mean you would need to add more batteries.

Do you already have the DC 270 installed?

[Zak Massey]

Yes, it is in and has been for about 5 months. When I first put it in I only had one sub running with the second in the works.