When choosing batteries

[Carnines]

9k total, bass and mids highs, 6800 or 7k is going to the subs

Watts are watts.

[Larry BigCountry]

When choosing how many batteries to get, do you match your wattage needs exactly, or just go over by say 10% or double?

[Ninja_v1.0]

sorry I was looking for a serious answer, I know I don't need 8 batteries for 7k watts rms

Actually with the amount of alt power you have. You Do.. I would say at-least 4 d3100s

[mrd6]

Take my build as an example when I ran a ddzse, 7k rms. I ran a single mechman 240 alt and 6 xp3000s.

This allowed me to play close to full songs full tilt before giving it a break. With that setup I could demo for 1-2 minutes balls to the wall and stay above 12 volts. In the amount of time it took to switch songs, voltage was back and ready to go again.

240 amps of alt is really only good for a 3.5k amp max unless ypu start adding lots of batteries and or caps.

[Larry BigCountry]

so basically i'm limited because of the vehicle I drive since no one makes a dual alternator bracket?

[Massivespl]

Yea u need more alt or 6-7 d31 batts to run 7-9k one one little alt

[Larry BigCountry]

does anyone here design dual alt brackets? I have a dodge dakota

[mcfalcon]

Dc power might have something. Also mechman or singer might sell them but I'm not sure.

[mrd6]

so basically i'm limited because of the vehicle I drive since no one makes a dual alternator bracket?

Pretty much. I'm in the exact same boat. Now I'm trying to run 15k rms, still on the same 240a mechman with 8 banks of supercaps. It works...okay...but I'm not happy with it. I'll be finding someone to help.me fab up dual alts this winter.

[magillaru]

Like ninja said, you should be alright with 4 3100s.....start there and if you need to add one, do that. Regarding the alt, that will depend on how you're running your system.....playing full tilt while driving or at idle. If your car idles low, you might see some drop....if that happens, give it a little gas.