Is an extra battery necessary???

[snakeye 10+ year member]

I'm planning on getting a 220 amp alternator in order to hook up my system. i have been told that I will need to run at least one more battery. i thought that the alternator ran everything once the car is on. whats the extra battery going to do?

I will be running my JBL GTO 75.4( about 100x4 @4) and my hifonics XXcolossus ( 3200x1 @2) Everything is 1/0 and big three will be done. I also have a 3+ farad cap that doubles as my distro block.

Also i need to double check what size fuse to use for the colossus, 250 or 300?

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[mjf 10+ year member]

get rid of the cap for one.

the second battery is a reserve.

 

[snakeye 10+ year member]

like i said i have the cap because it serves as a distribution block.

the second battery serves as reserve, so in case the alternators not putting out enough or to help the alternator not have to put out as much?

 

[SeanDub 10+ year member]

If you have 3kw+ rms, to say the least you need a second battery, or you probably will never see 3kw rms.