# Audio Capacitor question?



## lotus197 (Apr 27, 2003)

I have a dvd player in the car. Now I want to run a surround sound for the movie but I need to know what size of "farad capacitor" I will need. I need to run the movie with the car off with full sound capabilities and still be able to start up my car after 2 hours? My sound system only pushes 400 watts but I will using only about 100 watts for the movies. My car is used every day so the battery is always getting charged by the alternator. wha do I need?


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## SuperblkStalion (Aug 26, 2002)

you need a deep cycle battery and a battery isolator kit installed if you plan to run a 2 hour movie wtih the car off. that is what deep cycle marine batterys are for. trust me on this. the kits are not that hard to install. well, you could always push start your car when the battery dies if your into that sort of stuff.


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## toolapcfan (Jul 10, 2002)

A capacitor won't really do anything for you while the car is off. All capacitors do is make sure that your voltage stays consistent. Since your alternator isn't charging when the car is off, your voltage will always be constant since the battery will be supplying it. Do what superblkstalion said, get a deep cycle battery to put in the trunk and an isolator kit and run all your ICE off of that. That way you won't drain your starting battery.


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## koshimaro (Jun 28, 2002)

maybe a yellow top or two? but as a general rule i read somewhere that it is half a farad cap per 500 watts..


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## holy200sx (Jan 8, 2003)

1 farad = 1000w..

do the math..


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## sr20dem0n (Mar 19, 2003)

A capacitor will do nothing for what you want. It seems today that all these car audio stores just throw caps at you claiming they will fix everything. Caps have a very small use and 98% of the people that have them don't need them.

Do what SuperblkStalion and toolapcfan said and get a deep cycle battery in the trunk

BTW - I'm pushing close to 1200rms and I don't have a cap and I have 0 problems. No light dimming, nothing


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## lotus197 (Apr 27, 2003)

ok, im guessing a blue optima? would work. now....... should I connect my amp and speakers to it as well? Does it need to be connected to something in order for it to get charged?


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## sr20dem0n (Mar 19, 2003)

Blue is for marine use (boats)

Yellow is the deep cycle, that's what you need. I would suggest putting the yellow top in the trunk, running a 0/1 ga wire connecting the + posts on each of your batteries, then ground the yellow top to the chassis. At the yellowtop in the trunk connect the 0/1 to a terminal like this. A quick turn of the knob and your two batteries are disconnected from each other. Hook all of your audio components, basically everything you want to be available to you to the other + post on the yellow top (this includes the headunit and all amps).

If you do all this, you can leave that battery isolator open normally and your yellow top will be charged from the alternator and everything will be working as one. When you go to watch a movie you turn the knob and it will disconnect the yellow top from the rest of the electrical system. This way you can watch your movie for however long the battery will last, if it runs out no big deal, you can still start your car normally from the main battery under the hood. Then when it's running you open that isolator and the alternator starts charging your yellowtop back up. Just make sure all of your audio/video equipment is hooked up to the yellowtop so none of it drains your real battery while playing a movie with the car off.

For the headunit you will have to run your permanent +12V wire back to the trunk, the switched power wire you can do with what you like. Either leave it connected as it is, then you will have to have the key in the ACC position in order to play the movie, or run it back with the permanent +12. Keep in mind, if you run it back with the permanent +12 your headunit will not turn off when you turn off the car. Personally I would leave the switched power hooked up as it is normally and just run the permanent +12 back to the yellowtop.

Sorry for the long post, but I believe you will understand what I mean and it should work out nicely. How long the yellowtop will last really depends on how much you have the audio cranked. Honestly I have no idea if it will make it through a whole movie or not but my guess is as long as you aren't blaring the sound it should. Good luck.


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## droppinbottom (Jun 30, 2003)

power cap should only be used on sub amps when drawing large amount of current. yellow top optima + battery isolator


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## Ninety-Nine SE-L (May 5, 2002)

got a quick Q about the 2 batteries thing. When you have the car on and both batteries on the same electrical system, how much extra strain will this put on the alternator during charging and normal use?


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## sr20dem0n (Mar 19, 2003)

Well if your battery is empty it will obviously put a pretty big strain on the alternator to charge it back up. But if your batteries are full it won't put any more strain on the alternator than before.


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