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1 farad power cap question

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rich_gale View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rich_gale Quote  Post ReplyReply Direct Link To This Post Topic: 1 farad power cap question
    Posted: 09 August 2008 at 5:54pm
Im in need of a little assistance with power cap selection.
 
i am currently using a small 12volt sealed lead acid battery to run a tiny little sony amplifier (xm-255nx) on a portable sound system (not in a car) and would like to know if adding a 1 farad capacitor will help the battery by taking care of the high current draws and keeping the current draw of the battery more uniform.  its not that the battery runs out of steam on a kickdrum, but i would like to know if the capacity will flatten out the current that gets pulled from the battery itself..
 
cheers
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Marvin View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Marvin Quote  Post ReplyReply Direct Link To This Post Posted: 03 September 2008 at 3:57pm

you will need to charge the cap up say in a car first. i the cap isnt charged then it will also add and drain battery to sustain its charge. the cap works by going inline before the amplifier and it gets it charge from the alternator. when a kickdrum note comes it will pull from a charged capacitor possibly drain it before getting any draw from the battery. if u were to play a mobile system with a capacitior i dont think it will help to be honest. because as i said once drained it will look to the battery to fill it back up.

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Jake_Fielder View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jake_Fielder Quote  Post ReplyReply Direct Link To This Post Posted: 03 September 2008 at 6:59pm
What he means is; will it be better for the 12v battery if the current draw is smoothed out (with a cap).
 
It will flatten out the current draw (to the battery) but i also doubt it would make any differance tbh.
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_djk_ View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _djk_ Quote  Post ReplyReply Direct Link To This Post Posted: 04 September 2008 at 11:24am
The average current draw from the battery will be the same with a big cap, but it will be able to provide higher peak current.
 
A battery is a chemical process, and s-l-o-w.
 
A 100,000µF cap would probably be OK for your small amp. I would also use a 470µF and maybe a 4.7µF mylar cap as well (big caps are slow too).
 
 
0.47F at 5.5V for $1.00, use three in series for 150,000µF at 16.5V, a 1000µF/35V electrolytic for $0.15, and a 10µF mylar for $1.
djk
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