Please help - Capacitor wiring in battery powered amp - diyAudio
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Old 5th September 2013, 04:54 AM   #1
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Join Date: Sep 2013
Question Please help - Capacitor wiring in battery powered amp

Hi,
I need a little wiring advice, I have an infinity basslink (powered car subwoofer) that I am running off of a 12v battery for use in an outdoor stereo. I've noticed that it keeps cutting out so I am increasing the power wire gauge and going to add a 2 farad cap (cheap boss CPBL2). I'd like to know how to wire it...
So the cap has positive, negative and remote turn on.
the amp has positive, negative and remote turn on.

My guess is that I should go
Battery Positive -> Amp remote
Battery Positive -> Cap remote
Battery Positive -> Cap positive
Battery Negative -> Amp Negative
Battery Negative -> Cap negative
Cap Positive -> Amp Positive

Is this correct ? Also if I wanted to add an in-line fuse do I add it before or after the cap ?

Thank you.
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Old 6th September 2013, 04:18 AM   #2
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Fuse before the cap, towards the battery

Gajanan Phadte
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Old 6th September 2013, 06:11 AM   #3
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Thank you for the response, does the wiring sound correct?
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Old 6th September 2013, 08:48 PM   #4
dangus is offline dangus  Canada
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Location: Vancouver Island
You might need a bigger or healthier battery.
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Old 6th September 2013, 10:39 PM   #5
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Thank you for the reply. It may be that I need a new battery, but first I'll try adding the capacitor.
I have a feeling that my real problem was the thin power wire I was using, the capacitor is just added insurance. I won't really be able to test out anything until my next outdoor event.
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Old 6th September 2013, 11:17 PM   #6
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Location: California
Why in the world are you adding a capacitor? A car battery can supply 50A of current over short periods, at least a healthy one. The only thing that a large cap can help is when you have a run of small gauge wiring from your electrical system (in your car) to the amp that is wayyyyy in back of the car somewhere. The cap is a local charge reserve. If you are connected directly to the battery with good size wire (e.g. 10 gauge) and your connections are clean there is no real reason for adding a cap.
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Old 7th September 2013, 02:01 AM   #7
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I honestly believe you are correct. What I am essentially doing is throwing what I can at an issue and hoping it get's fixed. What I have made is a portable (relatively) DJ setup that I can transport via subway to places where I host free outdoor parties (usually monthly) in Tokyo on a small budget. It makes for some odd requirements and I'm always fighting size/weight issues. The whole thing is compounded by the fact that I can only really test if I have solved a problem at the party... Effectively all I can do at home is power on tests.
I am also not using a car battery, but am using a motorcycle battery. I did see a DIY cooler stereo using a motorcycle battery with the same capacitor I bought and figured I'd give it a try.
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Old 8th September 2013, 08:53 AM   #8
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Well I've got the cap, cut my wires and added the connectors. If there is something incorrect with the way I'm planning on wiring the capacitor please let me know. I'll be charging the cap soon for a power on test run
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Old 8th September 2013, 09:02 PM   #9
dangus is offline dangus  Canada
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Location: Vancouver Island
For that kind of application, I'd look at using a more efficient speaker. A sub in a box that small will not be very efficient, since in a car space is a bigger concern than power consumption. 10 watts into 99 dB speakers is as loud as 100 watts into 89 dB speakers, except there's less power compression, and 1/10 as much power drawn from the battery.

With relatively low power levels like that, a line source made up of inexpensive speakers may be feasible.

Last edited by dangus; 8th September 2013 at 09:06 PM.
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Old 8th September 2013, 10:32 PM   #10
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Join Date: Sep 2013
SPL was definitely one of my top considerations when buying the enclosure I got. I can't find the specs now, but I believe it was 93 db. Additionally I have no place in Tokyo to build an enclosure. Car speaker components are ridiculously expensive here so I am limited to Amazon US global shipping (very cheap shipping on some items). In the end the durable small design, cost, passive radiator and integrated amp won over on the less than desirable SPL. Next time I am in the US I will look into replacing the 10 in the box with a better more efficient sub, but 93 isn't terrible (of course now I can't find the SPL anywhere so I may be remembering it incorrectly).

It doesn't seem likely that I will get an answer to my electrical questions so I'm just going to power it all up after work tonight. Will charge the cap before plugging in the sub, and discharge it after.
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