Capacitor Question

[mrmackie305]

I was doing some rewiring in my audio system the other day and had my head unit and amps on for a while without the car on. I suddenly noticed that when I would go to turn up the music, the amps would cut out and then try to turn back on. I thought they might not be getting enough power so I went to turn my car on and it wouldn't start! (my battery died) I decided to just get a new battery because the battery was 5 years old. I replaced the battery, but the sub amp still kicks off when I try to turn up the music. So here's my question....I have a capacitor for the amp, do you need to recharge capacitors when you replace a battery? My thinking is that the capacitor might be trying to charge while at the same time the amp is trying to draw power so it wouldn't get enough. Any help would be appreciated!

-Ben

 

[jvtran]

yes from my experience you will have to discharge the cap completely then recharge the cap accordingly with the correct resistor.

however looking at the main issue, it sound like not a problem with the cap or batteyr but maybe a load impedance issue. what speaker ohm load at you placing on the amp? make sure it is not lower than the minimum impedance load that the amp can handle. I've had issues before like yours where the music would cut out when volume is turned up and it was because the amp impedance was being loaded too low.

 

[mrmackie305]

I think it is probably a problem with my capacitor because I've had the system hooked up for over a year and it has worked fine. I will try to discharge and recharge the capacitor tonight and let you know the results.

Thanks for the quick responce!

 

[mrmackie305]

Well I finally had time to recharge the capacitor...and I'm still having problems! The amp turns on but as I start to turn up the bass level, the light on the amp begins to dim and then it turns off. Does anyone have any suggestions of what the problem may be?

I'm running a kicker amp kx350.2 (4-ohm 350 watt RMS) to an Infinity Kappa Perfect 12.1 12" subwoofer (4-ohm 75-350 watts RMS). I'm running this with a royal red capacitor (1.2 farad).

 

[tarheeltp17]

ditch the cap and see what happens.

 

[Light_Mania]

It definitely sounds like your amp is not getting the power it needs. If this is a new development, I would recheck the power wiring back to the battery. Sounds like there is a voltage drop somewhere along the way, perhaps due to corrosion at a connector or broken multistrand wire where it might be subjected to movement.

The power capacitor is only to help with extremely short transients. This sounds like a problem with the supply of sustained power, not a capacitor issue.

 

[tarheeltp17]

It could very easily be a capacitor issue... if the capacitor is continuously trying to recharge itself then the amps won't get the voltage they need. The cap could also have internal problems which keep sufficient amount of voltage to reach the amp. I've seen several cars where caps were wired into their system and at the cap they had 12+ volts when the car was running at the cap, but at the amp they had around 7-8 volts which is obviously not enough. Disconnected the cap and the amp measured 12+ volts like it should.

Caps are way overratted anyway... you really need to upgrade your big 3, switch battery to an optima yellow or red top, then possibly a cap. Generally speaking you need a 1 farad cap for every 500 watts. Believe it or not but caps can actually cause more long term damage than you think if you don't do other upgrades first.

 

[mrmackie305]

I figured out what the problem was yesterday. After bypassing the capacitor the amp still had a problem, so I decided to disconnect the output wires to see what that did. When I did this, the amp stayed on. So I looked closely at the cable going to the sub and discovered that it had gotten crushed. I have it coming out through the middle of the two back seats, and somehow it had slipped into the hinge and got smashed. I replaced the cable and it worked fine!

So the lesson I learned....sometimes the problem is A LOT less complicated than you make it!

I appreciate everyone's help on this issue!

-Ben

 

[Light_Mania]

So the wire to the subwoofer was shorted and the amplifier was trying to drive an extremely low resistance circuit? I'm surprised the output wasn't fused, and impressed the amplifier could take it without damage! Glad you got it sorted out.

 

[jvtran]

hey, so my load impedance idea/recommendation was kinda close... hehe

 

[tarheeltp17]

most decent amps on the market will go into protect mode if they detect something wrong... which is exactly what his was doing.