Car Audio- Capacitor Question

[Dylan Darbyshire]

Hey guys, I started wiring a new audio system for my friend today(new amp, 2 subs, and a capacitor)



The setup was bought used on ebay,



I have been reading how to install the capacitor and i need some help. It says that if you buy one new, you need to charge it first with a resistor before you hook it up to a battery. And ive read certain things about being carefull not to shock yourself because it can hold a very large charge.



So how exactly do i install this used capacitor without shocking myself? thanks

 

[Curt Brubaker]

Capacitors store a large amount of energy and they charge very quickly. First you'll want to verify that it is fully discharged before attempting to install it.



There are a few ways to accomplish verifying the discharge.



Take a test light, clip it to one terminal on the capacitor, and touch the probe to the other terminal of the capacitor. When the light goes out, you're done.



You can also hook it up to any device that runs off of 12V DC to the capacitor's terminals. (such as an old head unit etc.) When it stops working, you are done.



You must then "charge" your power capacitor using a resistor before connecting it directly to +12 volts. This is done with the a 1k ohm resistor and a voltmeter. The exact value of the resistor is not critical but I would keep it in the 500-1k ohm range. I would recommend getting a 1 watt resistor if possible. A lower wattage resistor will heat up too quickly. Also, do not hold the resistor with your bare hand. The current flowing through the resistor will cause the resistor to heat up and you could be burned. A good place to put the resistor is in the main power wire fuse holder. Simply substitute the resistor for the fuse. You will need to place a voltmeter across the capacitor to monitor the voltage. Once the voltmeter reads 12 volts you can remove the voltmeter and replace the resistor with the power fuse.



Alternatively you can measure the voltage across the charging resistor. It should start around 12 volts and slowly work its way down to 0 volts. When the voltage stops changing you have charged the capacitor completely.

 

[Jeff C]

As a resistor, I just use a 922 bulb (like one for the high mount brake light). Unbend the wires at the base, connect one side to the positive, the other to your power cable. While the cap is charging, the bulb will light up, when it's done charging, the light will go out. Same for discharge, except instead of attaching to the positive, attach to the ground. While power is transferring out of the cap, the bulb will light up, and once it is drained, the light will go out.