You can charge your car stereo capacitor by either using a test light or a resistor. After removing the fuse, connect either the test light or the resistor to the in-line fuse holder. For test lights, the capacitor is charged fully when the light bulb turns off. For resistors, it is a successful charge when the voltmeter reads out 11V to 12V.
Car stereo capacitors are fully discharged when you buy them due to safety installations. That’s why in most cases, you need to charge your capacitor before you can use it in your system.
There are two ways to charge a cap: via using a test light or via a resistor. Either way, these charging tools are often included in your purchase.
If you’re unsure if you really need a capacitor in your car, you can see our guide to capacitors.
Two Charging Methods For Your Car Stereo Capacitor
Before you can charge your capacitor, you need to remove the fuse first. This is an important step since the in-line fuse holder is where the resistor or the test light will need to plug to charge the capacity.
Set it aside to somewhere safe because the charging might take a couple of minutes.
Charging Capacitor Via Test Light
A test light is usually included in your capacitor’s package. If you don’t have a test light, you can buy it separately from reputable car accessories suppliers. Take note: don’t buy the small LED model; buy a 12-volt test light with a small bulb attached.
Connect the two terminals of the test light to the in-line fuse holder. Once this step is done, repower your car battery’s ground cable. The bulb should light up, and your capacitor will start charging. You can use alligator clips to make the process easier.
As the capacitor continues to charge, the light in the bulb will start fading away. It will continue for at least 10 to 30 minutes, depending on the capacitor. When successfully charged, the light will fade out completely. This means that the voltage went down to 0V (from 12V), which completely charged the capacitor.
At this point, you can remove the test light (be careful). Get the capacitor fuse that was removed earlier and connect it to the in-line fuse holder. You can now use your capacitor to its full features.
Charging Capacitor Via Resistor
Using a capacitor can be a little bit tricker. Just like the test light, the resistor should be included in your capacitor package. But if not, get a low resistance resistor with a high voltage.
It should be between 10 to 1,000 ohms and a rating of about 1-20 watts. If you’re not sure, you can always check the user manual.
Connect the resistor to the in-line fuse holder before powering up the ground cable for the car battery. At this step, the resistor should start to get hot. Wait for the capacitor to get fully charged (about 10 to 30 minutes.) You will know if a capacitor is charged up if the resistor is cool.
Use a voltmeter for a safer method, or check the visual monitor from the capacitor itself. If the voltmeter reads from 11 to 12V, your capacitor is now fully charged.
Remove the voltmeter and the resistor after charging. Reconnect the main power fuse to the in-line fuse holder.