If you have large accessories installed on your vehicle, such as a very powerful stereo system, you could put a lot of strain on the electrical system. If you feel that these accessories are not getting the energy they need or the headlights are much dimmer than normal, it may be time to install a capacitor. This is an additional element that functions as a current storage device and increases the vehicle's power supply capabilities. An auto electrician is perfectly capable of installing it, but you may find that the project is quite simple and that you can complete it yourself.
Steps
Part 1 of 3: Choosing a Capacitor
Step 1. Understand the basic concept of this element
The capacitor acts as a "reservoir" of electrical energy. The amount of current it can accumulate is measured in farads and as a general rule you should need one farad of capacity for every kilowatt of power you need in your plant.
Step 2. Decide if you want to install an internal meter or not
Some capacitors come with a meter that shows the amount of charge. If you opt for this solution, you must wire the meter to a circuit with a switch that turns it off when you turn off the vehicle; otherwise, the device always remains active and drains the battery.
Step 3. Purchase the capacitor
If you need this component, chances are you've already invested some in electrical accessories for the car. The price of a capacitor varies from 30 to 200 euros according to the size and characteristics; however, remember that all these devices perform the same function and that in most cases a 1 farad capacitor without an internal meter is more than enough.
Part 2 of 3: Install the Capacitor
Step 1. Make sure it has been downloaded
A charged capacitor releases a large amount of energy very quickly, which can be dangerous. You should always handle electrical components with great care.
Step 2. Disconnect the ground wire from the battery
In this way, you cut off the power supply of the car and you can work safely.
If a capacitor is already present in the system, it must be discharged; this element stores energy and you may get a very strong shock if you touch it even after disconnecting the battery
Step 3. Mount the capacitor
It can be inserted in many points of the circuit; the differences in performance are negligible, so the area in which you decide to place it is not very important. However, it is generally preferred to place it near the device that has difficulty in receiving electricity (for example, lights that tend to go out); whatever your decision, find a suitable location away from passengers.
Even if you are installing the capacitor to compensate for the extra electricity that the new accessories are absorbing (such as a powerful stereo system), remember that this element acts as a "reservoir" of current that powers the whole system. By installing it near those parts that are not receiving enough power, you can guarantee their power supply with minimal loss caused by the resistance of the long cable
Step 4. Connect the capacitor to the positive terminal
Whether you are connecting it to a battery, amplifier or distribution block of some kind, you must connect its positive terminal to the positive terminal of the other device through a cable; generally, 8 gauge wiring is recommended.
Step 5. Join the negative terminal
It must be connected to earth.
Step 6. Secure the remote turn-on cable
If the capacitor has an internal meter, it also has a third wire which is used to interrupt the power supply to the meter every time you turn off the car. You must connect this wiring to a 12 volt power source with a switch (such as the ignition switch or amplifier).
Step 7. Reconnect the ground wire to the negative battery terminal
By doing so, you restore the electrical circuit allowing all devices to function.
Part 3 of 3: Charge the Capacitor
Step 1. Locate the main fuse of the audio system
This element is installed on the circuit and prevents the electrical components of the car from being damaged; however, you must remove it before charging the capacitor. You should find this near the battery or the main wiring harness of the music system.
Step 2. Pull out the main fuse
In this way you can place the resistor that helps the capacitor to charge more slowly, thus preventing possible damage to the capacitor itself and to the whole system.
Step 3. Insert the resistor into the main fuse housing
A 1 watt and 500-1000 ohm resistor is generally recommended. A high impedance resistor (a higher number of ohms) causes the capacitor to charge more slowly, protecting the system from damage; join the positive terminal of the capacitor to the resistor.
Step 4. Measure the voltage across the capacitor using a voltmeter
Alternatively, use a multimeter; set it to measure the voltage of the direct current, contact the positive probe of the instrument with the positive terminal of the capacitor and ground the negative probe. When the voltmeter reports a value of 11-12 volts, the capacitor is charged.
Another method is to wire a phase finder to the positive pole of the capacitor and to the power supply circuit. As the capacitor charges, current flows through the phase finder and the light should remain on. Once the capacitor is charged, the phase finder switches off because the current does not flow (the voltage between the power supply cable and the capacitor should be zero)
Step 5. Remove the voltmeter
It is no longer necessary to monitor the status of the capacitor; if you used the phase finder instead, you can disconnect it.
Step 6. Remove the resistor
Disconnect the positive terminal of the capacitor from the resistor and disconnect the latter from the power cable; now you don't need it anymore, so you can put it away in case you need to recharge the capacitor in the future.
Step 7. Place the main fuse in its place
In this way, the system receives electricity again.
Advice
- If the electrical problem persists despite an increased energy input from the capacitor, it may be time to change the vehicle's alternator.
- Always prioritize safety when working with a charged capacitor; wear goggles or a protective mask and remove jewelry.
- Most models are equipped with a safety circuit that turns on to warn that the connections are not correct; if the light comes on, disassemble the condenser and check the work done again.
Warnings
- Never hold a capacitor in your hand while charging or discharging it; it can get very hot and, if it is too small, it could explode.
- Never install a discharged capacitor, as it instantly absorbs a lot of energy from the circuit and could blow all the fuses; always charge it before you mount it.
- Discharge the capacitor before disconnecting it from the circuit; you can do this by connecting the resistor across the capacitor.
