When I flip the ignition switch from the "run" position to off, there is a momentary interuption of the power to the accessory circuit. Then, the power to the accessory circuit is back on until I open a door. This is frustrating when I want to continue to use the AVIC for Bluetooth or even just the A/V without idling the engine. Additionally, it can't be all that good to power down the AVIC, then immediately begin the boot-up process and then power it down again when I open the door a few seconds later.

So I figure adding a capacitor to the accessory circuit could give me a few milliseconds of power, long enough to keep it running during the brief power interuption. Unfortunatley I don't have the knowledge set to determine what size/type of cap would be approriate. Also, would I need a diode to keep from back-feeding the entire vehicle's accessory circuit?

This is not really just a Z-series specific question, but that's what I have. I tried searching here and elswhere but the question is not easy to querry.

Greg

Definately specific to your car.

Cap. is a great idea!

Unfortunately, I have little experience in this area.

Maybe Crutchfield can help:

How do I know what size capacitor to use in my system?[/url]":12q6t1ld] How do I know what size capacitor to use in my system?

 

The rule of thumb on capactior size used by most manufacturers is 1 Farad per 1,000 watts (RMS). Using this as your guide, then you would use

 

* a .5 Farad capacitor for systems up to 500 watts

* a 1 Farad capacitor for systems up to 1,000 watts

* a 2 Farad capacitor for systems up to 2,000 watts

 

When you calculate the power in your system you want to figure in actual used power, keeping in mind what you actually want running off of the capacitor.

 

For example, if you had a system that includes a head unit rated for 50 watts total output, an amp to run your highs rated for 350 watts, and an amp on your subs rated for 500 watts, then you would start out by looking at what you want to add capacitance to. The head unit in this example system would not be running any speakers off of it, so it would not be figured in. When considering the amplifiers, remember that the lower the frequency, the more power you need to reproduce it at the same volume as a higher frequency. Because of this (along with knowing what kind of power delivery you already have set up for the system) you may find that you only need to add the capacitor to the subwoofer amp, which at 500 watts would require a .5 Farad capacitor. If you wanted to include the highs amp as well, then you would want to use a 1 Farad capacitor.

 

Another thing to note on this topic is that you can't really add too much capacitance to your system, so it's safe to overshoot the guidelines. If you wanted to add three 1 Farad capacitors to a 1,000 watt system, it would not be a problem at all.

 

Article #482 - Last updated 10/10/2004