Need help powering in-car computers, PC accessories and monitors

[GiveMeTheJuice!]

First post. It is a pleasure to be here. I'm a software developer with gearhead/car guy roots and I'm blending three passions. The third is music. It sounds better loud   I'm posting to get some help connecting an inverter to my car.

My '13 Volt charges the 12V glass matt starter battery from the 10.4KWH traction battery. This allows people to run off the 12v for a very long time with the ignition on. Longer with a full tank of gas.

My TrippLite 1800W modified sine wave inverter works reliably. It has been flawless for 35k miles. But now I need to reduce the buzz noise when connecting either of the PC's (qty 3) to the factory head unit via stereo jack. The PC power supplies also emit a buzz that needs to go.

I have a Smart APC UPS SMT1000 ( pure sine wave ) that may handle my needs (650w). I connected the UPS battery leads to the Volts' starter battery and the unit wouldn't power on. The factory APC UPS battery is dead, so I tossed it.

I searched here for a bit (using my Droid Razr) but didnt see a post that explained what might be happening. Should this configuration (UPS to 12v) be functional?

[Falcon69]

Buzz noise?

Do You mean alternator or engine noise?

If so, I'm not sure if this may help, but...

When I was installing competition car stereo systems, I often upgraded the batter to frame ground cable, and then wherever the amplifiers were ground, i ran a 0 gauge cable from there, along the frame,  to where the battery was ground to the frame. This completely eliminated the noise issue.

[peter.mitchell]

UPSs as inverters often assume the battery connection is floating/isolated compared to the UPS output, because they are often sealed units and are very well insulated. If the battery terminals aren't isolated from the output (eg, the UPS is grounding through the car chassis), this may cause issues.

[GiveMeTheJuice!]

Buzz noise?

Do You mean alternator or engine noise?

If so, I'm not sure if this may help, but...

When I was installing competition car stereo systems, I often upgraded the batter to frame ground cable, and then wherever the amplifiers were ground, i ran a 0 gauge cable from there, along the frame,  to where the battery was ground to the frame. This completely eliminated the noise issue.

Buzz noise is inherit of modified sine wave inverters like the one I have running.

The Chevy Volt uses a transducer instead of an alternator. The engine can be off (but ignition on) and you can hook up a few amps pushing 18" woofers. I think about competition stereo systems all the time for this very reason as well as wanting to know what software would be useful to those mid to high budget stereo system installers and/or owners.

What was it like for you in the competition stereo scene?

[GiveMeTheJuice!]

UPSs as inverters often assume the battery connection is floating/isolated compared to the UPS output, because they are often sealed units and are very well insulated. If the battery terminals aren't isolated from the output (eg, the UPS is grounding through the car chassis), this may cause issues.

Because I added chassis ground to the UPS (12V starter battery I assume is frame grounded) circuit, this may be causing problems. Is that what you mean?

Would grounding the UPS chassis to the car frame be a possible solution, or something to try?

[Falcon69]

What was it like for you in the competition stereo scene?

Loud!  Expensive, and fun. This was back in the late 90's.  Things are alittle different now.

[GiveMeTheJuice!]

ping...