Power Inverter 600w Setup Advice

**mcoutlawz** · 10-30-2008, 06:46 AM

Hello all. I'd be grateful for some advice regarding powering a carputer.

The setup I'm going for will be as simple, and portable as possible with no or hardly any modifications to the car needed. So I'm going for an in-dash flip down monitor (not a dvd player, just a monitor that has RCA video input). When I receive the screen I'll figure out how to power it.

But my main question at the moment is about powering the computer. I build computers all the time, and have an extensive amount of parts that are outdated, like old 800mhz baby atx AMD mobos etc. So building the coomputer to any specification is not a problem.

I don't want to go for a DC - DC PSU. I want to use an inverter, as I already have a 600w one (this one here - http://www.maplin.co.uk/Module.aspx?ModuleNo=48724). So, my plan is to connect the inverter directly to the battery, and connect the computer to the inverter. I don't mind switching the computer on and off when entering/exiting the vehicle.

I'll try and keep the computer's power consumption to a minimum as standard, under 200w.

Does anyone think I'll have a problem with this setup or can offer any advice/tips?

Thanks

**numbers** · 11-01-2008, 06:08 PM

Originally Posted by mcoutlawz

Does anyone think I'll have a problem with this setup or can offer any advice/tips?

Unless things have changed over the years, you're likely to get more advice than you bargained for. There are plenty of folks from whom the only "tip" you'll get is "buy a dc-dc power supply."

I'm not one of those people though, so here are my tips:

Measure the current draw of the inverter when switched off. Some inverters draw several hundred mA when off, and that can mean a discharged battery in the morning and a deceased battery after a few dozen such events. You may find that you need to add a separate power switch to completely turn it off.

Keep the ac power cable short and straight, and be mindful of where it is. It is more than happy to induce a 60hz buzz into your audio if you let it. Prepare yourself to use a ground loop isolator if it becomes necessary, even if you consider it a bandaid as may do. That inverter creates a rather large EM field and if you have a ground loop between any of your equipment which would otherwise be irrelevant, adding an inverter to feed it may require you to do something about it.

If you were hoping to use S3 stanby, stop hoping. The inefficiency of the inverter plus the atx power supply will amount to many times more than the power drawn by the computer itself and will drain even a yellowtop in just a few hours. Unless you rig a linear 5v regulator for standby power, hibernation and cold booting are your only options. Also, if you are considering a separate 5v standby supply, be wary of older motherboards. Power saving methods were horrid - if even present at all - on older hardware.

Lastly, it IS entirely possible to have a noise-free carpc setup using an inverter. No matter what anybody tells you, it's possible.

EDIT: And I don't mean to give advice that you didn't ask for, but I just want to make sure you're aware of the difference between vga resolution and rca resolution. If your monitor doesn't have vga input, your eyes will be in a world of hurt if you try to view normal text outside of a frontend.

**mcoutlawz** · 11-18-2008, 11:00 AM

Thanks a lot for your advice, and don't worry about giving me too much!

I've changed my mind about the RCA monitor, and gone for a VGA one instead. £250!

Anyway, that should be arriving tomorrow, so firstly I'm going to install that, then wire up the inverter, an old computer with a UPS power supply and give it a little test with the car running etc.

How do I measure the current draw of the inverter when switched off? With a multi-meter?

Thanks