I'm looking from some input on how I could go about hooking up the pc with doing as little as damage as possible to the battery?

 

What are your power requirements?

 

The m4 dc-dc psu is rated at 250W and peak of 300W. The processor runs at 73W or at least under full load so. Then I will have a usb mouse and keyboard connected and usb wi-fi other than that nothing else will be connected.

 

What do you mean by doing damage to the battery?

I have a Carnetix P1900 carPC power supply connected to my battery and it has been working wonderfully.

 

I'm just worried about pulling the battery down and then the car not starting.

 

I'm not sure how the M4 works but my P1900 starts up when the ignition is on and shuts off 15 minutes after the ignition has been in the off position. The P1900 will also shut everything off if it detects the voltage of the battery drops below a certain level. I'm pretty sure the M4 should have similar features. So far I have never gone to my car with a dead battery and I've been running a carPC for about 3 years now.

 

You'll want to hook it up for your PSU's maximum amperage draw, which at 300W would be 25amps. (DC-DC PSU's are very efficient) So.. get a 25amp fuse and put it in line with your +12v main power cable that is powering the computer. With your setup it will never see that type of power draw, you'll probably be around 40W - 70W average. Also make sure you have a good ground. Setup the power supply jumper to turn on the computer when a switched +12v signal is detected, and to a <30sec delayed shut down when the switched +12v goes off. The PSU should have a jumper to plug into your computer's power switch leads on the motherboard. It will give the computer the power on and shut down signal. In Windows 7 or whatever you're using, have the computer set to 'shut down' on power button press. Make sure it doesn't go into hibernate or standby, because that will kill your battery over time.

 

If you're looking for a permanent install, rather than installing a bulky PC, why not buy a MacMini? It's a small little box that can be easily tucked almost anywhere in the car and then all you'll need is a compatible monitor. The power supply uses roughly 85 watts. Then to keep the mini computer from draining the car battery, you would use a relay that's inline to the on/ignition system for your car. The relay would cut off as well as provide power to your computer depending on whether the car ignition is off/on. Just make sure you properly shut down your computer before you turn the car ignition to off.

 

That's stupid. You'd need an inverter for one.. you need to convert the monitor signal and hope EDID information gets passed along correctly.. there's hardly anything available for CarPC software on the Mac OS.. you have to ghetto rig the startup and shutdown functionality.. and you're limited on hardware options and accessories for aftermarket development. Macs aren't good in any case unless you're on a college campus in the liberal arts department trying to look like a hipster.

 

Wiretap, thank you a lot for your help and everyone else who provided input. I think I have it pretty much figured out with all the help I have received I already have the custom box built and computer pretty much assembled now I just have to order my M4 psu and lilliput and everything will be on hand. The project is for a class im taking but I probably wouldn't do the install anyways till it gets warm again. I will post pictures once the project is done. Again guys thanks and stay tuned.