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I'm trying to build a PC for my car and I need to build a battery in it to allow it to run when the car is off, but to suspend after a given amount of time. The goal is to build a pretty small, fully-integrated computer. Is there a way to build a battery into a Mini ITX case, or do I need an external battery?

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up vote 1 down vote accepted

It really depends on the case you have.

I would personally get one of solid state picoPSU things and power the PC through a battery. Charge up a capacitor while the car is running, then when the car shuts off let it slowly drain through a resistor to ground and when the capacitor is empty get a mosfet to poke the "power button" pins for it to go into automatic powerdown

Note: I would try to avoid going DC(car) to AC(inverter/UPS) to DC(pc) as you'll loose alot of power that way and inverters always pull power even if they are not powering anything

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Should I run a battery separate from my car's main battery? I was assuming that I should simply allow charging and power drain while the car is running and simply cut all power to the PC when it's off, letting the PC use a battery. Also, how complicated is it to set up a capacitor/resistor? I'm kind of new at this :-| – Naftuli Tzvi Kay May 8 '12 at 21:04
I used to use a separate battery, you also need something to limit the voltage from the car while its running.. itll be 16-18v which is too high.. The capacitor resistor thing is pretty simple.. you could probably also do something with an LM555 timer.. but I havnt tried that – madmaze May 8 '12 at 21:25

I think, given the sheer form factor of a M-ITX case you would be better off getting some soft of UPS that is plugged into the car battery and working out how to do a graceful shutdown if the ignition has been cut for more than x minutes. You could try and bodge a load of batteries into a hard disk space but that probably wouldn't be a high enough current/voltage to power a PC.

Also consider a laptop. Inbuilt battery. See if you can find a model that can also take an external secondary battery.

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