Hello, all: This is a bit OT (because of the PC being used) but I believe that the application of the solution is timeless :-) Anyway, I want to run a "book" PC on 12v while I'm outside using the telescope (the PC will run the CCD camera setup). I gave some thought to simply using an AC inverter, but converting 12v to 120v AC and then back to PC power supply voltages seemed horribly inefficient. The power supply is rated 12v/5.5a and 5v/1a. It's an NLX-type motherboard, so the 12v is converted to 5v for various peripherals at the point of need. The 5v from the power supply is to support system standby mode only. I went hunting for DC-input PC-form-factor supplies but they're upwards of $200. I thought about directly connecting the battery to the PC and using a small DC-DC converter for the 5v, but the battery voltage isn't really 12v (it's more like 13.8v) so a regulator would be necessary. Any thoughts as to a simple, low-cost yet efficient solution? Rich