Quote: Originally Posted by
capcadetjc 
So what your saying is that that setup wont run well right? I hope I haven't caused any trouble, just trying to help. Could you send me in the right direction for a read me of this DC-DC. Ive never heard of it.
DC-DC is short for a DC-DC Power Supply.
And inverter goes DC to AC. Then a power supply (PSU) goes AC to DC. So when running a computer off of an inverter in the car, you are going DC - AC - DC. Each covnersion is innefficient, wastes energy, gives off heat, and the DC to AC portion (the inverter) introduces nasty spikes into your car's electrical system most noticeable in audible hums or video flickering. This interference is being transfered to the electronics you are powering too. Electronics dont like that, and will die earlier because of it.
The signal coming out of those cheapo inverters is not a sine wave like coming out of your house. It is a sqaure wave or triangle wave usually. This is very messy and doesnt provide the correct power needed to charge a large battery. Hence why the UPS will never charge. You can buy a true sine wave inverter and it will work fine. But those are usually in excess of $300 for small ones.
A DC-DC on the other hand just converts the 12v-14.4v of your car to computer PSU voltages at specified voltages. Usually include Shut Down Controllers (SDC) as well.