depends on your vehicle and how healthy your battery is. I think the average is 10v.
I am looking at using a inverter and it can go as low as 10.5 before going into "battery save" mode and shutting off. Is this low enough to survive crank? I searched for an idea of how low the voltage goes but was only able to find something in the FAQ section about minimum input being as low as possible for a PUS, no set number.
depends on your car and the battery you have. There is no simple answer to your question. Just try it and find out.
dammit, I lose
It seems to me that it would depend on the car?
From what people are telling me it's just better to use a DC PSU... I had the same idea you did untill I found a cheaper DC PSU... for the cost of an inverter and normal PSU, it would equal or be more expensive than a ~$50 DC-DC PSU and shutdown controler... then you don't have to worry about cranking or anything.
Worst case about 8V. Typical with oldish battery etc 9-10V. Higher for a good big battery. Also depends if you ahve diesel. The glow plugs and then starting using compression drags the voltage down i believe.
I have a 2004 WRX and new battery, I already have a spare PSU, I have looked at the DC PSUs but I have not found a 300w one yet and am pursuing this route, unless you guys have a link to a PSU that big.