I got me an inverter to use this monitor with my Bescor battery, but I don't know how long it'll last unless I know how much wattage the monitor draws. I can't find anything on the back of the monitor, on Sony's site, or anywhere else. Any ideas? Please help.

Josh
That is a 14" 600 line monitor and rated at 90 watts. Had you bought an 8 or 9" field monitor the wattage would have been 40 - 50 watts and in all probability it would have a 12volt DC feed. Assuming no loss through the inverter(and there will be loss), that monitor will draw 7.5 amps or to run one hour 7.5 amp hours. To factor in the loss of the inverter it's just a guess but i'd say you'd need a fully charged 10 amp hour battery to get 1 hour.operation.

http://bssc.sel.sony.com/Professional/docs/brochures/sonymonitorlineupguide.pdf

Not to sound stupid, but I have no idea what most of that means. Thanks for the advice though. I'm guessing I'll have somewhere between 35 and and 50 minutes with it.

If it is a 7 amp hour i'm guessing 45-50 min.

Thanks.

Why not get a cordset to run from your car battery. Your inverter should be equiped with a cig lighter adapter. What is the wattage of your inverter?
From the inverter just run a standard extension (no longer than nec)

How long do I have before I screw up my car this way, though?

2-3 hours wouldn't even stress the new batteries.