[Al Skierkiewicz]

I have it on good authority that the 24 volt voltage convertor that is intended to power the CRIO stops functioning when the input voltage is 4.5 volts or less. Make that 5 or 6 volts to be sure and you should be alright. A dead battery could register a very low terminal voltage under load and then return to 12 volts with no load on the battery. That is why, I don't recommend using a voltmeter to check for battery charge condition.