Originally Posted by jcanavera
There have been some warnings in the past about always having a battery in place since going from the Univolt directly without a battery load may cause higher voltages and thus shorten 12 volt
True for old converters. They need a minimum load in order to regulate (I use the word loosely--the old coverters weren't very precise in their voltage control even under the best conditions) their output voltage. You won't have a problem with things like water pump or fridge (if yours uses 12V) because their load is sufficient. However, small things like a single light, or maybe a radio, provide such a small load that they might see 16-18 volts if they are the only thing turned on at the time. Not great for a light bulb.
The other problem is that without a load there will probably be significant ripple imposed on the dc voltage. You'll hear this as hum when you have the radio on and the peak voltage could be bad for electronic items and the min voltage is bad for motors.
Bottom line is that everything should work, but cross your fingers regarding silent damage and early light bulb burnout. I'd do it in a pinch, but avoid it for the long run.
Modern converters, like the Intellipower, are well regulated and put out a max of 13.9 volts, which is perfectly OK for 12V