Depends on the converter that you have. Some can handle not having a battery in the circuit, some can't. Look up the info on your converter and see what it says.
If you do leave a battery hooked up, make sure you check the voltage and battery water frequently or you may need a new one after a few months, as it may lose water with the constant float voltage and dry up and be ruined.
2007 Chevy 2500HD Classic LBZ Duramax/Allison (Stock)
2005 Bigfoot 1500C8.2 AWESOME