[WaltBennett]

First off, are you certain you have an inverter (inverts 12v DC to 120v AC)? Unless you've a residential refrigerator, you probably only have a converter (converts 120v AC to 12v DC), but the single car battery should have lasted longer anyway unless there was some sort of DC load on it (lights on, etc.)

Second, if you do have an inverter, a single battery of just about any group size won't last long if the inverter is on and supplying 120 volts to something. I've four big 6 volt batteries that will last something over 12 hours providing 120v through my inverter for moderate to light loads, but that's how I designed the system. (They get charged back up by either the solar panels or shore power.) I've heard of several folks that bought units with residential refers and moderate sized inverters that had issues with either insufficient batteries, insufficient inverter size, or both.