Podmods, Maintenance, Tips and Tricks : Parasitic battery drains

We just purchased 2 new 6 volt golf cart batteries. After installing them, we drove for about an hour with the truck charging them. After using them for 1 day, the meter showed they were down to 12.2 volts. We used no lights(all solar powered lanterns), the furnace came on twice and the refrigerator was on propane. The only parasitic loads that I know of was the propane detector. We have no entertainment system. I do have a 400 watt inverter directly connected to the battery, but it was not in use. We did not use the water pump. We have a 20 watt PWM solar controller installed but we did not use it.

Does anybody have an idea why the batteries were weakened so quickly?

Thanks

Vann