How much gas does your genny use? And a charging question

I find it odd the charging took 3x as long as at home. More likely the battery was lower on charge than you think. Did you monitor the charge to verify it was not shutting down intermittently? Need an ammeter to verify the charger is working same on inverter vs. utility power. Most don't charge to 100% while camped because the last 10% does take an extended period.