1. What size are the batteries?
2. 6 volt or 12 volt?
3. How many batteries?
4. Do you know the brand and model of your Inverter/Charger? Most Amercan Eagles have this type charger/Inverter system.
If you have the battery disconnect OFF and the batteries drain dead in less than 12 hours(overnight) you have to have a massive 12 volt draw. Now, if you have an Inverter/Charger, THAT appliance is NOT turned off by a battery disconnect and if that Inverter is ON, that would drain some battery systems overnight. Doug