I recently purchased a vintage 65 shasta which i equipped with a 12v trojan deep cycle agm battery and my friend gave me a used 500/1000 inverter for off-the-grid use. The battery is rated for 100 Ah. I charged with battery with a new schumacher charger to 14.3 amps. I tested the system by plugging a shop light into the converter with a 60 watt bulb and came back 8 hours later to find the bulb off and the battery down to 10% of capacity. This seemed odd so I recharged the battery and tested the system again and in one hour the 60 watt bulb had drained the battery 20%. Since the battery and tester seem to working fine the only explanation I can think of is that the inverter itself is draining the battery. Any other ideas???