New battery completely drained
The battery should be charged to full capacity. Then check the charging system to see if the alternator is charging when the engine is running. Battery voltage should be 12.0 - 12.4 when sitting with the engine off. Voltage should rise to 13.0 - 13.5 volts with the engine running. If it does not, you have a changing system problem. If the charging system is working, you may have left the lights on or there is something draining the battery.