Battery capacity, battery capacity and power consumption are unknown. Assume that the battery is fully charged (power consumption is more than 90%), the current consumption is 5 amps, and the battery is 60AH.

1, discharge to 50%, start the car smoothly, 60*(90%-50%)/5=4.8 hours.

2. When the battery is discharged to 20%, keep the battery powered off, 60*(90%-20%)/5=8.4 hours.

3. When all the power is discharged, the battery life will be reduced by 80%, 60*90%/5= 10.8 hour.