I borrowed a 100 amp hour battery and inverter from Interstate Battery so I could test out the sound system to see how long the battery would last. For the off-the-grid concert, I will need 5-6 hours of power. This first test went well. Since I was using the sound system in my house, I did not turn up the volume as loud as will be necessary for the concert. However, I am optimistic that a solar panel or bicycle generator will be able to charge the battery sufficiently to maintain power for the enire length of the concert.
During the battery test, I measured and recorded the voltage of the battery every 30 minutes.
Start: 12.83 v
30 min: 12.73 v
1 hour: 12.72 v
1.5 hour: 12.71 v
2 hours: 12.70 v
2.5 hours: 12.69 v
3 hours: 12.67 v
3.5 hours: 12.65 v
4 hours: 12.63 v
4.5 hours: 12.62 v
5 hours: 12.60 v
5.5 hours: 12.58 v
6 hours: 12.56 v
The battery would be considered to be 75% charged at 12.65 volts and 50% charged at 12.45 volts. Thus, after 6 hours, the battery was still over 50% charged.
Start: 12.83 v
30 min: 12.73 v
1 hour: 12.72 v
1.5 hour: 12.71 v
2 hours: 12.70 v
2.5 hours: 12.69 v
3 hours: 12.67 v
3.5 hours: 12.65 v
4 hours: 12.63 v
4.5 hours: 12.62 v
5 hours: 12.60 v
5.5 hours: 12.58 v
6 hours: 12.56 v
The battery would be considered to be 75% charged at 12.65 volts and 50% charged at 12.45 volts. Thus, after 6 hours, the battery was still over 50% charged.