What is the lowest voltage level before recharging without starting to cause damage to the battery? Some sites suggest 50% charge. Do you have a state of charge chart. This is for an travel trailer application.

A reading of 12.66 volts indicates a fully charged battery. If the reading is 12.45 volts or less, the battery is low and needs to be recharged. In regards to sealed AGM batteries, it is recommended to not let them go below 50% of full charge range.