low voltage cutoff vs AMP hours used at high amp draw

I have 2x GPL-6CT in my airstream, when I use my convection/micro it draws at 130 amps or so. In theory, I can can run my convection/micro for over an hour before I reach 50% discharge on my battery bank. My Magnum inverter has a low voltage cuttoff settings, to save the batteries which can be set down to 9 Volts.



In practice, I can run the micro for about 35-45 minutes before the voltage is below 9 Volts at a 130amp draw. The moment the micro is turned off, I am at 70% battery and back above 12 volts.



So... does this damage the batteries? Battery is not low based on amp hours, but the voltage is low due to the load.



Thanks,

-Dwight