If anyone was wondering, both the OPUS and CarNetix products attempt to protect the battery from deep discharge. There are 2 reasons this mechanism is suboptimal:
1. IMHO, the cutoff value is set too low (10.6 V). I am not sure there's enough crank amps available by the time the voltage hits that spot. (I have an Optima 51R yellow top).
2. Those units can only "hard" power off, losing system state. Hibernating is a much more elegant solution.