Accessory sockets on my Ford are always on. As a result, I ran out of battery several times because I forgot to unplug accessories. I was hoping this would solve the problem. It turns off when the battery voltage drops. But the voltage sensor is set so low that if it cuts out, you probably won't be able to start your car. And there is no setting to set the trigger point. The literature also indicates that the two external connections are intended for accessories. You can use all three accessory ports. You simply can't connect a cigarette lighter to external ports because they don't have high-temperature contacts.