When I Google it I get this: "LoZ stands for Low Impedance (Z). This feature presents a low impedance input to the circuit under test. This reduces the possibility of false readings due to ghost voltages and improves accuracy when testing to determine absence or presence of voltage." Looks like this is a feature on some of the better multimeters like Fluke...although my old Fluke doesn't have it. That aside, 12.3 volts on a fully charged battery isn't acceptable. It should be 12.7 and higher. 12.4 on one that's been sitting static a while. If your meter is right...I think there is something wrong with that battery. Take a reading on another 12 volts battery...like yours car or truck.