Maxim Model Gauge M5 Fuel Gauges from the MAX172XX famly can be used with Lithium Thionyl Chloride batteries, but not all the features can be utilized. The M5 algorithm uses coulomb counting to track charge consumption, and uses voltage measurements to improve long-term accuracy to correct for the small offset error in the current measurements. Because the Lithium Thionyl Chloride chemistry has a flat discharge curve, there is no useful correlation between voltage and state of charge (SOC) over the majority of the discharge profile. For this reason, only the coulomb counting data is useful. This simplifies the design process because no battery model is needed, and to measure SOC, simply read the QH register to see how much charge has been consumed.