In an example, a solid-state battery apparatus is provided. The apparatus has a plurality of battery cell devices, each of the devices having an anode device, an electrolyte device, and a cathode device. The apparatus has an equivalent circuit (EC) numbered from 1 through N characterizing the plurality of battery cells devices, a state of charge characterizing the plurality of battery cell devices, and a resistor, capacitor, or other electrical parameters provided in the equivalent circuit.