Hybrid battery system with multiple discharge voltage plateaus and greater charge capacity of metal in the negative electrode

The hybrid battery system has multiple discharge voltage plateaus and a greater charge capacity of metal in the negative electrode, while still having sufficient energy density and sufficient power capability to supply external devices. The charge capacity of the negative side is higher than the charge capacity of the positive side. There are two solvent compositions in the cathodic solution, and there is a transition from a first discharge voltage plateau to a second discharge voltage plateau at a voltage less than the first discharge voltage plateau. The battery system is safe, and the transition between discharge voltage plateaus provides an estimation of battery capacity that can indicate when the battery system is running out of power.