Abstract: A method of determining state of charge of an energy delivery device includes sampling voltage values of the energy delivery device during relaxation of the device. The method further includes regressing an open circuit voltage value and the total overpotential being relaxed. The regression includes a predetermined time constant of relaxation associated with the energy delivery device. One embodiment uses the equation V(t)=OCV?? exp(?t/tau), where V(t) represents the sampled voltage values, t represents times at which each of the voltage values are sampled, OCV represents the open circuit voltage value of the energy delivery device, ? represents the overpotential value, and tau represents the time constant of relaxation. The method uses a predetermined profile that relates open circuit voltage of the energy delivery device to state of charge of the device, to determine a particular state of charge corresponding to the regressed open circuit voltage value.

Abstract: Electroactive compositions are disclosed for use in lithium ion battery electrodes. The compositions, such as multifunctional mixed metal olivines, provide an electrochemical cell having a plurality of open circuit voltages at different states of charge. The compositions afford improved state-of-charge monitoring, overcharge protection and/or overdischarge protection for lithium ion batteries.

Abstract: A battery management system includes one or more lithium ion cells in electrical connection, each said cell comprising: first and second working electrodes and one or more reference electrodes, each reference electrode electronically isolated from the working electrodes and having a separate tab or current collector exiting the cell and providing an additional terminal for electrical measurement; and a battery management system comprising a battery state-of-charge monitor, said monitor being operable for receiving information relating to the potential difference of the working electrodes and the potential of one or more of the working electrodes versus the reference electrode.

Abstract: Porous separators for use in electrochemical cells and methods of their manufacture are provided. The separators are porous structures comprising an electroactive material and an electronically insulating structural material, wherein the electroactive material forms a percolating path in the separator.