Battery phase meter to determine internal temperatures of lithium-ion rechargeable cells under charge and discharge

A system to measure an internal temperature of a lithium-ion rechargeable cell, comprising:

• an alternating signal source to apply an alternating signal to the cell to generate a phase-shifted alternating signal at the cell;
• a phase meter to detect the phase-shift as a phase difference between a frequency of the applied alternating signal and a frequency of the phase-shifted alternating signal;
• and
• a phase-to-temperature converter to determine the internal temperature of the cell based on the phase difference;
• wherein the alternating signal source includes one or more of an alternating current source to generate a phase-shifted alternating voltage, and an alternating voltage source to generate a phase-shifted alternating current.

A method of correlating a phase delay of a rechargeable lithium-ion cell with an internal temperature of the cell, comprising:

• applying an alternating signal to the cell when the internal temperature of the cell is at a first temperature to generate a phase-delayed alternating signal at the cell;
• detecting a phase difference between a frequency of the applied alternating signal and a frequency of the phase-shifted alternating signal;
• repeating the applying and the detecting for one or more additional internal temperatures of the cell;
• correlating the phase differences with the temperatures;
• and
• recording the correlations in a tangible medium;
• wherein the applying includes one or more of applying an alternating current to generate a phase phase-shifted alternating voltage, and applying an alternating voltage to generate a phase phase-shifted alternating current.

A method of identifying a thermal condition of a lithium-ion cell, comprising:

• applying an alternating signal to the cell to generate a phase-shifted alternating signal at the cell;
• detecting the phase shift as a phase difference between a frequency of the applied alternating signal and a frequency of the phase-shifted alternating signal;
• and
• initiating a pre-emptive action to prevent thermal runaway when a rate of change of the phase-difference meets or exceeds a threshold rate, wherein the applying and the detecting are performed continuously or periodically.