System and method for measuring lithium-ion state-of-charge
AssigneeHella GmbH & Co. KGaA
InventorBrian James Stockford
Life of this patent
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Abstract
A system and a method for measuring a state-of-charge of a lithium-ion battery are provided. The system and the method include first and second capacitive electrodes that are applied to the exterior of a pouch-type battery cell or a battery stack, the capacitive electrodes defining a capacitive coupling. The system and method further include measuring the capacitance of the capacitive coupling and correlating the capacitance with a state-of-charge of the lithium-ion battery. The capacitively-derived state-of-charge measurement can be used in combination with a voltage-derived state-of-charge measurement, thereby providing a redundant state-of-charge determination. Other applications include low battery warnings and end-of-life warnings.
Claims15
An electrical system comprising:
- a battery stack comprising a plurality of lithium-ion battery cells, each of the plurality of lithium-ion battery cells including a battery pouch that sealably encloses a cathode, an anode, and a separator, the separator being disposed between the cathode and the anode;
- first and second isolator plates disposed on opposing ends of the battery stack, wherein expansion of the plurality of lithium-ion battery cells causes the first and second isolator plates to move outwardly relative to each other;
- and
- first and second capacitive electrodes that are movable with the first and second isolator plates, respectively, such that the first and second capacitive electrodes define a capacitance that varies during discharging and recharging of the plurality of lithium-ion battery cells.
A method for measuring the state-of-charge of a lithium-ion battery cell including a battery pouch that sealably encloses a cathode, an anode, and a separator, the method comprising:
- providing first and second capacitive electrodes that are movable in response to expansion of the battery cell;
- measuring a capacitive coupling of the first and second capacitive electrodes during charging or discharging of the battery cell;
- and
- determining a state-of-charge percentage of the battery cell based on the measured capacitive coupling of the first and second electrodes.
An electrical system comprising:
- a battery cell including a battery pouch that sealably encloses a cathode, an anode, and a separator, the separator being disposed between the cathode and the anode;
- first and second capacitive electrodes joined to first and second exterior surfaces of the battery cell, the first and second capacitive electrodes defining a capacitive coupling;
- and
- a measurement circuit coupled to the first and second capacitive electrodes, the measurement circuit being adapted to (a) measure the capacitive coupling of the first and second capacitive electrodes during discharging or recharging of the battery cell and (b) determine a state-of-charge percentage of the battery cell based on the measured capacitive coupling of the first and second capacitive electrodes.
Dependencies are inferred from the claim text.