US-12627160-B2 - Lithium ion battery cell balancing system and method, and a battery charging device with lithium ion battery cell balancing

US12627160B2US 12627160 B2US12627160 B2US 12627160B2US-12627160-B2

Abstract

Provided is a lithium ion rechargeable battery charging system with lithium cell balancing, including a lithium ion rechargeable battery and a battery charging device configured for charging the lithium ion rechargeable battery and wherein cell balancing of the lithium ion rechargeable battery cells of the lithium ion rechargeable battery continues for a predetermine period of time once a cell balancing mode begins.

Inventors

James P. McBRIDE
Daniel L. Simon
James Richard Stanfield

Assignees

THE NOCO COMPANY

Dates

Publication Date: 20260512
Application Date: 20210602

Claims (8)

1 . A lithium-ion rechargeable battery charging system with lithium cell balancing, the system comprising: a lithium-ion battery comprising a plurality of battery cells connected together in electrical series and a battery management system (BMS), the battery management system (BMS) including a discharge switching circuit and a charge switching circuit, the BMS being configured to close the charge switching circuit to begin charging the lithium-ion battery from a battery charger, monitor a voltage of each of the plurality of battery cells in the lithium-ion battery, and upon determining that a voltage of one or more of the plurality of battery cells rises above an overvoltage threshold, open the charge switching circuit to stop charging the lithium-ion battery, connect one or more resistive loads to the one or more of the plurality of battery cells with a voltage above the overvoltage threshold, and close the discharge switching circuit to enable voltage from the one or more of the plurality of battery cells with a voltage above the overvoltage threshold to be discharged through the one or more resistive loads, wherein a voltage of the lithium-ion battery is detected to determine that the lithium-ion battery has not become disconnected from the battery charger when the charge switching circuit is opened by the BMS, wherein the voltage of the lithium-ion battery is periodically polled to determine when the BMS closes the charge switching circuit to continue charging the lithium-ion battery; and wherein upon a determination that a combined voltage of the plurality of battery cells has reached a threshold voltage, the plurality of battery cells transitions to being charged in a constant voltage charging mode to maintain a taper charge of the plurality of battery cells, the constant voltage charging mode emulated using a constant current battery charger by turning a charging current on and off to maintain the combined voltage of the plurality of battery cells within a voltage range.
2 . The system of claim 1 , wherein the voltage of the lithium-ion battery is detected across a diode of the charge switching circuit.
3 . The system of claim 2 , wherein the charge switching circuit includes a charge FET coupled in parallel with the diode.
4 . The system of claim 1 , wherein the discharge switching circuit includes a discharge FET coupled in parallel with a diode.
5 . The system of claim 1 , wherein the BMS is further configured to, upon determining that the voltage of one or more of the plurality of battery cells is at or under a safe threshold voltage, disconnect the one or more resistive loads from the one or more of the plurality of battery cells, open the discharge switching circuit, and close the charge switching circuit to continue charging the lithium-ion battery.
6 . The system of claim 1 , wherein the threshold voltage is 14.6 volts.
7 . The system of claim 1 , wherein the taper charge is maintained for a set period of time before charging is stopped.
8 . The system of claim 1 , wherein the voltage range is between 14.4 volts and 14.6 volts.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a National Stage Entry of International Patent Application No. PCT/US2021/035328, filed on Jun. 2, 2021, which claims the benefit of priority to U.S. Provisional Application No. 63/033,717, filed on Jun. 2, 2020, each of which is hereby incorporated by reference in its entirety for all purposes FIELD The present invention is directed to a lithium ion battery cell balancing system and method, and a battery charging device comprising a lithium ion battery cell balancing system and/or incorporating the lithium ion battery cell balancing method according to the present invention. BACKGROUND Currently, there exists a battery charger for charging a depleted or discharged lithium ion rechargeable battery (e.g. depleted or discharged lithium ion rechargeable vehicle battery). The existing battery charger operates in a manner that if the lithium ion rechargeable battery voltage of the battery charger reaches a cut-off voltage for a Lithium mode (e.g. 14.6V) while the battery charger is delivering current to the depleted or discharged lithium ion rechargeable battery being charged, even during a soft start, the charge current is cut-off and a fuel gauge on the display of the battery charger displays a solid green light (e.g. via a green LED in the fuel gauge), after an appropriate fuel gauge time increment. Further, the existing battery charger will oscillate between a lithium mode and a stand-by mode during charging operation of the depleted or discharged lithium ion rechargeable battery. Specifically, when charging a lithium ion rechargeable battery with a Battery Management System (BMS) and the lithium ion rechargeable battery cells are unbalanced, the battery charger will oscillate between the lithium mode and the stand-by. This is caused because the lithium ion rechargeable battery's Battery Management System (BMS) monitors each cell voltage. If a lithium ion rechargeable battery cell gets charged too high, the Battery Management System (BMS) will open the Charge FET to prevent further charging of the particular lithium ion rechargeable battery cell. Meanwhile, an internal resistor in the Battery Management System (BMS) is connected to slowly discharge the lithium ion rechargeable battery cell. The Charge FET will again be closed once the over-voltage lithium ion rechargeable battery cell has discharged to a lower level. When the Charge FET opens up, a diode is still present which allows a discharge path to the lithium ion rechargeable battery cells. This means that when the battery charger is connected to the lithium ion rechargeable battery, an internal voltage divider resistor network in the battery charger will still sense a voltage at the terminals, and try to drive a charge current. Since the Charge FET in the battery is open, no current is sensed by the charger, and the charger then goes back to Stand-by mode. Since the battery charger detects the battery voltage, it pols the battery voltage every few seconds to see if a current can be applied. When trying to apply the current, the battery charger goes from Stand-by mode to Lithium mode. The battery charger will oscillate between stand-by mode and Lithium mode until the battery BMS closes the Charge FET. SUMMARY The present invention is directed to a lithium ion battery cell balancing system and/or method for charging a depleted or discharged lithium ion rechargeable battery, and a battery charger comprising the lithium battery cell balancing system and/or incorporating the lithium ion battery cell balancing method according to the present invention. The lithium ion battery cell balancing method comprises or consists of a number of steps for balancing the multiple lithium ion rechargeable battery cells of the lithium ion rechargeable battery, depending on the particular type of battery charger (e.g. Constant Current (CC) type battery charger or Constant Voltage (CV) type battery charger). The presently described subject matter is also directed to a lithium ion rechargeable battery charging system and/or method for use in a battery charger configured to charge a lithium ion rechargeable battery that has a built in Battery Management System (BMS). The lithium ion rechargeable battery comprises multiple lithium ion rechargeable battery cells connected together in an electrical series arrangement. The lithium ion rechargeable battery cells can become imbalanced relative to each other due to variations in capacities or loads on the various lithium ion rechargeable battery cells. Specifically, during charging operation the voltages of the lithium ion rechargeable battery cells become different relative to each other. To keep the lithium ion rechargeable battery cells operating in a safe voltage range, the lithium ion rechargeable battery can include a Battery Management System (BMS). The role of the Battery Management System (BMS) is to monitor the voltages of the lithium ion rechargeable battery cells