Lithium-ion battery cell balancing system, method for the same, and battery charging device including lithium-ion battery cell balancing

Abstract

To provide a lithium-ion rechargeable battery charging system including lithium cell balancing and a lithium cell balancing method.SOLUTION: A battery charging device 10 includes a plurality of lithium-ion rechargeable battery cells 26A to 26D connected in series and a battery management system (BMS). The BMS includes a discharge field effect transistor (FET) 30 and a charge FET 32. A lithium-ion rechargeable battery charging system including a lithium cell balancing mode includes a lithium-ion rechargeable battery and a battery charging device 20 configured for charging the lithium-ion rechargeable battery. Cell balancing of the lithium-ion rechargeable battery cell of the lithium-ion rechargeable battery continues for a predetermined time from the start of the cell balancing mode.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a lithium-ion battery cell balancing system and method, and to a battery charging device comprising a lithium-ion battery cell balancing system and / or incorporating the lithium-ion battery cell balancing method of the present invention. [Background technology]

[0002] Currently, there are battery chargers for charging depleted or discharged lithium ion rechargeable batteries (e.g., depleted or discharged lithium ion rechargeable vehicle batteries). The mode of operation of these existing battery chargers is that while the battery charger is providing current to a depleted or discharged lithium ion rechargeable battery being charged, if the lithium ion rechargeable battery voltage of the battery charger reaches the lithium mode cutoff voltage (e.g., 14.6V), even during soft start, the charging current is cut off and the fuel gauge on the battery charger's display displays a solid green light (e.g., via a green LED on the fuel gauge) after an appropriate fuel gauge time increment.

[0003] Additionally, existing battery chargers cycle between lithium mode and standby mode while charging a depleted or discharged lithium ion rechargeable battery. Specifically, when a lithium ion rechargeable battery is being charged by a Battery Management System (BMS) and the lithium ion rechargeable battery cells become unbalanced, the battery charger cycles between lithium mode and standby mode.

[0004] This is because the Battery Management System (BMS) of a Lithium-Ion rechargeable battery monitors the voltage of each individual cell. If a Lithium-Ion rechargeable battery is charged to an excessively high voltage, the Battery Management System (BMS) opens the charge FET to prevent further charging of that 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. Once the Lithium-Ion rechargeable battery cell with the excessive voltage is discharged to a low level, the charge FET is closed again.

[0005] When the charge FET is open, there is still a diode providing a discharge path for the Lithium-Ion rechargeable battery cell. This means that when the battery charger is connected to a Lithium-Ion rechargeable battery, the battery charger's internal voltage divider resistor network will sense the voltage at the terminals and attempt to drive the charging voltage. Because the battery's charge FET is open, no current is detected by the battery charger and the battery charger goes back into standby mode.

[0006] The battery charger senses the battery voltage, so every few seconds the battery charger gets the battery voltage and checks if it can supply current. When it is ready to supply current, the battery charger goes from standby mode to lithium mode. The battery charger cycles between standby mode and lithium mode until the Battery Management System (BMS) closes the charge FET. Summary of the Invention

[0007] The present invention relates to a lithium-ion battery cell balancing system and / or method for charging depleted or discharged lithium-ion rechargeable batteries, a battery charger comprising a lithium-ion battery cell balancing system and / or incorporating a lithium-ion battery cell balancing method according to the present invention.

[0008] The lithium-ion battery balancing method includes multiple steps for balancing multiple lithium-ion rechargeable battery cells of a lithium-ion rechargeable battery depending on the type of battery charger (e.g., a constant current (CC) type battery charger or a constant voltage (CV) type battery charger).

[0009] The subject matter described herein also relates to methods for use in lithium-ion rechargeable battery charging systems and / or chargers integrated into a battery management system (BMS) and configured to charge lithium-ion rechargeable batteries.

[0010] A lithium ion rechargeable battery comprises a number of lithium ion rechargeable battery cells arranged electrically in series with one another. The lithium ion rechargeable battery cells may become unbalanced with one another due to differences in the containers and loads of the various lithium ion rechargeable battery cells. Specifically, during a charging operation, the voltages of the lithium ion rechargeable battery cells differ relative to one another.

[0011] To keep the lithium-ion rechargeable battery cells operating within a safe voltage range, the lithium-ion rechargeable battery may be equipped with a battery monitoring system (BMS), the role of which is to monitor the voltage of the lithium-ion rechargeable battery cells and open the discharge FET when any lithium-ion rechargeable battery cell of the lithium-ion rechargeable battery becomes undercharged, and open the charge FET when any lithium-ion rechargeable battery cell of the lithium-ion rechargeable battery becomes overcharged.

[0012] A battery management system (BMS) may include a lithium ion rechargeable battery cell balancing function according to the present invention. The battery management system (BMS) may monitor the voltage of each individual lithium ion rechargeable battery cell within the lithium ion rechargeable battery. If a particular lithium ion rechargeable battery becomes overcharged, the battery management system (BMS) places a small resistive load on the particular lithium ion rechargeable battery cell to slowly drain the charge from the particular lithium ion rechargeable battery cell. When the voltage of the particular lithium ion rechargeable battery cell drops to a safety threshold, the resistive load on the particular lithium ion rechargeable battery cell is removed.

[0013] During cell balancing of a lithium-ion rechargeable battery with unbalanced lithium-ion battery cells, the Battery Management System (BMS) will open and close multiple times, causing the Battery Management System (BMS) to slowly balance the internal lithium-ion rechargeable battery cells.

[0014] For charging a lithium-ion rechargeable battery, the final step is to remain in constant voltage (CV) mode and maintain a taper charge threshold at the battery charger terminals to allow time for the lithium-ion rechargeable battery's internal Battery Management System (BMS) to balance the cells. This time is called the lithium cell balance time and may be set to, for example, 4 hours. However, this time is programmable and may be adjusted to a different duration (e.g., 6 hours or 8 hours).

[0015] During the Lithium Cell Balance Time, the battery charger is in constant voltage (CV) mode. During this time, the battery charger must be able to identify if the BMS of the Lithium-Ion rechargeable battery has opened the charge FET or if the user has removed the charge cable from a depleted or discharged Lithium-Ion rechargeable battery that is being charged. If the charge FET is opened by the BMS, the battery charger must remain in Lithium Cell Balance Mode for balancing at the Lithium Cell Balance Time. If the user removes the battery charger from the Lithium-Ion rechargeable battery, the battery charger must go into standby mode.

[0016] While the lithium-ion rechargeable battery is in Lithium Cell Balance (LCB) mode, the output current of the battery charger is monitored. When the charging current drops below a minimum sense current level, the battery charger begins checking the battery voltage every second.

[0017] To check the voltage of the lithium-ion rechargeable battery, the battery charger opens the circuit from the battery charger's constant voltage supply to the lithium-ion rechargeable battery and measures the voltage of the lithium-ion rechargeable battery. If the voltage of the lithium-ion rechargeable battery drops below 10.5V, the user disconnects the battery charger cable from the lithium-ion rechargeable battery. If the voltage of the lithium-ion rechargeable battery is above 10.5V, the Battery Management System (BMS) opens the charge FET and the battery charger connects the battery charger's constant voltage source to the lithium-ion rechargeable battery until the next 1 second lithium-ion rechargeable battery voltage check time interval. If the lithium-ion rechargeable battery begins drawing a detectable current again, the internal switch remains closed.

[0018] It is important to note that the battery charger can still measure the voltage of the Li-Ion rechargeable battery (minus the diode drop) when the charge FET is open, because the freewheeling diode provides a current path for the measurement.

[0019] There are two modes of Lithium Cell Balancing (LCB). In the first Lithium Cell Balancing (LCB 1) mode when the Lithium-Ion rechargeable battery cells are not significantly out of balance, the Battery Management System (BMS) does not open the charge FET during the first Lithium Cell Balancing (LCB 1). In this mode, a constant current (CC) type battery charger emulates a constant voltage (CV) type battery charger. This is done by charging the Lithium-Ion rechargeable battery using a first soft start current level until it reaches 14.6V. At that point, the current is switched off and waits for the voltage to drop to 14.4V. Once the Lithium-Ion rechargeable battery is at 14.4V (with some delay), it switches back to the first soft start current and repeats. So essentially, a constant current (CC) battery charger emulates a constant voltage (CV) battery charger by maintaining the battery voltage within a narrow range of 14.4V to 14.6V.

[0020] In Secondary Lithium Cell Balance (2nd LCB) mode, the Li-Ion rechargeable battery is far out of balance and the Battery Management System (BMS) opens the charge FET. The battery charger must detect whether the charge FET is open or if the user has disconnected the terminal. Since an open charge FET has a body diode connection, the battery charger can still measure the battery voltage minus a diode drop. Thus, even if the Battery Management System (BMS) opens the charge FET, the battery charger can still measure a battery voltage greater than 10.5V and still say it has a Li-Ion rechargeable battery connected. Therefore, the battery charger must be able to detect when the charge FET has closed again. This is done by polling the impedance of the Li-Ion rechargeable battery every second. While polling, the battery charger attempts to apply a charge current. If the current is not accepted, it knows the charge FET is still open. When the charge FET is closed and the next charge poll is attempted, the battery charger sees that the Li-Ion rechargeable battery is accepting current and charging continues at the first soft start level until the battery reaches 14.6V or the Battery Monitoring System (BMS) opens the charge FET. Once 14.6V is reached, the first Lithium Cell Balancing (1st LCB) mode is entered. If the BMS opens, the second Lithium Cell Balancing (2nd LCB) mode is repeated.

[0021] This is accomplished by either a first lithium cell balancing (first LCB) mode, a second lithium cell balancing (second LCB) mode, or a combination that results in the first lithium cell balancing (first LCB) mode after the second lithium cell balancing (second LCB) mode for a set time of cell balancing (LCB) operation.

[0022] For the battery charger, a time of, for example, 4 hours is chosen, but this time is arbitrary. The total time required for the battery management system (BMS) to reach full cell balance depends on how far out of balance the lithium-ion rechargeable battery is and what size balancing load is used by the battery management system (BMS). Both of these factors are not observable to the battery charger. [Brief description of the drawings]

[0023] [Figure 1] Schematic diagram of a lithium-ion rechargeable battery with a battery management system (BMS). [Diagram 2] FIG. 2 is a plan view of the battery management system (BMS) showing the connection of the BMS to a lithium-ion rechargeable battery. [Diagram 3] FIG. 2 is a perspective view of a battery management system (BMS) showing the connection of the BMS to a lithium-ion rechargeable battery. [Figure 4-1] Graph showing a G2 7AH (amp hour) battery with 0.33AH (amp hour) discharge from cell 1. [Figure 4-2] Graph showing a G2 7AH (amp hour) battery with 0.33AH (amp hour) discharge from cell 1 (7AH at 0.33AH discharge from cell 1). [Figure 5-1] Graph showing a G2 7AH (ampere hour) battery with 0.33A delivered to cell #1 (multiple charge cycles) (7AH plus 0.33A of additional charge is added to cell 1). [Figure 5-2] Graph showing a G2 7AH (ampere hour) battery with 0.33A delivered to cell #1 (multiple charge cycles) (7AH plus 0.33A of additional charge is added to cell 1). [Figure 6-1] Graph showing the above chart zoomed in to the 40-45 hour time frame (7AH plus 0.33A extra charge added to cell 1). [Figure 6-2]Graph showing the above chart zoomed in to the 40-45 hour time frame (7AH plus 0.33A extra charge added to cell 1). [Figure 7] Graph showing G2 cold start battery charging profile (potential typical use) (7AH cold start battery after several months on the shelf) [Figure 8] Graph showing G2 short discharge to maintenance charge (balanced battery slightly discharged then charged at +100 hours maintenance). [Figure 9] Graph showing a zoomed in time frame of the charging log mentioned above (balanced battery slightly discharged + charged at 100 hours maintenance). [Figure 10] Graph showing G10 7AH full charge with 0.45AH removed from cell 1 (G10 Firmv K 7AH with 0.45AH discharged from cell 1). [Figure 11] Graph showing competitor Li-Ion battery charging profile (Genius 2 Firmware Rev R charging a BTLI12A270CW Lithium battery). [Figure 12] Graph showing competitor Li-Ion battery charging profile (Genius 2 Firmware Rev R charging ATZ-10). [Figure 13] Graph showing competitor Li-ion battery charging profile (ATZ-10 charging continuum. Charge until BMS does not open, then discharge and recharge. Note: BMS does not open on recharge, battery cells remain balanced). [Figure 14] A graph showing NOCO's Li-Ion battery charging profile (Genius 5 Firmware Rev R charging an ETX12A battery). [Figure 15] Graph showing NOCO Li-Ion battery charging profile (Genius 2 Firmware Rev R charging a NOCO NLP9). [Figure 16] Graph showing NOCO Li-ion battery charging profile (Genius 5 Firmware Rev R charging a NOCO NLP14). [Figure 17] A graph showing the charging profile of NOCO's Li-ion battery with Genius 2 Firmware Ver.S (Genius 2 Firmware Version 5 charging a 7AH Lithium with LCB - cell 2 unbalanced). [Figure 18] Graph showing the Genius 10 Firmware P charging profile for NOCO Li-ion batteries (G10 LCB Firmware Rev P 7AH 12V Lithium @ 25C Cell 1 Overcharge). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] 1, battery charging device 10 includes a positive battery cable 14 and a negative battery cable 16 connected to a lithium ion rechargeable battery 20. For example, positive battery cable 12 may be connected to a positive terminal 22 of lithium ion rechargeable battery 20 (e.g., using a positive battery clamp, not shown), and negative battery cable 14 may be connected to a negative battery terminal 24 of lithium ion rechargeable battery 20 (e.g., using a negative battery clamp, not shown).

[0025] The lithium ion rechargeable battery 20 includes four lithium ion rechargeable battery cells 26A, 26B, 26C, and 26D electrically connected in series with each other, a Battery Management System (BMS) 28A connected to the four lithium ion rechargeable battery cells 26A, 26B, 26C, and 26D, a discharge FET 30, and a charge FET 32. As shown in FIG 1, the discharge FET 30 and the charge FET 32 are electrically connected in series with the four lithium ion rechargeable battery cells 26A, 26B, 26C, and 26D.

[0026] 2, the battery management system (BMS) 28 includes a printed circuit board 34. The printed circuit board 34 includes a positive external battery terminal, or positive battery connection 34A, for an internal lithium ion rechargeable battery, a negative external battery terminal 34B, and an internal lithium ion negative battery terminal 34C.

[0027] As shown in FIG. 3, a battery management system (BMS) 28 is connected to the lithium-ion rechargeable battery 20 .

[0028] The battery charger 10 is configured and / or programmed in a particular manner to charge the lithium-ion rechargeable battery 20. For example, the battery charger 10 includes a lithium-ion rechargeable battery cell balancing mode or function (i.e., Lithium Cell Balance).

[0029] For example, the battery charger 10 operates as follows: If the lithium-ion rechargeable battery voltage reaches the lithium mode cutoff voltage (e.g., 14.6V) while the battery charger 10 is supplying current to a depleted or discharged lithium-ion rechargeable battery 20, even in soft-start mode, the battery charger 10 enters a Lithium Cell Balance (LCB) mode for, e.g., 4 hours. The Lithium Cell Balance (LCB) mode is indicated by the 25%, 50%, and 75% fuel gauge LEDs on the battery charger 10 display, along with the 100% LED illuminated (i.e., similar to some gravity optimization).

[0030] During the Lithium Cell Balance (LCB) mode, the battery charger 10 cuts off the charging current when the battery voltage reaches the cutoff voltage. The battery charger 10 continues to monitor the battery voltage, and when the battery voltage drops to 14.4V, the battery charger 10 resumes charging at the lowest soft-start current (e.g., 1 / 2 the lowest soft-start current if the temperature is below 0°C). The battery charger 10 cycles on and off multiple times as the battery voltage increases to 14.6V and then drops to 14.4V. The battery charger 10 turns off even if the battery voltage drops beyond 14.4V for a predetermined time interval (e.g., 1 minute) after reaching 14.6V before the battery charger 10 is allowed to turn on again.

[0031] After a predetermined time interval (eg, 4 hours) in the lithium cell mode, the battery charger 10 will stop charging and the fuel gauge on the battery charger 10 display will show 100%.

[0032] (Lithium cell balancing mode with BMS round trip) When charging a lithium-ion rechargeable battery (lithium mode), if the lithium-ion rechargeable battery's Battery Management System (BMS) opens but is unable to provide charging current before the battery voltage reaches 14.6 V, as indicated by the battery charger 10 measuring a voltage above the start voltage but below 14.6 V, the battery charger 10 will enter lithium cell balance mode and begin a 4 hour timer. The fuel gauge will then illuminate the green 100% LED.

[0033] The battery charger 10 continues to poll the voltage of the lithium-ion rechargeable battery, but instead of going into standby mode between polling attempts, the battery charger 10 remains in lithium cell balancing (LCB) mode and the fuel gauge displays a green 100% LED (e.g., the green operating LED alternates between bright and dark).

[0034] When the battery charger 10 is in this current balancing mode, the battery management system (BMS) opens and closes randomly. The battery charger 10 continues to poll the voltage of the Li-Ion rechargeable battery when the battery management system (BMS) closes the FET, and when the FET is closed, the battery charger 10 charges at the lowest soft start current (e.g., 1 / 2 the lowest soft start current below 0° C.).

[0035] When the internal lithium-ion battery cells of a lithium-ion rechargeable battery are equalized to a condition where the battery management system (BMS) is not opened and the battery voltage rises to 14.6V, the battery charger 10 operates as described above, except that the four-hour timer is not reset.

[0036] After four hours in cell balance mode, the battery charger 10 will stop charging and the fuel gauge on the display of the battery charger 10 will show 100%. If the battery charger 10 does not detect that the battery voltage has dropped below the start voltage, the battery charger 10 will go into standby mode.

Claims

1. 1. A lithium-ion rechargeable battery charging system with lithium cell balancing, comprising: A lithium ion rechargeable battery comprising a plurality of lithium ion rechargeable battery cells connected in series and a battery management system (BMS), the battery management system (BMS) comprising a discharge field effect transistor (FET) and a charge field effect transistor (FET); a battery charging device connected or connectable to the lithium ion rechargeable battery while the lithium ion rechargeable battery is being charged, and configured to charge the lithium ion rechargeable battery; Equipped with The battery management system (BMS) is configured to monitor voltages of the plurality of lithium ion rechargeable battery cells of the lithium ion rechargeable battery and open the charging field effect transistor (FET) when any of the lithium ion rechargeable battery cells become undercharged, and when any of the lithium ion rechargeable battery cells become overcharged while charging the lithium ion rechargeable battery by the battery charging device, The battery management system (BMS) is configured to monitor the voltage of each of the lithium-ion rechargeable battery cells of the lithium-ion rechargeable battery, and when one of the lithium-ion rechargeable battery cells becomes overcharged, the battery management system (BMS) places a resistive load on the particular lithium-ion rechargeable battery cell to slowly drain and turn off charging of the particular lithium-ion rechargeable battery cell, and the battery management system (BMS) removes the resistive load when the voltage of the particular lithium-ion rechargeable battery cell drops to a safety threshold while the lithium-ion rechargeable battery is being charged by the battery charging device.

11. A lithium ion rechargeable battery charging system with lithium cell balancing, wherein cell balancing of the lithium ion rechargeable battery cells of the lithium ion rechargeable battery continues for a predetermined period of time once a cell balancing mode is initiated.

2. 2. The system of claim 1, wherein the battery management system (BMS) is configured to open and close the lithium ion rechargeable battery cells multiple times such that the lithium ion rechargeable battery cells are balanced by the battery management system (BMS) when the lithium ion rechargeable battery is being charged by the battery charging device.

3. Charging of the lithium ion rechargeable battery is in a constant voltage mode while maintaining a taper charge threshold at the terminals of the battery charging device to allow time for the battery management system (BMS) to balance the lithium ion rechargeable battery cells. The system of claim 1 .

4. The time is a lithium ion cell balance time. The system of claim 3.

5. The lithium ion cell balance time is set to a fixed length of time. The system of claim 4.

6. The lithium ion cell balancing time is set to 4 hours. The system of claim 5.

7. monitoring a battery charging output current during the lithium-ion cell balance time, and when the charging current from the battery charging device to the lithium-ion rechargeable battery falls below a minimum detectable current level, the battery charging device repeatedly checks the voltage of the lithium-ion rechargeable battery after a predetermined period of time. The system of claim 5.

8. the battery charging device checks the voltage of the lithium ion rechargeable battery every second; The system of claim 7.

9. the battery charging device intermittently opens a circuit from a constant voltage source of the battery charging device to the lithium ion rechargeable battery and the battery voltage of the lithium ion rechargeable battery is measured. The system of claim 7.

10. when the battery voltage of the lithium ion rechargeable battery drops below 10.5V, a user disconnects the battery charging device from the lithium ion rechargeable battery and battery charging goes into standby mode; The system of claim 9.

11. When the lithium-ion rechargeable battery rises above 10.5V, a charge FET of the battery management system (BMS) opens and the battery charging device reconnects the battery charging device constant voltage source to the lithium-ion rechargeable battery until the next 1 second lithium-ion rechargeable battery voltage check interval, when the lithium-ion rechargeable battery begins to draw detectable current again, and an internal switch is held closed. The system of claim 8.

12. The battery charging device is capable of measuring the voltage of the lithium-ion rechargeable battery minus a diode drop when the charge FET is open, with a freewheeling diode providing a current path for this measurement. The system of claim 11.

13. If the lithium ion rechargeable battery cells are not far out of balance, the battery management system (BMS) does not open a charge FET during lithium ion cell balancing, and a first soft start current level is used to charge the depleted or discharged battery unit until the depleted or discharged battery is at 14.6V, at which point the battery management system (BMS) turns off and waits for the voltage of the lithium ion rechargeable battery to drop to 14.4V before the battery management system (BMS) returns to the first soft start current level, and so on. The system of claim 1 .

14. when the lithium ion rechargeable battery cells are out of balance to the extent that the battery management system (BMS) opens the charge FETs, the battery charging device checks the impedance of the lithium ion rechargeable battery every minute to determine when to close the charge FETs again and begin charging the lithium ion rechargeable battery until the lithium ion rechargeable battery reaches 14.6V at a first soft start charge level or the battery management system (BMS) opens the charge FETs; The system of claim 1 .

15. 1. A lithium cell balancing method for use in charging a lithium ion rechargeable battery comprising a plurality of lithium ion battery cells and a battery management system (BMS) including charge and discharge FETs using a battery charger, the method comprising: monitoring the voltage of lithium ion rechargeable battery cells, opening the discharge FET when any of the lithium ion rechargeable battery cells of the lithium ion rechargeable battery become undercharged, and opening the charge FET when any of the lithium ion rechargeable battery cells of the lithium ion rechargeable battery become overcharged; placing a resistive load on a particular lithium ion rechargeable battery cell to slowly drain and turn off the charge on that particular lithium ion rechargeable battery cell; disconnecting said resistive load when the voltage of said particular lithium ion rechargeable battery cell drops to a safety threshold; When the lithium ion rechargeable battery is being charged by the battery charging device, opening and closing the charge FET of the battery management system (BMS) a number of times such that the BMS balances internal lithium ion rechargeable battery cells; remaining in a constant voltage (CV) mode and maintaining a taper charge threshold at the terminals of the battery charging device for a predetermined lithium cell balancing time to allow the battery management system (BMS) of the lithium ion rechargeable battery time to balance the lithium ion rechargeable battery cells of the lithium ion rechargeable battery. Lithium cell balancing method.

16. The lithium cell balancing time is a fixed amount of time. The method of claim 15.

17. The lithium cell balancing time is a variable length of time. The method of claim 15.

18. The lithium cell balance time is programmable and adjustable to different lengths of time. The method of claim 15.

19. the battery management system (BMS) opening the charge FET and identifying when a user disconnects a charge cable from the lithium ion rechargeable battery being charged. The method of claim 15.

20. When the charge FET is opened by the battery management system, the battery charging device remains in the lithium cell balancing mode for the time of balancing the lithium cell balance, and when the user disconnects the battery charging device from the lithium ion rechargeable battery, the battery charging device goes into standby mode.

20. The method of claim 19.

21. the lithium ion rechargeable battery monitors the output current of the battery charger in the lithium cell balancing (LCB) mode, and when the charging current drops below a minimum detectable level, the battery charger begins repeatedly checking the voltage of the lithium ion rechargeable battery; The method of claim 15.

22. the battery charging device begins checking the voltage of the lithium ion rechargeable battery every second; 22. The method of claim 21.

23. To verify the voltage of the lithium-ion rechargeable battery, the battery charging device measures the voltage of the lithium-ion rechargeable battery after disconnecting the lithium-ion rechargeable battery from its constant voltage supply, if the voltage of the lithium-ion rechargeable battery drops below 10.5V, the user disconnects the battery charging cable from the lithium-ion rechargeable battery and the battery charger goes into standby mode, if the voltage of the lithium-ion rechargeable battery is above 10.5V, an internal switch is held closed until the next 1 second lithium-ion rechargeable battery voltage verification time interval when a charge FET of the battery management system (BMS) opens and the battery charging device reconnects the battery charging device constant voltage source to the lithium-ion rechargeable battery and the lithium-ion rechargeable battery begins drawing detectable current again.

23. The method of claim 22.

24. The battery charging device is capable of measuring the voltage of the lithium-ion rechargeable battery minus a diode drop when the charge FET is open, with a freewheeling diode providing a current path for this measurement.

24. The method of claim 23.

25. With multiple modes of lithium cell balancing; The method of claim 15.

26. the lithium cell balancing comprises a first lithium cell balancing mode of the battery management system (BMS) when the lithium ion rechargeable battery cells are not far out of balance, and a second lithium cell balancing mode when the lithium ion rechargeable battery cells are far out of balance to the extent that the battery management system (BMS) opens the charge FETs.

26. The method of claim 25.

27. During the lithium cell balancing mode, the battery management system (BMS) does not open the charge FET.

27. The method of claim 26.

28. During the first lithium cell balancing mode, a constant current (CC) type battery charger emulates a constant voltage (CV) type battery charger.

28. The method of claim 27.

29. a first soft start current level is used to charge the lithium ion rechargeable battery until the voltage reaches 14.6V, at which point the current is turned off to wait for the voltage to drop to 14.4V, and once the lithium ion rechargeable battery is at 14.4V with at least one delay, the first soft start current is returned and the constant current (CC) type battery charger repeats by maintaining the battery voltage within a narrow voltage range of 14.4V to 14.6V, thereby causing the constant current (CC) type battery charger to emulate a constant voltage (CV) type battery charger; 29. The method of claim 28.

30. In a second lithium cell balancing mode, the battery charging device detects if the charge FET is open or if the user disconnects the terminal, and the open charge FET has a body diode connection so that the battery charging device can measure the battery voltage minus a diode drop, and when the battery management system (BMS) opens the charge FET but the battery charging device measures a battery voltage above 10.5 volts, the battery charging device can detect that the lithium-ion rechargeable battery is connected, and then the battery charging device can detect when the charge FET is closed again.

27. The method of claim 26.

31. the impedance of the lithium-ion rechargeable battery is repeatedly polled to detect when the charge FET has re-closed; 31. The method of claim 30.

32. The impedance of the lithium ion rechargeable battery is polled every minute.

32. The method of claim 31 .

33. While polling the impedance of the lithium-ion rechargeable battery, the battery charging device attempts to apply a charging current, and if no current is being accepted, the battery charging device recognizes that the charge FET is still open, and when the charge FET closes, upon the next attempt by the battery charging device to apply the charging current, the battery charging device determines that the lithium-ion rechargeable battery is accepting the charging current and continues charging at a first soft start level until the lithium-ion rechargeable battery reaches 14.6V or the battery management system (BMS) opens the charge FET, at which point it enters the first lithium cell balancing mode, and when the battery management system (BMS) opens it repeats the second lithium cell balancing mode.

32. The method of claim 31 .

34. the polling of the lithium ion rechargeable battery is performed by a combination of the first lithium cell balancing mode, the second lithium cell balancing mode, or the first lithium cell balancing mode after the second lithium cell balancing mode for a defined time during the lithium cell balancing operation.

34. The method of claim 33.

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