Method and apparatus for charging rechargeable cells

• US 9,793,733 B2
• Filed: 11/29/2012
• Issued: 10/17/2017
• Est. Priority Date: 11/30/2011
• Status: Expired due to Fees

• Current Assignee: H-Tech Ag
• Original Assignee: H-Tech Ag
• Inventors: Hempel, Jrg
• Primary Examiner(s): Garbowski, Leigh
• Application Number:
  US14/361,838
• Publication Number:
  US 20140327406A1
• Time in Patent Office: 1,783 Days
• Field of Search: None
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H01M 10/443 in response to temperature
• CPC Class Codes: H02J 7/00041 in response to measured battery parameters, e.g. voltage, current or temperature profile
• CPC Class Codes: H02J 7/0068 Battery or charger load switching, e.g. concurrent charging and load supply H02J7/0013 takes precedence
• CPC Class Codes: H02J 7/00711 with introduction of pulses during the charging process
• CPC Class Codes: Y02B 40/00 Technologies aiming at improving the efficiency of home appliances, e.g. induction cooking or efficient technologies for refrigerators, freezers or dish washers
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A method for charging rechargeable cells, in particular lithium ion cells. An apparatus for charging such cells. In order to specify a method for charging a lithium-based cell and an apparatus for charging a lithium-based cell, in which the capacitance of the cell is optimally used, the charging time is drastically shortened, the shelf life of the cell is extended and/or it is possible to increase the capacitance of the cell, a method is stated which includes the following steps, pulsed charging of the cell, wherein the charging current I_L exceeds the nominal charging current I_Lmax of the cell during the charging pulses; and the cell is discharged between the charging pulses using load pulses.

Claims

1. A method for charging a lithium-ion based rechargeable cell, comprising:

pulsed charging the cell, wherein a charging current I_L, during the charging pulses, exceeds a maximal nominal charging current I_Lmax of the cell by up to 5-times; and

discharging the cell between the charging pulses by load pulses, wherein the load pulses are shorter than the charging pulses, and

measuring a voltage U_z of the cell during each load pulse;

checking whether the measured voltage U_z of the cell is equal or greater than an end-of-charge voltage U_Lmax of the cell;

finishing charging of the cell after the measured voltage U_z of the cell at each of a predefined number of load pulses (n) corresponds to an end-of-charge voltage U_Lmax of the cell, wherein n is greater than or equal to 1,

wherein a level of the charging current I_L varies in consecutive charging pulses.

2. The method according to claim 1, wherein the charging current I_L, during the charging pulses, is more than 1.5 times the maximal nominal charging current I_Lmax of the cell.

3. The method according to claim 2, wherein the charging current I_L is twice the maximal nominal charging current I_Lmax or greater.

4. The method according to claim 1, wherein a level of the charging current I_L, during the charging pulses and/or a height of the load pulses is dependent on a state of the cell.

5. The method according to claim 4, wherein the level of the current during the charging pulses and/or the load pulses is set depending on an internal resistance of the cell and/or a temperature of the cell.

6. The method according to claim 1, wherein a discharging current I_Last is a maximum of 20-25 % of the maximal nominal charging current I_Lmax flows during a load pulse.

7. The method according to claim 1, a level of a discharging current I_Last varies in consecutive load pulses.

8. The method according to claim 1, wherein on exceeding a predetermined voltage of the cell, the charging operation is terminated and/or wherein on exceeding a predetermined temperature (T_max) of the cell the charging operation is terminated.

9. The method according to claim 1, wherein depending on the measured voltage, a level of the charging current I_L is set for the subsequent charging pulse, wherein if the measured voltage U_z of the cell lies above a predefined value during the load pulse, the charging current I_L is reduced in the next charging pulse.

10. The method according to claim 1, wherein depending on the measured voltage, the level of a discharging current I_Last is set for the subsequent load pulse, wherein if the measured voltage U_z of the cell lies above a predefined value during the load pulse, the discharging current I_Last is reduced in the next load pulse.

11. The method according to claim 1, where a length of a load pulse corresponds to about one-half of a length of a charging pulse.

12. The method according to claim 1, wherein if the measured voltage U_z of the cell reaches the end-of-charge voltage U_Lmax during a load pulse, the charging current I_L is reduced in the next charging pulse.

13. A device for charging a lithium-ion based rechargeable cell, comprising a controller configured to:

pulse charge the cell, wherein a charging current I_L, during the charging pulses, exceeds a maximal nominal charging current I_Lmax of the cell by up to 5-times; and

discharge the cell between the charging pulses by load pulses, wherein the load pulses are shorter than the charging pulses, and

finish charging of the cell after a measured voltage UZ at each of a predefined number of load pulses (n) corresponds to an end of-charge voltage U_Lmax of the cell, wherein n is greater than or equal to 1,

wherein a level of the charging current I_L varies in consective charging pulses.

14. The device according to claim 13, further comprising a device for providing a sink in order to discharge the cell during the load pulses, wherein a size of the load pulse can be set.

15. The device according to claim 13, further comprising at least one capacitor to provide the load pulse and/or the charging pulse.