Fast charging with negative ramped current profile

• US 8,643,342 B2
• Filed: 12/31/2009
• Issued: 02/04/2014
• Est. Priority Date: 12/31/2009
• Status: Active Grant

• Current Assignee: Tesla Inc.
• Original Assignee: Tesla Motors Incorporated (Tesla Inc.)
• Inventors: Mehta, Vineet Haresh, Straubel, Jeffrey Brian
• Primary Examiner(s): DIAO, M BAYE
• Application Number:
  US12/651,246
• Publication Number:
  US 20110156661A1
• Time in Patent Office: 1,496 Days
• Field of Search: 320/156, 320/157, 320/160, 320162-164
• US Class Current: 320/160
• CPC Class Codes: H02J 7/0071 with a programmable schedule

Abstract

A battery cell charging system, including a charger and a controller, for rapidly charging a lithium ion battery cell, the battery cell charging system having a circuit for charging the battery cell using an adjustable voltage charging-profile to apply a charging voltage and a charging current to the battery cell wherein the adjustable voltage charging-profile includes: a first charging stage with a constant first stage charging current and an increasing battery cell voltage with the first stage charging current provided until the first stage charging voltage is about equal to a first stage complete voltage less than a maximum battery cell voltage; an intermediate ramped charging stage, the intermediate ramped charging stage including both an increasing ramped voltage and a decreasing ramped iBat current for the battery cell for the voltage charging range of the first stage complete voltage to about the maximum battery cell voltage; and a final charging stage with a constant final stage charging voltage about equal to the maximum battery cell voltage and a decreasing final stage charging current with the final stage charging voltage provided until the final stage charging current reaches a desired charge complete level.

Claims

1. A battery cell charging system, including a charger and a controller, for charging a lithium ion battery cell, the battery cell charging system comprising:

a circuit for charging the battery cell using an adjustable voltage charging-profile to apply a charging voltage and a charging current to the battery cell wherein said adjustable voltage charging-profile includes;

a first charging stage with a constant first stage charging current and an increasing battery cell voltage with said first stage charging current provided until said first stage charging voltage is about equal to a first stage complete voltage less than a maximum battery cell voltage;

a second ramped charging stage, said second ramped charging stage including both an increasing ramped voltage and a decreasing ramped iBat current for the battery cell for the voltage charging range of said first stage complete voltage to about said maximum battery cell voltage, the ramped iBat current starting to decrease at the constant first stage charging current, wherein said second ramped charging stage has a slope responsive to an imaginary resistance R_Bad established for the battery cell; and

a third charging stage with a constant third stage charging voltage about equal to said maximum battery cell voltage and a decreasing third stage charging current with said third stage charging voltage provided until said third stage charging current reaches a desired charge complete level.

2. The battery cell charging system of claim 1 wherein said second ramped charging stage includes a plurality of uniform stepwise voltage and current changes.

3. The battery cell charging system of claim 1 wherein said first stage charging current has a magnitude about equal to a number X times C and said decreasing ramped i_Bat current has a magnitude about equal to 0.3 times said magnitude of said first stage charging current.

4. The battery cell charging system of claim 3 wherein said decreasing ramped i_Bat current is a function of a final CC current (CC_Final), an initial CC current (CC_Init), a temperature limit of the battery cell, an impedance of the battery cell, and a rate of temperature change of the battery cell.

5. The battery cell charging system of claim 4 wherein said first charging stage ends at time t₁, wherein said third charging stage has a target time to begin at time t₄, and wherein said rate of temperature change produces a function Y(t) dependent upon t₄−

t₁, said decreasing ramped i_Bat current is directly related to;

6. The battery cell charging system of claim 5 wherein said function Y(t) is included in a range from about ½

(t₂+t₃) to about ⅚

(t₂+t₃) wherein t₄−

t₁ is less than t₂+t₃, wherein t₂ and t₃ are periods from a non-ramped four-stage charging profile for the battery cell, said four-stage charging profile having a CC first stage, a CV second stage, a CC third stage and a CV fourth stage, and wherein t₂ is a duration of said CV second stage and t₃ is a duration of said CC third stage.

7. A battery cell charging method for rapidly charging a lithium ion battery cell, the battery cell charging method comprising:

(a) applying, to the battery cell, a constant first stage charging current and an increasing battery cell voltage with said first stage charging current provided until said first stage charging voltage is about equal to a first stage complete voltage less than a maximum battery cell voltage; and

thereafter

(b) applying, to the battery cell, a second ramped charging stage, said intermediate ramped charging stage including both an increasing ramped voltage and a decreasing ramped iBat current for the battery cell for the voltage charging range of said first stage complete voltage to about said

maximum battery cell voltage, the ramped iBat current starting to decrease at the constant first stage charging current, wherein said second ramped charging stage has a sloe responsive to an imaginary resistance R_Bad established for the batter cell; and

thereafter

(c) applying, to the battery cell, a constant third stage charging voltage about equal to maximum battery cell voltage and a decreasing third stage charging current with said third stage charging voltage provided until said third stage charging current reaches a desired charge complete level.

8. The battery cell charging method of claim 7 wherein said second ramped charging stage includes a plurality of uniform stepwise voltage and current changes.

9. The battery cell charging method of claim 7 wherein said first stage charging current has a magnitude about equal to a number X times C and said decreasing ramped i_Bat current has a magnitude about equal to 0.3 times said magnitude of said first stage charging current.

10. The battery cell charging method of claim 9 wherein said decreasing ramped i_Bat current is a function of a final CC current (CC_Final), an initial CC current (CC_Init), a temperature limit of the battery cell, an impedance of the battery cell, and a rate of temperature change of the battery cell.

11. The battery cell charging method of claim 10 wherein said first charging stage ends at time t₁, wherein said third charging stage has a target time to begin at time t₄, and wherein said rate of temperature change produces a function Y(t) dependent upon t₄−

t₁, said decreasing ramped i_Bat current is directly related to;

12. The battery cell charging method of claim 11 wherein said function Y(t) is included in a range from about ½

(t₂+t₃) to about ⅚

(t₂+t₃) wherein t₄−

t₁ is less than t₂+t₃, wherein t₂ and t₃ are periods from a non-ramped four-stage charging profile for the battery cell, said four-stage charging profile having a CC first stage, a CV second stage, a CC third stage and a CV fourth stage, and wherein t₂ is a duration of said CV second stage and t₃ is a duration of said CC third stage.

13. A battery cell charging system, including a charger and a controller, for charging a lithium ion battery cell, the battery cell charging system comprising:

a circuit for charging the battery cell using an adjustable voltage charging-profile to apply a charging voltage and a charging current to the battery cell wherein said adjustable voltage charging-profile includes;

a first charging stage with a constant first stage charging current and an increasing battery cell voltage with said first stage charging current provided until said first stage charging voltage is about equal to a first stage complete voltage less than a maximum battery cell voltage;

a second charging stage, said second charging stage providing a substantially constant power profile for the battery cell for the voltage charging range of said first stage complete voltage to about said maximum battery cell voltage, wherein a ramped iBat current starts to decrease at the constant first stage charging current and has a slope responsive to an imaginary resistance R_Bad established for the batter cell; and

a third charging stage with a constant third stage charging voltage about equal to said maximum battery cell voltage and a decreasing third stage charging current with said third stage charging voltage provided until said third stage charging current reaches a desired charge complete level.