Method for operating a battery charger, and a battery charger

• US 10,328,807 B2
• Filed: 03/16/2016
• Issued: 06/25/2019
• Est. Priority Date: 03/16/2015
• Status: Active Grant

• Current Assignee: CTEK Sweden AB (CTEK Holding AB)
• Original Assignee: CTEK Sweden AB (CTEK Holding AB)
• Inventors: Eriksson, Per, Eriksson, Linus, Frojd, Hans-Olof
• Primary Examiner(s): Fantu, Yalkew
• Application Number:
  US15/557,524
• Publication Number:
  US 20180050598A1
• Time in Patent Office: 1,196 Days
• Field of Search: 320109
• CPC Class Codes: B60L 53/14 Conductive energy transfer
• CPC Class Codes: B60L 53/22 Constructional details or arrangements of charging converters specially adapted for charging electric vehicles
• CPC Class Codes: B60L 58/12 responding to state of charge [SoC]
• CPC Class Codes: G01R 31/36 Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
• CPC Class Codes: G01R 31/386 using test-loads
• CPC Class Codes: G01R 31/388 involving voltage measurements
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H02J 2310/48 for electric vehicles [EV] or hybrid vehicles [HEV]
• CPC Class Codes: H02J 7/00041 in response to measured battery parameters, e.g. voltage, current or temperature profile
• CPC Class Codes: H02J 7/00047 with provisions for charging different types of batteries
• CPC Class Codes: H02J 7/00304 Overcurrent protection
• CPC Class Codes: H02J 7/00309 Overheat or overtemperature protection
• CPC Class Codes: H02J 7/0049 Detection of fully charged condition
• CPC Class Codes: H02J 7/00711 with introduction of pulses during the charging process
• CPC Class Codes: H02J 7/00718 in response to charge current gradient
• CPC Class Codes: H02J 7/007184 in response to battery voltage gradient
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 90/12 : Electric charging stations
• CPC Class Codes: Y02T 90/14 : Plug-in electric vehicles

Abstract

The present invention relates to a method for operating a battery charger, and a battery charger. The method comprising the steps of determining a capacity of the battery, determining an initial charging current, apply the calculated initial charging current as a charging current to the battery, determining the voltage change with time ΔV/Δt for the voltage over the battery, adjusting the charging current based on the ΔV/Δt.

Claims

1. A method for operating a battery charger configured to be connected to a battery, comprising the steps of:

connecting the battery to the battery charger;

determining a capacity (C) of the battery, wherein the step of determining the capacity (C) of the battery comprises applying an electrical pulse to the connected battery, calculating a conductivity (G) of the battery using a voltage difference (Δ

V₁₂) between a first voltage (V1) and a second voltage (V2) measured during and after said pulse and calculating the capacity (C) using a capacity function that determines the capacity (C) of the battery for the given conductivity (G);

determining an initial charging current using the capacity (C) of the battery;

applying the determined initial charging current as a charging current to the battery;

determining the voltage change with time Δ

V/Δ

t over the battery;

adjusting the charging current based on the voltage change with time Δ

V/Δ

t to obtain a predetermined rate of change of the output voltage Δ

V/Δ

t.

2. The method according to claim 1, wherein the step of determining the capacity (C) of the battery further comprises:

generating the electrical pulse across a plus pole and a minus pole of the battery;

measuring the first voltage (V1) across the plus pole and the minus pole at a first time during said pulse;

measuring the second voltage (V2) across the plus pole and the minus pole at a second time after said pulse;

calculating the voltage difference (Δ

V₁₂) between said first voltage and said second voltage;

calculating the conductivity (G) of the battery according to;

G=I_pulse/Δ

V₁₂ where I_pulse is the current of the electrical pulse;

calculating the capacity (C) of the battery according to;

C=q(G), where q(G) is a capacity function that gives the capacity (C) of the battery for a given conductivity (G).

3. The method according to claim 2, wherein the electrical pulse is a constant current pulse.

4. The method according to claim 3, wherein the constant current pulse has a predetermined duration.

5. The method according to claim 4, wherein the constant current pulse has a predetermined duration larger than 15 seconds.

6. The method according to claim 5, wherein the constant current pulse has a predetermined duration in an interval from 15 seconds up to 30 seconds.

7. The method according to claim 2, wherein the first time is at an end of the electrical pulse.

8. The method according to claim 2, wherein the second time is at a predetermined time length from said first time.

9. The method according to claim 2, wherein the capacity function is a linear function of the conductivity q(G)=k×

G, where k is a battery constant.

10. The method according to claim 9, wherein the battery constant k depends on the battery chemistry of the battery.

11. The method according to claim 2, wherein the capacity function comprises a linear function of the conductivity.

12. The method according to claim 2, further comprising:

determining the voltage of the battery;

if it is determined that the voltage of the battery is equal to a voltage indicative of a fully charged battery, exit the method.

13. A battery charger comprising:

a voltage converter configured to convert an input voltage to an output voltage, the voltage converter is further connected to an output means configured to be connected to a battery;

a processor and a memory, wherein the memory comprises instructions for executing the method according to claim 2 when the battery charger is connected to the battery, and the processor is configured to execute said instructions, and wherein the processor further comprises means for controlling the voltage converter, and means for detecting the output voltage and the output current of the output means.

14. The method according to claim 1, wherein the step of adjusting the charging current involves using a proportional controller.

15. The method according to claim 14, wherein the predetermined rate of change is in the interval from 1 mV/min to 100 mV/min.

16. The method according to claim 14, wherein the predetermined rate of change is in the interval from 5 mV/min to 50 mV/min.

17. The method according to claim 1, wherein the step of adjusting the charging current, comprises:

if it is determined that the voltage change with time Δ

V/Δ

t is smaller than a predetermined rate of change, increasing the charging current;

if it is determined that the voltage change with time Δ

V/Δ

t is larger than the predetermined rate of change, decreasing the charging current.

18. A battery charger comprising:

a voltage converter configured to convert an input voltage to an output voltage, the voltage converter is further connected to an output means configured to be connected to a battery;

a processor and a memory, wherein the memory comprises instructions for executing the method according to claim 17 when the battery charger is connected to the battery, and the processor is configured to execute said instructions, and wherein the processor further comprises means for controlling the voltage converter, and means for detecting the output voltage and the output current of the output means.

19. The method according to claim 1, further comprising:

determining the voltage of the battery;

if it is determined that the voltage of the battery is equal to a voltage indicative of a fully charged battery, exit the method.

20. A battery charger comprising:

a voltage converter configured to convert an input voltage to an output voltage, the voltage converter is further connected to an output means configured to be connected to a battery;

a processor and a memory, wherein the memory comprises instructions for executing the method according to claim 1 when the battery charger is connected to the battery, and the processor is configured to execute said instructions, and wherein the processor further comprises means for controlling the voltage converter, and means for detecting the output voltage and the output current of the output means.