Temperature dependent charge algorithm

• US 10,547,189 B2
• Filed: 04/27/2016
• Issued: 01/28/2020
• Est. Priority Date: 04/29/2015
• Status: Active Grant

• Current Assignee: RIOT Energy Incorporated
• Original Assignee: ZPower, LLC
• Inventors: Pourdarvish, Reza, Powers, Timothy W., Renken, Troy W.
• Primary Examiner(s): Siek, Vuthe
• Application Number:
  US15/566,764
• Publication Number:
  US 20180123369A1
• Time in Patent Office: 1,371 Days
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
• CPC Class Codes: H02J 7/00041 in response to measured battery parameters, e.g. voltage, current or temperature profile
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence
• CPC Class Codes: H02J 7/007 Regulation of charging or discharging current or voltage
• CPC Class Codes: H02J 7/007182 in response to battery voltage
• CPC Class Codes: H02J 7/007192 in response to temperature

Abstract

A method (600, 700, 800) for charging a battery (102) comprises obtaining, by charging circuitry (120), an open circuitry voltage of the battery prior to a charging session. The charging circuitry is in electrical communication with a power source (110) and the battery. The method also comprises initiating the charging session to charge the battery at a constant charge current-constant charge voltage with power provided from the power source and obtaining an ambient temperature (T) measured by a temperature sensor (160) in communication with the charging circuitry. The method also comprises obtaining a charge termination time (t_t) based on the ambient temperature and terminating the charging session when the charge termination time is reached.

Claims

1. A method for charging a rechargeable battery comprising:

obtaining, by charging circuitry, an open circuit voltage of the battery prior to a charging session, the charging circuitry in electrical communication with a power source and the battery;

initiating, by the charging circuitry, the charging session to charge the battery at a constant charge current-constant charge voltage with power provided from the power source, the charging session corresponding to one of a first charging strategy or a second charging strategy based on the obtained open circuit voltage of the battery;

obtaining, by the charging circuitry, an ambient temperature (T) measured by a temperature sensor in communication with the charging circuitry;

obtaining, by the charging circuitry, a charge termination time (t_t) based on the ambient temperature (T); and

terminating, by the charging circuitry, the charging session when the charge termination time (t_t) is reached; and

when the charging session corresponds to the first charging strategy;

initiating, by the charging circuitry, a timer (t) when the charging session to charge the battery at the constant charge current-constant charge voltage initiates; and

when a voltage (V_bat) of the battery reaches a predetermined voltage after initiating the charging session;

obtaining, by the charging circuitry, the ambient temperature (T) and a polarization time (t_p), the polarization time (t_p) corresponding to a value of the timer (t) from when the charging session initiates until the battery voltage (V_bat) reaches the predetermined voltage; and

estimating, by the charging circuitry, the charge termination time (t_t) as a function of the ambient temperature (T), the polarization time (t_p), the charge current, and the charge voltage.

2. The method of claim 1, wherein the charging session corresponds to the first charging strategy when the obtained battery open circuit voltage is less than a voltage threshold and the charging session corresponds to the second charging strategy when the obtained battery open circuit voltage is greater than the voltage threshold.

3. The method of claim 1, further comprising terminating, by the charging circuitry, the charging session if the battery voltage (V_bat) does not reach the predetermined voltage within a polarization time threshold and the battery voltage (V_bat) is less than a termination voltage threshold.

4. The method of claim 1, wherein the predetermined voltage corresponds to one of a peak polarization voltage (V_PP) or a predetermined voltage value near the peak polarization voltage (V_PP).

5. The method of claim 1, further comprising, after the voltage (V_bat) of the battery reaches the predetermined voltage:

continuing to charge the battery at the constant charge current-constant charge voltage until the battery voltage (V_bat) reaches a voltage limit, the voltage limit corresponding to a maximum battery voltage (V_{bat_max});

decreasing, by the charging circuitry, the charge current at a rate when the battery voltage (V_bat) reaches the voltage limit; and

terminating the charging session upon the earlier one of the timer (t) reaching the charge termination time (t_t) or the charge current falling below a charge current threshold.

6. The method of claim 1, wherein obtaining the charge termination time (t_t) when the charging session corresponds to the second charging strategy comprises:

initiating, by the charging circuitry, a timer (t) when the charging session initiates;

obtaining the ambient temperature (T) when the timer (t) reaches an initial charging time; and

estimating, by the charging circuitry, the charge termination time (t_t) and an end of charge current as a function of the ambient temperature (T), the charge current, and the charge voltage.

7. The method of claim 6, further comprising, after the timer (t) reaches the initial charging time:

continuing to charge the battery at the constant charge current-constant charge voltage until the battery voltage (V_bat) reaches a voltage limit, the voltage limit corresponding to a maximum battery voltage (V_{bat_max});

decreasing, by the charging circuitry, the charge current at a rate when the battery voltage (V_bat) reaches the voltage limit; and

terminating the charging session upon the earlier one of the timer (t) reaching the charge termination time (t_t) or the charge current falling below the end of charge current for a current termination period.

8. The method of claim 6, further comprising, after the timer (t) and the charging session initiate, terminating, by the charging circuitry, the charging session if the charge current falls below a charge current threshold within the initial charging time.

9. The method of claim 1, wherein the battery comprises a silver-zinc battery type.

10. The method of claim 1, wherein the battery comprises a single cell or two or more cells in series, and wherein the charging circuitry is implemented upon a silicon chip.

11. An apparatus for charging a rechargeable battery comprising:

a temperature sensor configured to measure ambient temperature (T); and

charging circuitry in electrical communication with the temperature sensor, the battery, and a power source, the charging circuitry configured to;

initiate a charging session to charge the battery at a constant charge current to a maximum battery voltage (V_{bat_max}) with power provided from the power source;

obtain the ambient temperature (T) from the temperature sensor;

obtain a charge termination time (t_t) based on the ambient temperature (T); and

terminate the charging session when the charge termination time (t_t) is reached; and

wherein, according to a first charging strategy, the charging circuitry is further configured to;

obtain an open circuit voltage of the battery prior to initiating the charging session;

determine the battery is indicative of being in a lower voltage plateau prior to initiating the charging session when the battery open circuit voltage is less than a voltage threshold;

obtain the ambient temperature (T) and a polarization time (t_p) when a voltage (V_bat) of the battery under load reaches a predetermined voltage after initiating the charging session, the polarization time (t_p) corresponding to a time from when the charging session initiates until the battery voltage (V_bat) reaches the predetermined voltage; and

estimate the charge termination time (t_t) as a function of the ambient temperature (T) and the polarization time (t_p).

12. The apparatus of claim 11, wherein the charging circuitry is further configured to:

after the battery voltage (V_bat) reaches the predetermined voltage, continue charging the battery at the constant charge current until the battery voltage (V_bat) reaches the maximum battery voltage (V_{bat_max});

decrease the charge current at a rate when the battery voltage (V_bat) reaches the maximum battery voltage (V_{bat_max}); and

terminate the charging session upon the earlier one of the charge termination time (t_t) or the charge current falling below a charge current threshold.

13. The apparatus of claim 11, wherein the predetermined voltage corresponds to one of a peak polarization voltage (V_PP) or a predetermined voltage value near the peak polarization voltage (V_PP).

14. The apparatus of claim 11, wherein, according to a second charging strategy, the charging circuitry is further configured to:

obtain an open circuit voltage of the battery prior to initiating the charging session;

determine the battery is indicative of being in an upper voltage plateau prior (210) to initiating the charging session when the battery open circuit voltage is greater than a voltage threshold;

initiate a timer (t) when the charging session initiates;

obtain the ambient temperature (T) when the timer (t) reaches an initial charging time; and

estimate the charge termination time (t_t) and an end of charge current as a function of the ambient temperature (T).

15. The apparatus of claim 14, wherein the charging circuitry is further configured to:

after the timer (t) reaches the initial charging time, continue charging the battery at the constant charge current until the battery voltage (V_bat) reaches the maximum battery voltage (V_{bat_max});

decrease the charge current at a rate when the battery voltage (V_bat) reaches the maximum battery voltage (V_{bat_max}); and

terminate the charging session upon the earlier one of the timer (t) reaching the charge termination time (t_t) or the charge current falling below the end of charge current for a current termination period.

16. The apparatus of claim 14, wherein the charging circuitry is further configured to terminate the charging session if the charge current falls below a charge current threshold within the initial charging time.

17. The apparatus of claim 11, wherein the battery comprises a single cell or two or more cells in series having a silver-zinc battery type.

18. The apparatus of claim 11, further comprising a silicon chip implementing the charging circuitry and the temperature sensor.

19. The apparatus of claim 18, wherein the silicon chip is located in a device powered by the battery.

20. The apparatus of claim 18, wherein the silicon chip is located in a charging base, the charging base configured to electrically connect to the battery and the power source.

21. A charging system comprising:

a rechargeable battery configured to provide power to electrical components of a device;

a power source; and

a charger comprising charging circuitry in electrical communication with the power source and the battery when the battery is docked with the charging circuitry, the charging circuitry;

obtaining an open circuit voltage of the battery prior to a charging session when the battery is docked with the charging circuitry;

initiating the charging session to charge the battery at a constant charge current to a maximum battery voltage (V_{bat_max}) with power provided from the power source, the charging session corresponding to one of a first charging strategy or a second charging strategy based on the obtained battery open circuit voltage;

obtaining an ambient temperature (T) measured by a temperature sensor in communication with the charging circuitry;

obtaining a charge termination time (t_t) based on the ambient temperature (T); and

terminating the charging session when the charge termination time (t_t) is reached; and

wherein the charging circuitry obtains the charge termination time (t_t) according to the first charging strategy by;

determining the battery is indicative of being in a lower voltage plateau prior to initiating the charging session when the battery open circuit voltage is less than a voltage threshold;

obtaining the ambient temperature (T) and a polarization time (t_p) when a voltage (V_bat) of the battery under load reaches a predetermined voltage after initiating the charging session, the polarization time (t_p) corresponding to a time from when the charging session initiates until the battery voltage (V_bat) reaches the predetermined voltage; and

estimating the charge termination time (t_t) as a function of the ambient temperature (T) and the polarization time (t_p).

22. The system of claim 21, wherein the charging circuitry terminates the charging session by:

after the battery voltage (V_bat) reaches the predetermined voltage, continuing to charge the battery at the constant charge current until the battery voltage (V_bat) reaches the maximum battery voltage (V_{bat_max});

decreasing the charge current at a rate when the battery voltage (V_bat) reaches the maximum battery voltage (V_{bat_max}); and

terminating the charging session upon the earlier one of the charge termination time (t_t) or the charge current falling below a charge current threshold.

23. The system of claim 21, wherein the charging circuitry obtains the charge termination time (t_t) according to the second charging strategy by:

determining the battery is indicative of being in an upper voltage plateau prior to initiating the charging session when the battery open circuit voltage is greater than a voltage threshold;

initiating a timer (t) when the charging session initiates;

obtaining the ambient temperature (T) when the timer (t) reaches an initial charging time; and

estimating the charge termination time (t_t) and an end of charge current as a function of the ambient temperature (T).

24. The system of claim 23, wherein the charging circuitry terminates the charging session by:

after the timer (t) reaches the initial charging time, continuing to charge the battery at the constant charge current until the battery voltage (V_bat) reaches the maximum battery voltage (V_{bat_max});

decreasing the charge current at a rate when the battery voltage (V_bat) reaches the maximum battery voltage (V_{bat_max}); and

terminating the charging session upon the earlier one of the timer (t) reaching the charge termination time (t_t) or the charge current falling below the end of charge current for a current termination period.

25. The system of claim 21, wherein the battery comprises a silver-zinc battery type and the battery-powered device comprises a hearing aid device.

26. The system of claim 21, wherein the charging circuitry is located within the battery-powered device or a charging base external to the battery-powered device.