Method and apparatus for reducing battery charge time and energy consumption, as in a nickel metal hydride battery pack
First Claim
1. In a rechargeable electrochemical battery system having a series arrangement of multiple batteries in a pack, and a pack cooling system having a cooling mode, a method of optimizing the charging of the battery pack, comprising the steps of:
- establishing pre-selected charge efficiency values as a function of battery pack temperature and state of charge (SOC), including a threshold value CE below which charging is considered to be not optimal;
establishing a pre-selected pack temperature criterion (Thi) above which pack cooling by the pack cooling system is considered reduced in effectiveness;
measuring overall pack temperature;
performing a full charging event if the measured pack temperature is below Thi or if the thermal system is not in a cooling mode;
if the pack temperature is above Thi, measuring SOC of the battery pack;
(i) then determining the then-existing charge efficiency (CEt);
(ii) comparing CEt against the threshold value CE;
completing any charge cycle underway if CEt is below the threshold value CE, and then proceeding to a support mode without equalization;
if CEt is above the threshold value CE, continuing charging with periodic repetition of steps (i) and (ii) until full charging is completed or until CEt falls below the threshold value CE, in which event any charge cycle underway is completed and the support mode is entered.
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Abstract
The present invention in one form provides for an improved battery charging apparatus and method comprising a controller and battery balancing system including an algorithm which monitors temperature of the battery pack and state of charge. These are factored for a charge efficiency through comparison to a pre-determined table of charge efficiency values, and then compared against a threshold charge efficiency below which charging is considered not optimal. The charging operation is discontinued in the event charge efficiency is below the threshold value.
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Citations
11 Claims
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1. In a rechargeable electrochemical battery system having a series arrangement of multiple batteries in a pack, and a pack cooling system having a cooling mode, a method of optimizing the charging of the battery pack, comprising the steps of:
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establishing pre-selected charge efficiency values as a function of battery pack temperature and state of charge (SOC), including a threshold value CE below which charging is considered to be not optimal;
establishing a pre-selected pack temperature criterion (Thi) above which pack cooling by the pack cooling system is considered reduced in effectiveness;
measuring overall pack temperature;
performing a full charging event if the measured pack temperature is below Thi or if the thermal system is not in a cooling mode;
if the pack temperature is above Thi, measuring SOC of the battery pack;
(i) then determining the then-existing charge efficiency (CEt);
(ii) comparing CEt against the threshold value CE;
completing any charge cycle underway if CEt is below the threshold value CE, and then proceeding to a support mode without equalization;
if CEt is above the threshold value CE, continuing charging with periodic repetition of steps (i) and (ii) until full charging is completed or until CEt falls below the threshold value CE, in which event any charge cycle underway is completed and the support mode is entered. - View Dependent Claims (2, 3, 4)
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5. In a rechargeable electrochemical battery system having a series arrangement of multiple batteries in a pack, and a pack cooling system having a cooling mode, a method of optimizing the charging of the battery pack, comprising the steps of:
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establishing pre-selected charge efficiency values as a function of battery pack temperature and state of charge (SOC), including a threshold value CE below which charging is considered to be not optimal;
establishing a pre-selected pack temperature criterion (Thi) above which pack cooling by the pack cooling system is considered reduced in effectiveness;
establishing a threshold SOCCE below which CE is not considered as a charge completion criterion;
measuring overall pack temperature;
performing a full charging event if the measured pack temperature is below Thi or if the thermal system is not in a cooling mode;
if the pack temperature is above Thi, measuring SOC of the battery pack;
(i) then determining the then-existing charge efficiency (CEt);
(ii) comparing SOC against SOCCE;
(iii) comparing CEt against the threshold value CE;
completing any charge cycle underway if CEt is below the threshold value CE, and SOC is greater than SOCCE, and then proceeding to a support mode without equalization;
if CEt is above the threshold value CE or SOC is less than SOCCE, continuing charging with periodic repetition of steps (i), (ii) and (iii) until full charging is completed or until CEt falls below the threshold value CE and SOC is greater than SOCCE, in which event any charge cycle underway is completed and the support mode is entered.
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6. An apparatus for improved battery charging in a rechargeable electrochemical battery system having a series arrangement of multiple batteries in a pack, and a pack cooling system having a cooling mode, comprising:
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a battery pack controller having comparator circuitry, said controller being programmed with pre-selected charge efficiency data values as a function of battery pack temperature and state of charge (SOC), including a threshold value CE below which charging is considered to be not optimal, and being programmed with a pre-selected cooling medium temperature criterion (Thi) above which cooling by the pack cooling system is considered reduced in effectiveness;
a temperature sensor communicating with a pack temperature sensing point, said temperature sensor generating a temperature signal;
a current sensor communicating with the battery pack and measuring a current which is used to calculate state of charge, said current sensor generating a current signal;
signal circuitry communicating said temperature signal and said current signal to said controller;
charge circuitry connecting a source of current to each said battery; and
said controller having a charging program for optimum charging which measures overall pack temperature and cooling medium temperature, and performs a full charging event if the measured cooling medium temperature is below Thi or if the thermal system is not in a cooling mode, and if the cooling medium temperature is above Thi, measuring SOC of the battery pack, (i) then determining the then-existing charge efficiency (CEt), (ii) comparing CEt against the threshold value CE, and completing any charge cycle underway if CEt is below the threshold value CE, thereafter proceeding to a support mode without equalization, and if CEt is above the threshold value CE, continuing charging including equalization with periodic repetition of steps (i) and (ii) until full charging is completed or until CEt falls below the threshold value CE, in which event any charge cycle underway is completed and the support mode is entered. - View Dependent Claims (7, 8)
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9. An apparatus for improved battery charging in a rechargeable electrochemical battery system having a series arrangement of multiple batteries in a pack, and a pack cooling system having a cooling mode, comprising:
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battery pack controller means having comparator circuitry, said controller means being programmed with pre-selected charge efficiency data values as a function of battery pack temperature and state of charge (SOC), including a threshold value CE below which charging is considered to be not optimal, and being programmed with a pre-selected cooling medium inlet temperature criterion (Thi) above which pack cooling by the pack cooling system is considered reduced in effectiveness;
a temperature sensing means communicating with a pack temperature sensing point, said temperature sensing means generating a temperature signal;
a current sensing means communicating with the battery pack for calculation of SOC and generating a current signal;
signal circuitry means communicating said temperature signal and said current signal to said controller means;
charge circuitry means for connecting a source of current to each said battery; and
said controller means having a charging program means for optimum charging which measures overall pack temperature and cooling medium temperature, and performs a full charging event if the measured cooling medium temperature is below Thi or if the thermal system is not in a cooling mode, and if the cooling medium temperature is above Thi, measuring SOC of the battery pack, (i) then determining the then-existing charge efficiency (CEt), (ii) comparing CEt against the threshold value CE, and completing any charge cycle underway if CEt is below the threshold value CE, thereafter proceeding to a support mode without equalization, and if CEt is above the threshold value CE, continuing any charge cycle including equalization with periodic repetition of steps (i) and (ii) until full charging is completed or until CEt falls below the threshold value CE, in which event charging is terminated and the support mode is entered. - View Dependent Claims (10, 11)
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Specification