Apparatus and method for charging and discharging a battery
View Patent ↗A method and apparatus for controlling the charge and discharge currents in a battery ( 2 ) as a function of temperature. When a battery ( 2 ) is charged or discharged in an environment that approaches its design operating temperature extreme, the currents are reduced to limit self-heating of the battery and thus extend the useful operating environment temperature range. A temperature sensor ( 18 ) is coupled to a controller ( 6 ) to sense the battery ( 2 ) temperature. The temperature information is used to set a suitable charging or discharging current ( 8 ). In the illustrative embodiment, the charging current is set to a maximum value when said temperature is lower than a first predetermined threshold value, the maximum value being the battery's maximum specified charging current, and the first predetermined threshold value being the battery's maximum charging temperature.
1. An apparatus for exercising a battery, comprising
a charging circuit having a charging current output coupled to the battery;
a temperature sensor positioned to sense a temperature related to the battery temperature;
a discharging circuit having a variable impedance load and a discharging current input coupled to the battery;
a controller coupled to said temperature sensor, said charging circuit, and said discharging circuit, said controller operable to set said charging current in accordance with said temperature, and operable to set said discharging current in accordance with said temperature, said controller being operable to minimize said charging current when said temperature is higher than a first predetermined threshold value; and
a memory coupled to said controller having a look up table with temperature versus discharging current and values of said variable impedance load stored therein, whereby said controller accesses said look up table to set said discharging current.
2. The apparatus of claim 1 and wherein said controller continuously sets said discharging current in accordance with said temperature.
3. The apparatus of claim 1 and wherein said controller periodically sets said discharging current in accordance with said temperature.
4. The apparatus of claim 1 and wherein said controller is operable to set said discharging current to a maximum value when said temperature is lower than a second predetermined threshold value.
5. The apparatus of claim 1 wherein said maximum value is the battery's maximum specified discharging current and said first predetermined threshold value is the battery's maximum discharging temperature.
6. The apparatus of claim 1 wherein said temperature sensor senses the temperature of the battery and said discharging circuit.
7. A method of exercising a battery, comprising the steps of:
sensing a temperature related to the battery temperature;
setting a discharging current in accordance with said temperature by recalling a discharging current corresponding to said sensed temperature from a look up table;
discharging the battery at said discharging current with a discharging circuit having a variable impedance load, the impedance of said load being selected from said look up table;
discontinuing said discharging step when a predetermined battery voltage is reached;
setting a charging current in accordance with said temperature, said setting step further including the step of minimizing said charging current when said temperature is higher than a first predetermined threshold value; and
charging the battery at said charging current.
8. The method of claim 7 and wherein said sensing and setting a discharge current steps are repeated continuously during said discharging step.
9. The method of claim 7 and wherein said sensing and setting a discharge current steps are repeated periodically during said discharging step.
10. The method of claim 7 and wherein said setting step includes setting said discharging current to a maximum value if said temperature is lower than a second predetermined threshold.
11. The method of claim 10 and wherein said maximum value is the battery's maximum specified discharging current, and said first predetermined threshold is the battery's maximum discharging temperature.
12. The method of claim 7 wherein the battery is coupled to a load, and wherein said sensing step includes the step of sensing the temperature of the battery and the load.