Battery fault detection using temperature measurements in smart home devices

Abstract

A battery pack may use an integrated temperature sensor to monitor a temperature of a battery cell during charging and discharging. However, if the integrated temperature sensor fails, a smart home device may continue to charge and discharge the battery outside of its approved temperature range. This may lead to both safety and performance concerns. To identify a failed integrated temperature sensor, the device may leverage any additional temperature sensors that are located in the device. These temperature sensors may be used to externally measure or estimate the battery temperature. If a sufficient deviation between the measurements of these external temperature sensors and the measurements from the integrated temperature sensor is detected, the device may use the comparison of these temperature measurements to determine that the integrated temperature sensor may be malfunctioning. The device may then change its operational state in response to maintain performance and safety.

What is claimed is: 
     
         1 . A thermostat comprising:
 a battery pack disposed inside of a housing of the thermostat, wherein the battery pack comprises a battery cell and an integrated temperature sensor in the battery pack;   one or more temperature sensors disposed inside of the housing of the thermostat and outside of the battery pack; and   one or more processors that are programmed to perform operations comprising:
 receiving a first temperature measurement from the integrated temperature sensor of the battery pack; 
 receiving a second temperature measurement from the one or more temperature sensors disposed inside the housing of the thermostat and outside of the battery pack; 
 comparing the first temperature measurement with the second temperature measurement; and 
 determining whether the integrated temperature sensor is malfunctioning based at least in part on comparing the first temperature measurement with the second temperature measurement. 
   
     
     
         2 . The thermostat of  claim 1 , wherein the integrated temperature sensor and the battery cell are disposed within a packaging of the battery pack, and the battery pack comprises a wire connector that extends out of the packaging of the battery pack to communicate with the integrated temperature sensor. 
     
     
         3 . The thermostat of  claim 1 , wherein the integrated temperature sensor comprises a Negative Temperature Coefficient (NTC) thermistor for which resistance decreases with increasing temperature. 
     
     
         4 . The thermostat of  claim 1 , wherein the integrated temperature sensor is read by a power management integrated circuit as an analog value and stored in a register of the power management integrated circuit, and the power management integrated circuit provides the value to a processor of the thermostat to determine whether the integrated temperature sensor is malfunctioning. 
     
     
         5 . The thermostat of  claim 1 , wherein the one or more temperature sensors are disposed inside of the housing of the thermostat are mounted to a printed circuit board that is parallel with and proximate to the battery pack. 
     
     
         6 . The thermostat of  claim 5 , wherein the one or more temperature sensors are mounted to the printed circuit board in locations corresponding to different quadrants of the battery pack. 
     
     
         7 . The thermostat of  claim 1 , wherein at least one of the one or more temperature sensors disposed inside the housing of the thermostat are disposed proximate to the integrated temperature sensor of the battery pack. 
     
     
         8 . A method of detecting faulty battery pack temperature sensors, the method comprising:
 receiving a first temperature measurement from an integrated temperature sensor of a battery pack, wherein the battery pack is disposed inside of a housing of a thermostat, and the battery pack comprises a battery cell and the integrated temperature sensor in the battery pack;   receiving a second temperature measurement from one or more temperature sensors disposed inside the housing of the thermostat and outside of the battery pack;   comparing the first temperature measurement with the second temperature measurement; and   determining whether the integrated temperature sensor is malfunctioning based at least in part on comparing the first temperature measurement with the second temperature measurement.   
     
     
         9 . The method of  claim 8 , wherein determining whether the integrated temperature sensor is malfunctioning is based at least in part on determining whether there is more than a threshold difference between the first temperature measurement and the second temperature measurement. 
     
     
         10 . The method of  claim 9 , wherein the threshold difference is calibrated during prior charging and/or discharging cycles of the battery pack. 
     
     
         11 . The method of  claim 8 , further comprising estimating a temperature of the battery pack based on the second temperature measurement from the one or more temperature sensors outside of the battery pack. 
     
     
         12 . The method of  claim 8 , further comprising estimating a temperature of an ambient temperature of an environment outside of the housing of the thermostat using the second temperature measurement from the one or more temperature sensors outside of the battery pack. 
     
     
         13 . The method of  claim 8 , wherein determining whether the integrated temperature sensor is malfunctioning requires at least two consecutive comparisons between temperature measurements from the integrated temperature sensor of the battery pack and the one or more temperature sensors outside of the battery pack. 
     
     
         14 . The method of  claim 8 , further comprising regulating charging of the battery cell based on temperature measurements from the integrated temperature sensor of the battery pack. 
     
     
         15 . A method of compensating for faulty battery pack temperature sensors in smart home devices, the method comprising:
 receiving a first temperature measurement from an integrated temperature sensor of a battery pack of the smart home device;   receiving a second temperature measurement from one or more temperature sensors disposed inside of a housing of a smart home device and outside of the battery pack;   determining that the integrated temperature sensor is malfunctioning based at least in part on the first temperature measurement and the second temperature measurement; and   changing an operational state of the smart home device and/or the battery pack based on determining that the integrated temperature sensor is malfunctioning.   
     
     
         16 . The method of  claim 15 , wherein changing the operational state of the smart home device and/or the battery pack comprises preventing the battery pack from charging after determining that the integrated temperature sensor is malfunctioning. 
     
     
         17 . The method of  claim 15 , wherein changing the operational state of the smart home device and/or the battery pack comprises transitioning the smart home device to a low power or emergency mode. 
     
     
         18 . The method of  claim 15 , wherein changing the operational state of the smart home device and/or the battery pack comprises charging the battery pack during subsequent charging cycles using temperature measurements from the one or more temperature sensors disposed outside of the battery pack instead of the integrated temperature sensor of the battery pack. 
     
     
         19 . The method of  claim 15 , wherein changing the operational state of the smart home device and/or the battery pack comprises causing the smart home device to shut down. 
     
     
         20 . The method of  claim 15 , wherein changing the operational state of the smart home device and/or the battery pack comprises sending an alert to an app on a user device, displaying an alert on a user interface of the smart home device, or sending an alert to a remote server that monitors the smart home device.