Method for charging a battery using a thermal model for an electrical device connected to the battery

A system for charging a battery, comprising:

• an electrical device coupled in a circuit between the battery and an electrical power source, the electrical device having an on state configured to connect the power source to the battery and an off state configured to disconnect the power source from the battery, the on and off states being mechanically different states of the electrical device;
• one or more computer processors;
• one or more non-transitory computer-readable storage media;
• and
• program instructions, stored on the one or more non-transitory computer-readable storage media, which when implemented by the one or more processors, cause the one or more computer processors to perform the steps of:
• charging the battery by setting the electrical device to the on state;
• measuring current flowing through contacts of the electrical device while the electrical device is in the on state;
• determining current as a function of time flowing through the contacts of the electrical device;
• using the current as a function of time as a variable in a thermal model based on heating of the contacts and cooling of the contacts;
• determining by the thermal model a predicted temperature of the contacts based on the current as a function of time and the heating and cooling of the contacts;
• and
• controlling the on and off state of the electrical device based on the predicted temperature.

A system for predicting temperature as a function of time of an electrical device coupled in a circuit between a battery and an electrical power source, the electrical device having an on state configured to connect the power source to the battery and an off state configured to disconnect the power source from the battery, the on and off states being mechanically different states of the electrical device, the system comprising:

• one or more computer processors;
• one or more non-transitory computer-readable storage media;
• and
• program instructions, stored on the one or more non-transitory computer-readable storage media, which when implemented by the one or more processors, cause the one or more computer processors to perform the steps of:
• generating an on/off cycle temperature curve of temperature versus time based on on/off cycle temperature measurements obtained by measuring the temperature of the electrical device during the on/off cycle by running a test current through the electrical device for a specified time period while the electrical device is in the on state and turning off the test current for a second specified time period while the electrical device is in the off state;
• extracting a heating curve from the on/off cycle temperature curve, the heating curve representing both heating and cooling of the electrical device during the on cycle;
• extracting a cooling curve from the on/off cycle temperature curve, the cooling curve representing cooling of the electrical device during the off cycle;
• calculating a heating change in temperature as a function of temperature curve based on the extracted heating curve;
• calculating a cooling change in temperature as a function of temperature curve based on the extracted cooling curve;
• generating an on/off cycle heating behavior curve by combining the heating temperature change curve and the cooling temperature change curve;
• and
• generating the thermal model for the electrical device based on the on/off cycle heating behavior curve and the calculated heating change in temperature as a function of temperature and the calculated cooling change in temperature as a function of temperature.