I'm making a battery protection board for a 3S1P pack. I wanted to include two thermistors in the pack to monitor the cell temperature because of how I want to position the batteries. The batteries are going to aligned in a straight row, so I wanted a thermistor in between battery 1 and 2, and another one in between battery 2 and 3. My issue is that the battery protection IC that I'm using (BQ77915) only has one channel for a battery thermistor. I wanted to know if there was anything that I could do to have the protection IC only see the temperature of the hottest battery.
You could feed each Thermistor output into an input of an Analog 2:1 Multiplexer, and also into a Comparator. Then use the comparator output as the Select signal for the Analog 2:1 Multiplexer. Which thermistor goes into the positive terminal of the Comparator and which goes into the negative intput of the Comparator depends on whether the thermistors are Negative Temperature Coefficent or Positive Temperature Coefficient. Feed the output of the 2:1 Multiplexer into your BQ77915 thermistor input.