Design challenge n.8: temperature sensors

A project log for Green BMS

Open source Bluetooth Smart Battery Management System

Sergio GhirardelliSergio Ghirardelli 10/18/2021 at 10:130 Comments

One of my goals in this project was to do a temperature control on each single cell module, in order to remove the enabling for charging and discharging in case of high temperature.

First I had to choose the type of sensor.

Due to the supply voltage ranges of the cell, I chose to use the TMP36 analog sensor that can be supplied between 2.7v and 5.5v.

TMP36 can detect temperatures from -40 °C to 125 °C.

While I was thinking about the most suitable point of the circuit where to install the sensor, I thought about one thing:

Why not include something more in my project than other BMS's? Why not also monitor the temperature of the balancing resistors, in order to interrupt the balancing in case of exceeding a threshold set by the user?

So I decided to add a second TMP36 for the resistors.

I placed the sensors like this:

To be more effective in the measurement, I fixed the sensor body with thermal glue to the point to be measured.

Thanks to this configuration, it is possible to monitor the temperature values of the pole (TP) and of the resistances (TB) in each cell at any time via the app.

Through the threshold parameters of high cell temperature and high balancing temperature, the user can decide above which pole temperature to remove the consent for battery charging and discharging and above which temperature of the resistors to stop balancing.

A possible improvement?

To add a Low temperature threshold parameter of the pole, below which to block the consent to charge the battery.

This thing will be done in the future evolution of the project ...