The notification will only happen when the Miles Tracker spots that the voltage on your car’s battery has dropped below 12 volts for a while. It doesn’t necessarily mean your battery’s health is poor, because even a healthy battery can sometimes drop below 12 volts (if, for example, the lights were left on).
If you aren’t aware of anything that might have caused this, there are a couple of reasons why the voltage may be low. If you have only driven short distances recently, it may be that the battery has not had time to be charged up fully by the car. Or, it may be the alternator (the charger) is worn out.
If you’re not sure, it may be worth getting your battery looked at or replaced if it’s older than three years.