This Optional Battery Temperature Sensor (MC-TS-B) allows the Balmar Max Charge or ARS-5 voltage regulator to monitor and adjust charging voltages based on ambient battery temperature, ensuring accurate charging in warm or cold conditions. In addition, the sensor enables the regulator to discontinue charging and activate the regulator's Dash Lamp terminal if battery temperature exceeds safe limits. The MC-TS-B can also be used with Balmar's Digital Duo Charge to monitor for over-temperature conditions at the starting (secondary) battery bank while charging.