Morningstar, Remote Temperature Sensor, RTS
The Remote Temperature Sensor (RTS) from Morningstar increases battery charging in solar systems that undergo seasonal temperature changes. The RTS controls the temperature of the battery, and the controller uses this knowledge to make very precise temperature changes. If the temperature at the battery varies by more than 5°C (9°F) from the temperature at the controller, the RTS should be used.
Since the TriStar lacks on-board temperature compensation, temperature compensated charging requires the use of the RTS. If an RTS is not paired, other Morningstar controllers can use the on-board temperature sensor.