38899

The 38899, manufactured by Morningstar, provides improved battery charging in solar-panel systems that experience temperature variations during the year. This remote temperature sensor (RTS) measures temperature at the battery, and the controller uses this data for very accurate temperature compensation. Campbell Scientific recommends using the 38899 when the temperature at the battery will be more than 5°C (9°F) different from the temperature at the controller. For example, use the 38899 when the battery and charge controller are in different enclosures. 

For maximum protection from harsh environments, the sensor is encapsulated in epoxy inside a power lug housing. The 38899 is also protected from lightning surges and short circuits. Connect the RTS using its ring lug directly to either battery terminal.

Extending the Cable Length

The cable can be extended up to 30 m (100 ft). The original 10 m (33 ft) cable should be cut, and the new cable should be soldered into the middle. Solder the spliced wire connections, and tape or seal the bare wires. The new cable extension should be a shielded, twisted pair cable. At a minimum, the new wires should be at least 0.34 mm² (22 AWG); however, a larger size of 1.0 mm² (18 AWG) may provide better performance.