The **RTS-5E-R** is an electronic thermal sensor, specifically a **Remote Temperature Sensor** commonly used in solar charge controllers (such as those from Renogy or EPEVER). Its primary function is to monitor the temperature of a battery bank to allow the controller to perform **temperature compensation**. --- ## 1. Technical Specifications The device is a passive sensor housed in a protective lug, connected to a long cable. | Feature | Description | | :--- | :--- | | **Sensor Type** | NTC Thermistor (Negative Temperature Coefficient) | | **Resistance** | Typically 10kΩ at 25°C | | **Connector** | 3.5mm Jack (TS or TRS) or RJ11 (depending on specific revision) | | **Cable Length** | 3 Meters (approx. 9.8 ft) | | **Accuracy** | ±1°C to ±2°C | | **Operating Range** | -55°C to +125°C | --- ## 2. Key Electronic Components ### A. The NTC Thermistor The core electronic part is the **NTC Thermistor**. - **Mechanism:** As the temperature of the battery rises, the electrical resistance of the thermistor decreases. - **Function:** The charge controller sends a small reference voltage through the sensor and measures the voltage drop to calculate the precise temperature. ### B. The Mounting Lug The sensor is encased in a **metallic ring terminal** (lug). This is not just for mounting; it acts as a thermal conductor, ensuring the heat from the battery terminal is efficiently transferred to the internal thermistor. ### C. The Transmission Line The cable uses shielded or twisted pair wiring to minimize **EMI (Electromagnetic Interference)**. Since the sensor operates on variable resistance, electrical noise from the solar panels or inverter could cause "ghost" temperature readings without proper insulation. --- ## 3. The Role in the Circuit When integrated into a power system, the RTS-5E-R performs the following electronic logic: 1. **Voltage Regulation:** Lead-acid batteries require higher charging voltages in cold weather and lower voltages in hot weather to prevent outgassing or "boiling." 2. **Safety Cut-off:** If the sensor detects a temperature above a specific threshold (e.g., 65°C), the controller's logic circuit will terminate the charging process to prevent thermal runaway. 3. **Efficiency:** By adjusting the charge profile based on real-time data, the electronic lifespan of the battery bank is significantly extended. --- ## 4. Connection Diagram (Simplified) ```text [ Battery Terminal ] <--- (Thermal Lug) --- [ NTC Thermistor ] | [ 2-Wire Cable ] | [ Charge Controller ] <--- (3.5mm Jack) ---------+ ```