Input Voltage Range: 5V to 15V DC (Absolute maximum up to 18V). Output Voltage: 4.2V (1S mode) or 8.4V (2S series mode). Maximum Charging Current: 2A (Adjustable via on-board sampling resistors). Charging Stages: 3-phase system (Trickle pre-charge ,Constant Current,  Constant Voltage). Built-in Protections: Over-current, under-voltage, over-temperature, short-circuit, and battery reverse polarity protection. Configuration & How to Use   1. Switching Between 1S (4.2V) and 2S (8.4V) Modes  The module features an on-board solder jumper labeled ''SET''. 1S Mode (4.2V default): Leave the SET pads open (un-soldered). Input voltage can be as low as 5V (e.g., standard USB). 2S Mode (8.4V): Short/solder the ''SET'' pads together. You must increase your input voltage to a minimum of 10V–12V (a 12V DC power adapter works perfectly). 2. Adjusting the Charging Current Most standard modules come pre-configured for the maximum 2A output using two 0.1Ω resistors in parallel. If you are charging smaller batteries (like a standard 18650 cell that shouldn't exceed 1A), you can desolder or swap out the current-sensing resistors (Rs): 0.1Ω resistor: Sets current to 1A. Two 0.1Ω resistors in parallel (0.05Ω): Sets current to 2A. 3. Wiring Connections IN+ / IN-: Connect your input power source (5V for 1S, or 12V for 2S). BAT+ / BAT-: Connect directly to the positive and negative terminals of your battery pack. LED Header: Features three pads to solder an external, dual-color LED if you are mounting the board inside an enclosure. 4. LED Status Meanings Red LED On / Blue LED Off: Charging in progress. Blue (or Green) LED On / Red LED Off: Standby mode, fully charged, or no battery detected. 📌 Critical Working Notes No Internal Balancing: When using the TP5100 in 2S (8.4V) mode, it does not balance the two cells. It treats them as a single 8.4V block. If you are wiring two 18650 cells in series, you should ideally add a separate 2S BMS (Battery Management System) board between the charger and your batteries to ensure the cells stay balanced and safe. Heat Dissipation: While it runs cooler than linear modules, it can still get warm at a full 2A load. Ensure it has decent airflow if used continuously at maximum output. read more