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Solar floodlight, the module way: LiFePO4 charger board, BMS, LED board and a panel-sensed dusk switch

Bench build · Module builds · Beginner · about 40 minutes

Charges by day, lights by itself at night, and the BMS stops the cells being over-charged or run flat. A proper version of the cheap solar floodlight, from parts you can buy as boards. A 6 V 10 W panel feeds a TP5000 charger board set to LiFePO4 (3.6 V full), through a 1S LiFePO4 protection board, into two 32700 cells in parallel (12 Ah). The 24-LED board runs straight from the 3.2 V cells through its own small resistors: about 1.1 A (45 mA per LED, well under their 150 mA rating), so the cells last about 10 hours and the LEDs barely get warm. The dusk switch is one P-MOSFET and one resistor: by day the panel’s voltage holds the gate high and the light is off; at night the panel goes dark, R1 pulls the gate low and the light comes on. No light sensor needed: the panel is the sensor.

Solar floodlight, the module way: LiFePO4 charger board, BMS, LED board and a panel-sensed dusk switch: the finished build running on the simulator's bench

Build it in the labGuided build, test sheet and fault finding, free in your browser.

zencircuitlab.com/l/solar-floodlight-module-way

Parts list

Test procedure

Each test has an expected value and a pass range, like a factory test sheet:

  1. Full sun: the light stays off
  2. Full sun: charge current into the cells
  3. Night: the light comes on by itself
  4. Charged cells stop at LiFePO4 full

How it works

What it does: Charges by day, lights by itself at night, and the BMS stops the cells being over-charged or run flat.

Build it (guided or ready-made), then run its test procedure below. Every test has an expected value and a pass range, just like a factory test sheet.

Background

Most solar floodlights sold online skip the charger and the BMS and put the panel straight on the cells. Two small boards make the same light last for years.

More builds: module builds