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Bright LED panel on a 12 V LiFePO4 battery: low-voltage cut-off, CC/CV buck at 3 A, LED board

Bench build · Module builds · Intermediate · about 30 minutes

A steady, bright 10 W light from a 12 V battery that protects the battery by itself. LEDs want a set current, not a set voltage. A CC/CV buck module (XL4015) set to 4.2 V and 3 A drives a 24-LED board at about 125 mA per LED, whatever the battery is doing. A fuse and an on/off switch sit at the battery; after them a low-voltage disconnect module set to LiFePO4 switches the light off at 12.0 V so the battery is never run flat, and back on at 13.0 V. Turn the CV trimmer to 4.2 V first (just above what the board needs at 3 A, so the current limit is what sets the brightness), then short the output through a meter and set the CC trimmer to 3 A.

Bright LED panel on a 12 V LiFePO4 battery: low-voltage cut-off, CC/CV buck at 3 A, LED board: 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/bright-led-panel-12v

Parts list

Test procedure

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

  1. LED current (the CC setting)
  2. Battery current (less than the LED current)
  3. Battery almost empty: the light switches off

How it works

What it does: A steady, bright 10 W light from a 12 V battery that protects the battery by itself.

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

Constant-current drivers are why modern LED lights stay the same brightness until the battery is almost empty.

More builds: module builds