# TP4056 charger module: LED meaning, wiring and what not to power from it

> Use a TP4056 lithium charging module: the red and blue or green LEDs, B+ and B- wiring, the protected version and loads on OUT.

Canonical: https://roboticsengineering.in/fix/tp4056-charger-module-led-meaning-and-wiring/ | Published: 2026-11-03 | Updated: 2026-11-04

**On most TP4056 modules a red LED means charging and a blue or green LED means finished.** Check your own board, since colours can differ.

## What the message means

The module charges a single lithium cell from 5 V. The basic version has no protection, while the version with extra chips adds protection for over-discharge and short circuit.

## Fix it in this order

1. Connect the cell to B+ and B-, and the 5 V input to IN+ and IN-. Check the polarity twice.
2. Charge only one cell at a time with this module.
3. Prefer the version with protection if the cell is not already protected.
4. Keep the load current within what the protection and the cell allow, and do not run a hungry motor from the OUT pins.
5. Do not charge an unattended cell on a flammable surface. Use a cell rated for the charge current.
6. Check the charge current setting resistor for your cell.

## Why it happens

The TP4056 is a linear charger for a single lithium cell. It takes a 5 V input, regulates a constant charge current into the cell, and stops when the cell reaches its full voltage. The indicator LEDs show the charging state, but LED colours vary between boards, so the markings and datasheet of your specific module are the reliable reference. The basic module has no protection circuit, so it cannot guard the cell against over-discharge or a short circuit.

Wiring mistakes cause most trouble. Reversed polarity on the cell or the input can damage the module, and connecting a load directly to the battery terminals bypasses any protection. Charging a cell that is not rated for the programmed current, or leaving one charging unattended, adds risk. Using a protected module or a protected cell, and keeping the load within its rating, removes most of these hazards.

## If you see this, do this

| You see | Do this |
| --- | --- |
| Both LEDs flicker | Poor cell connection or no cell. |
| Cell gets hot | Stop. Check polarity and charge current. |

## Confirm the fix

1. With the cell connected and the input off, measure B+ to B- with a multimeter and record the resting voltage.
2. Connect the 5 V supply and measure the cell again; the voltage should rise steadily during charging and never exceed the cell’s full-charge rating.
3. Once charging starts, check the cell by touch; if it grows noticeably warm, disconnect and re-check polarity and the charge current setting.

**Common mistake:** Readers assume the LED colour means the same state on every module, when colours differ between boards and checking the wiring is the real first step.

## Related

[lithium cell sag](https://roboticsengineering.in/fix/lithium-cell-voltage-sags-robot-resets/), [robot battery guide](https://roboticsengineering.in/robot-battery-guide/).

Last reviewed: November 2026. These are the usual causes and the order that finds them fastest. Test on your own board; clones and cables differ.