# TP4056 charging basics: what the chip does and what it doesn't > The TP4056 charges one Li-ion cell to 4.2 V at up to 1 A, set by one resistor. Input range, termination, protection and why you never charge unattended. [HTML version](https://soldr.ai/blog/tp4056-charging-basics) 8 November 2026 · Soldr **Short answer:** the TP4056 charges **one** lithium-ion cell to a fixed 4.2 V, at up to 1 A set by a single resistor, and stops when the current falls to a tenth of that. It takes 4.0 to 8.0 V in. It does not protect the cell from over-discharge or a short on its own; modules add a separate protection chip for that. Use cells rated for a 4.2 V charge, charge at or below the cell's rated current, and never leave a charging lithium cell unattended. The small blue TP4056 board with a USB socket is how many projects add a rechargeable battery. It's a good chip, used within its limits. Here's what its datasheet says, as cited on our [TP4056 reference page](https://soldr.ai/docs/components/tp4056-charger), and the board-level details the datasheet doesn't cover. ## What the datasheet says - **Input:** 4.0 to 8.0 V (5 V typical), absolute maximum 8 V. - **Float (full-charge) voltage:** 4.2 V, ±1.5 % (4.137 to 4.263 V). - **Charge current:** up to 1000 mA, set by one resistor on the PROG pin. The datasheet table runs from 10 kΩ = 130 mA to 1.2 kΩ = 1000 mA. - **Termination:** charging ends when the current drops to 1/10 of the programmed value. - **Temperature input:** the TEMP pin can watch a thermistor in the battery pack. Charging pauses if TEMP stays below 45 % or above 80 % of the input voltage for more than 0.15 s. Grounding the pin disables the check. ## Match the cell to the charger - **One cell only.** The TP4056 charges a single cell. Cells in series need a charger made for that. - **4.2 V chemistry only.** Use it with lithium-ion or lithium-polymer cells whose datasheet gives 4.2 V as the full-charge voltage. Cells with a different full-charge voltage need a different charger. - **Charge current at or below the cell's rating.** Small pouch cells often have a low maximum charge current. Check the resistor on your module's PROG pin against the table above, and change it if the module charges faster than your cell allows. ## Protection is a separate chip The TP4056 controls charging. It doesn't cut the battery off if your project drains it too far, or if the output is shorted. Many modules add a protection chip (often a DW01A with a pair of MOSFETs) and separate output pads for the load. That's a module feature, and no official document covers it, so look at your board: - **Battery pads** (often B+ and B−) go to the cell. - **Output pads** (often OUT+ and OUT−), on modules that have them, go to your project, so the load is behind the protection. - If your module has no protection chip, use a protected cell, or add protection. ## Safe charging habits Lithium cells store a lot of energy. A damaged, punctured or overcharged cell can swell, vent or catch fire. So: - **Never charge unattended**, and never overnight. Stay nearby, and unplug when you leave. - **Charge on a non-flammable surface**, away from paper, fabric and other things that can burn. - **Stop using any cell that's swollen, dented, punctured or hot**, and dispose of it properly. - **Respect the input range.** 8 V is the chip's absolute maximum; a 5 V USB supply is the intended input. - **Let it cool.** At high charge current the chip gets warm; give the module some air. ## Using it in a build A typical portable project is a cell, a TP4056 module with protection, and the board powered from the module's output. An ESP32 or NodeMCU board needs 3.3 V from its regulator, and a cell's voltage falls as it discharges, so check how your board's regulator behaves near the bottom of the cell's range. Our [power budget guide](https://soldr.ai/blog/esp32-arduino-power-budget-usb) covers adding up the current. Soldr's reference pages apply the same rule to project ideas on battery parts: none suggests leaving a battery charging unattended. When you describe a battery build, say what cell you have ("a single 3.7 V LiPo cell, 1000 mAh"), so the parts and power plan fit it. On Compoden: [TP4056 charger module with protection](https://compoden.com/products/tp4056-1a-li-ion-charger-module-with-protection-micro-usb). Describe your build on [app.soldr.ai](https://app.soldr.ai). Sign in and get 100 credits free.