The TP4056 is one of the most popular single-cell lithium battery charger ICs in the maker community — and for good reason. For under ₹50, this tiny module gives you a complete, USB-powered Li-ion charging circuit with LED status indicators, adjustable charge current, and optional protection against over-charge, over-discharge, and short circuits. Whether you are building a portable sensor, a DIY power bank, or a solar-charged device, understanding the TP4056 module is an essential skill for every electronics hobbyist in India.
Table of Contents
What is the TP4056?
The TP4056 is a complete constant-current/constant-voltage (CC/CV) linear charger IC designed specifically for single-cell 3.7V lithium-ion and lithium-polymer batteries. Manufactured by several Chinese IC houses (most commonly NanJing Top Power ASIC), it implements the standard Li-ion charge algorithm:
- Pre-charge (trickle): If the cell is deeply discharged (below ~3V), the IC applies a reduced current to safely recover it.
- Constant Current (CC): Charges at the programmed current (default 1A) until cell voltage approaches 4.2V.
- Constant Voltage (CV): Holds voltage at exactly 4.2V while current tapers down.
- Charge termination: When current drops below ~1/10 of the programmed rate, the IC declares the battery fully charged and turns off.
The IC itself measures just 2mm × 2mm in SOP-8 package, but the breakout modules available on Zbotic.in include all required passive components (resistors, capacitors, LED drivers) on a PCB roughly the size of a postage stamp.
Module Variants: With and Without Protection
When browsing TP4056 modules, you will find two main types. It is critical to know the difference:
| Feature | TP4056 Only | TP4056 + DW01A |
|---|---|---|
| Over-charge protection | Via TP4056 CV cutoff | ✓ Hardware cutoff |
| Over-discharge protection | ✗ None | ✓ Cuts off at ~2.5V |
| Short circuit protection | ✗ None | ✓ DW01A + FS8205A FETs |
| Safe for direct battery connection | With external BMS only | ✓ Yes |
| PCB size | Smaller | Slightly larger |
Always prefer the protected variant (TP4056 + DW01A) for any project where the battery will also power a load. The protection-only variant is fine if your load circuit has its own BMS, but for DIY power banks and standalone devices, the combined module is the safer and more practical choice.
Pinout and Connections
The typical TP4056 breakout module has the following pads:
- IN+ / IN− (or VIN/GND): Power input — connect to 5V USB or regulated 5V supply. Absolute maximum input is 8V, but always stay at 5V ±5% for reliable operation.
- BAT+ / BAT−: Battery terminals — connect directly to your 18650 or LiPo cell.
- OUT+ / OUT− (on protected modules): Load output — connect your circuit here instead of directly to the battery pads. This output is controlled by the DW01A protection IC.
5V USB ──────── IN+ BAT+ ──── Battery (+)
GND ──────── IN− BAT− ──── Battery (−)
OUT+ ──── Load (+)
OUT− ──── Load (−)Adjusting Charge Current
The TP4056 sets charge current via a single resistor (PROG pin to GND). The default module ships with a 1.2kΩ resistor for 1A charge current. You can desolder this resistor and replace it to change the current:
| PROG Resistor | Charge Current | Best For |
|---|---|---|
| 10kΩ | 130mA | Small LiPo cells (100–200mAh) |
| 4kΩ | 300mA | Thin LiPo cells |
| 2kΩ | 580mA | Smaller 18650 cells |
| 1.2kΩ (default) | 1000mA (1A) | Standard 18650 (≥2000mAh) |
A general safe rule: charge current in amps should not exceed the battery capacity in Ah (i.e., 1C max). For a 2000mAh cell, 1A (1C) is fine. For a small 500mAh LiPo pouch cell, reduce to 300–500mA by swapping the PROG resistor.
LED Indicators Explained
The TP4056 module has two onboard LEDs:
- Red LED on: Battery is charging (CC or CV phase active).
- Blue (or green) LED on: Charging complete. Battery is at 4.2V and current has tapered to near zero.
- Both LEDs off: No input power connected, or a battery fault (cell voltage too low for pre-charge to recover, or missing battery).
- Red LED blinking: On some modules, indicates the cell is in trickle pre-charge recovery mode (voltage below 3.0V).
Do not be alarmed if the blue LED turns on relatively quickly when topping up a partially charged cell — it simply means the CV phase terminated faster because the battery was already near full.
Building a USB Power Bank
A basic DIY USB power bank needs four components: an 18650 cell, a TP4056+protection module, a 5V boost converter (MT3608 or similar), and a USB-A output socket. Here is the assembly plan:
Micro USB Input
↓
[TP4056 + DW01A Module]
IN+ → 5V from USB
IN− → GND
BAT+ → 18650 (+)
BAT− → 18650 (−)
OUT+ → Boost Converter IN+
OUT− → Boost Converter IN−
↓
[MT3608 Boost Converter]
Output: 5V regulated
↓
USB-A Output SocketTotal BOM cost in India: TP4056 module (~₹45), 18650 cell (~₹200–400 for a genuine cell), MT3608 boost module (~₹30), USB-A socket (~₹10), 18650 holder (~₹20). Total: approximately ₹300–500 for a 3000mAh portable charger. The equivalent branded power bank costs ₹600–1200, but your DIY version uses quality cells you have personally verified.
Solar Charging Setup
The TP4056 can charge from a solar panel, but you need to manage one critical issue: solar panel voltage varies with sunlight and load. A 6V solar panel can output 7V+ in bright sun and drop below 4V in shade — both problematic for the TP4056.
The recommended approach is to add a buck converter between the solar panel and the TP4056 IN+ pin, set to output a stable 5V. This isolates the TP4056 from panel voltage swings. Alternatively, use a dedicated solar charge controller IC like the CN3791 which is designed specifically for MPPT-style solar-to-lithium charging. For small hobby setups (1W panel charging a single 18650 overnight), the TP4056 with a simple series diode and 5.1V zener clamp on the input works reasonably well.
Keep in mind: 1A charge current from a 1W panel is not feasible. A 1W panel at 5V delivers only 200mA. Either reduce the PROG resistor to 2kΩ (580mA) and use a 3W+ panel, or accept a slow charge rate from small panels.
Parallel Charging Multiple Cells
A single TP4056 module can only safely charge one cell at a time. To charge multiple cells, you need one module per cell. Do not connect multiple cells in parallel to a single TP4056 — the IC will see the combined capacity and may not terminate correctly, and if cells are at different states of charge, large equalisation currents can flow between them and damage cells or the module.
For multi-cell DIY battery packs, the correct approach is to build the full series pack and charge it through a BMS + appropriate balance charger, not with individual TP4056 modules per cell.
Load Sharing Circuit
A common problem in battery-powered designs is simultaneous charge and discharge (load sharing): you want the device to keep running while plugged in for charging. The TP4056 datasheet discourages connecting a load to OUT+ while charging, because the load current adds to the cell current and confuses the charge termination algorithm.
The proper solution is a load-sharing circuit using a P-channel MOSFET that automatically switches the load from the battery to the USB input when power is available. When USB is connected, the load draws from USB directly and the TP4056 charges the battery independently. Several reference designs for this circuit are available in the TP4056 datasheet and hobbyist forums. For simple projects, many makers simply accept the minor termination inaccuracy of direct load sharing — it rarely causes harm with decent cells.
Common Mistakes and Safety Tips
- Mistake #1 — Wrong polarity: Reversing BAT+ and BAT− will instantly destroy the module and potentially the cell. Always double-check polarity before first power-up.
- Mistake #2 — Input voltage too high: The TP4056 is rated for 8V maximum input. Using a 12V laptop charger directly will blow the IC. Use a 5V source only.
- Mistake #3 — Skipping protection on long-term installs: If your device will be left unattended (like a solar sensor in the field), always use the protected module variant. The over-discharge protection is critical when the device runs the battery flat.
- Mistake #4 — Using with LiFePO4 cells: The TP4056 charges to 4.2V, which is too high for LiFePO4 (max 3.65V). Using a TP4056 with LiFePO4 will over-charge and damage the cell. Use a TP4057 or other LiFePO4-specific charger IC instead.
- Mistake #5 — Charging a swollen cell: Inspect your cell before every charge cycle. A swollen (puffy) cell must never be charged — dispose of it safely immediately.
Frequently Asked Questions
Q: Can I use the TP4056 module to charge a 18650 directly?
Yes — connect the 18650 cell positive terminal to BAT+ and negative to BAT−. If using the protected variant, use OUT+/OUT− for any load. Provide 5V via Micro USB or directly to IN+ and IN−.
Q: Why does the blue LED light up immediately when I connect the battery?
The battery was likely already at or near full charge (4.1–4.2V). The TP4056 detects this and skips directly to the CV termination phase, which ends quickly. This is normal behaviour and not a fault.
Q: How long will it take to charge a 3000mAh 18650 with the TP4056 at 1A?
Approximately 3–3.5 hours from near-empty to full. Lithium charging is not perfectly linear — the CC phase takes roughly 70% of total time, and the CV taper phase takes the remaining 30%.
Q: Can the TP4056 charge LiPo (lithium polymer) cells?
Yes, as long as the LiPo cell is a standard 3.7V single-cell type. The charge algorithm and 4.2V termination voltage are the same for Li-ion and standard LiPo chemistries. Do not use with high-voltage LiHV cells (4.35V max), as the 4.2V termination will under-charge them.
Q: Is it safe to buy a TP4056 module from a local market for ₹10?
Exercise caution. Very cheap modules may use inferior ICs or have poor solder quality. For any project involving a battery you care about, spend slightly more to get a module from a reputable source. At ₹45–60, a quality module from Zbotic.in gives you reliable performance and consistent protection behaviour.
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