TP4056 Charge Current Calculator – RPROG, Heat & Cutoff

Answer

I_BAT = 1200 V / R_PROG (V_PROG = 1 V in constant-current mode). For 1 A use 1.2 kΩ; for 500 mA use 2.4 kΩ. The chip dissipates (V_CC − V_BAT) × I_BAT and starts cutting the current when the die reaches about 145 °C. Source: NanJing Top Power TP4056 datasheet REV 2.0, Electrical Characteristics and Application Information.

Calculator

Target I_BAT (mA) Or RPROG (Ω) Cell capacity (mAh) VCC (V) V_BAT 1 (V) V_BAT 2 (V) V_BAT 3 (V) θJA (°C/W) Ta (°C) Resistor series

RPROG exact: 2 kΩ
RPROG nearest: 2 kΩ
I_BAT from exact R: 600 mA
I_BAT from nearest R: 600 mA
Application-table current: 580 mA
C-rate: 0.50 C
Trickle / termination: 60 mA / 60 mA
Recharge threshold: 4.05 V

V_BAT	Dissipation	Tj	I max without throttle	Throttles
3.0 V	1.2 W	175 °C	480 mA	Yes
3.6 V	840 mW	130 °C	685.71 mA	No
4.2 V	480 mW	85 °C	1.2 A	No

pass Supply voltage: VCC = 5 V. Operating / abs max is 4.0–8.0 V.
pass C-rate: Charge rate is 0.50 C. Warn above 1 C; check the cell datasheet.
fail Junction at V_BAT=3 V: Tj ≈ 175 °C. Thermal regulation will reduce current. I_max ≈ 0.48 A.
warn Junction at V_BAT=3.6 V: Tj ≈ 130 °C (P = 0.84 W).
pass Junction at V_BAT=4.2 V: Tj ≈ 85 °C (P = 0.48 W).

How it works

In constant-current mode the TP4056 holds PROG at 1 V. During pre-charge, PROG sits at 0.1 V. That is I_BAT = 1200 × V_PROG / R_PROG. Float voltage is 4.2 V ±1% (4.158–4.242 V). Charging stops once PROG has stayed below 100 mV for about 1.8 ms, which is C/10. Operating V_CC is 4.0–8.0 V, and 8 V is also the absolute maximum. Above a die temperature of about 145 °C, internal thermal regulation lowers the charge current. The datasheet also says about 140 °C on one page, with current reaching zero above 150 °C.

The calculator uses the formula as the reference and, when the nearest R_PROG is in the datasheet application table, shows that table current beside it. Trickle and termination are both I/10. Recharge is about 150 mV below 4.2 V (about 4.05 V). Junction temperature is Tj = Ta + (V_CC − V_BAT) × I × θJA, with θJA defaulting to 125 °C/W from the datasheet thermal example. The highest current that stays under 145 °C is I_max = (145 − Ta) / θJA / (V_CC − V_BAT).

Part numbers

Part	Package	Datasheet
TP4056 (NanJing Top Power)	SOP-8 with exposed pad	REV 2.0
R_PROG	0603 resistor, the value from the calculator	—

This card is for information only. Ordering suffixes are not listed because they have not been checked against the maker’s ordering table.

Disclaimer

Values come from the manufacturer datasheet listed above, as read on 26 Oct 2026. Calculations are estimates based on datasheet typical and maximum values plus the θJA you enter. Real temperatures depend on the PCB, airflow and enclosure. Before production, check the current datasheet for the exact part and lot, and verify on the bench. Lithium cells can be hazardous, so follow the cell maker’s charging limits.

Updated: 2026-10-26 · Jasper

Parameters used on this page

Parameter	Value	Source
Current-set formula	I_BAT = 1200 × V_PROG / R_PROG	TP4056 REV 2.0, Application Information
V_PROG (CC / pre-charge)	1 V / 0.1 V	Electrical Characteristics
I_BAT at R_PROG 1.2 kΩ	950 / 1000 / 1050 mA (min/typ/max)	Electrical Characteristics
Float voltage	4.2 V ±1%	Electrical Characteristics
Trickle threshold / current	2.9 V / I/10	Electrical Characteristics
Termination	PROG below 100 mV for about 1.8 ms (C/10)	Electrical Characteristics
Recharge threshold	100–200 mV below float, typ 150 mV	Electrical Characteristics
V_CC range / abs max	4.0–8.0 V / 8 V	Electrical Characteristics; Absolute Maximum Ratings
Thermal regulation	about 145 °C	Electrical Characteristics
TEMP pin	disabled by grounding the TEMP pin	Pin Function

Worked examples

A 1200 mAh cell at 0.5 C needs 600 mA, so R_PROG = 2.0 kΩ. The formula gives 600 mA; the datasheet application table lists 580 mA for 2 kΩ. At 5 V, θJA 125 °C/W and Ta 25 °C, V_BAT = 3.6 V dissipates 0.84 W (Tj about 130 °C) and V_BAT = 3.0 V dissipates 1.2 W (the chip throttles; I_max about 0.48 A). A 1.2 kΩ "1 A" module is 1000 mA by the formula and 900 mA in the application table, and at 3.6 V it will throttle (I_max about 0.69 A).

Pitfalls

Trusting a "1.2k = 1A" table. The datasheet application table and the formula disagree (900 mA vs 1000 mA at 1.2 kΩ).
Estimating heat at 4.2 V only. The hottest part of the cycle is constant-current charging at low cell voltage (about 3.0–3.6 V).
Leaving TEMP floating. Without an NTC, TEMP must be tied to GND.
Assuming the TP4056 protects the cell. The datasheet lists no cell over-discharge or over-current protection, so add a battery protection IC.
Reading a blinking CHRG LED as a fault. With no battery and 10 µF on BAT, a CHRG blink period of about 1–4 s is the datasheet no-battery indication.
Plugging in a 9 V adapter. That exceeds the 8 V absolute maximum.

FAQ

What resistor gives 1 A on a TP4056?

1.2 kΩ by the formula (1200 / 1.2 k). The datasheet application table lists 900 mA for 1.2 kΩ, and the charger may throttle from heat, so run the thermal check.

Why does my TP4056 get hot or charge slower than I set?

Thermal regulation near 145 °C. At 5 V in, a 3.6 V cell and 1 A, the chip dissipates 1.4 W.

Can a TP4056 charge from 9 V?

No. The absolute maximum is 8 V.

What is the TP4056 trickle current?

One tenth of the set current while the cell is below 2.9 V.

Does the TP4056 protect the battery?

No. The datasheet lists no cell over-discharge or over-current protection, so add a battery protection IC.

When does the TP4056 stop charging?

When the current falls to C/10 (PROG below 100 mV) once the cell is at 4.2 V.

Sources

NanJing Top Power, TP4056 datasheet REV 2.0: https://www.toppwr.com/uploadfile/file/20230304/640301eae1260.pdf (checked 2026-10-26).
Updated: 2026-10-26. Jasper.