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Docs Power & Battery TP4056 Charging Current

TP4056 Charging Current

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How the TP4056 sets its charging current, the programming resistor values, and the trade-offs of fast versus slow charging.

TP4056 Charging Current

The TP4056 charges at a current set by one resistor. This page is the resistor math, the standard values, and the honest trade-offs.

The programming resistor

The charging current is set by Rprog between the PROG pin and ground:

CODE
I_charge (A) = 1200 / Rprog (ohms)
RprogCharging current
1.2 k1.0 A (the common default)
2.0 k0.6 A
3.0 k0.4 A
10 k0.12 A

The trade-offs

CurrentCharge time (2500 mAh)HeatCell stress
1.0 A~3 hNoticeableNormal
0.5 A~6 hLowGentler
0.2 A~15 hMinimalGentlest

The recommended value for the beacon: 0.5 - 1.0 A. Faster than 1 A exceeds the module’s spec and stresses the cell; slower than 0.3 A means overnight charging for a day trip.

The USB input limit

The TP4056 input current is limited by the source: a 500 mA USB port charges at 500 mA regardless of Rprog. The Charger Troubleshooting page covers the input side.

The thermal behavior

At 1 A the TP4056 and the cell both warm up. This is normal; a hot-to-the-touch board is not (see Charger Troubleshooting). In winter the warmth is even welcome (see Cold Weather Batteries).