I am using a TP4056 to charge a 18650 LiIon cell as shown in the circuit below. The BAT output is connected to the 18650 cell through a BQ29700 protection IC. According to the datasheet of the TP4056, the green LED should light up when the cell is fully charged. However, what happens is that when the green LED is on, the red LED also comes on. Why could this be the case? Theoretically, there shouldn't be any interaction between the TP4056 and BQ29700 since the float voltage output of the TP4056 is 4.26V max and the overvoltage threshold of the BQ29700 is 4.275V. enter image description here enter image description here

  • \$\begingroup\$ This would be a better question if the schematic showed your actual circuit, instead of just half of it, and you linked to both IC's datasheets. \$\endgroup\$ – Brian Drummond Jul 16 at 11:25

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