Wednesday 29 January 2020

batteries - Is it OK to reduce the charging current for a Li-ion 18650 battery?


I am using NCR18650 batteries with the tp4056 charging module.


When I connect the charger at 2.8 V (fully discharged), the tp4056 IC is getting hot at a 1 A charge current. Is it OK to reduce this charge current by changing the charge current selecting resistor? So the tp4056 IC heat would be reduced, wouldn't it?


For my application I don't need a quick charge. With a low current, charging time will be increased, but it does not matter for my application.


Will reducing the charge current affect the battery's lifetime? Or will it damage the battery?


I am trying to reduce the heat of the tp4056 IC by reducing the charging current, maybe from 1 A to 500 mA or less. The 18650 battery never heats for a 1 A charge current.



Answer



I use TP4056 charger boards a lot, both on their own and embedded in some devices. In addition to existing answers, I'd like to mention this - it's OK for TP4056 to heat up, it's a linear charger and it heating up doesn't impact its performance/reliability all that much. As long as the board has proper heatsinking, you should be fine - i.e. the popular "blue PCB with USB port" chargers from China have good enough heatsinking, as they tend to connect the ground pad of the TP4056 to copper-filled areas on both layers (sometimes only one, bottom one, with vias).


If it's a custom board that you yourself designed and it doesn't connect the ground pad to anywhere useful, only then I'd be worried - in that case, swapping the current set resistor for ~2K (that's what you need for ~500mA IIRC) should do the job. Otherwise, you should be fine as you are now, with 1A charging.


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