I'm building a portable Bluetooth speaker that uses Arduino Pro Mini as switch controller, so the Arduino will always turned on, it consumes a little current, about 5 mA or even less.

I'm using TP4056 for the charging board.

I heard people say that charging battery while it taking load is bad, however, my load is so small, will it also be a problem?


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    \$\begingroup\$ Can you show us a schematic that you are using? \$\endgroup\$ Sep 3, 2021 at 10:43
  • \$\begingroup\$ It depends on the chemistry of the battery you're using, what type is it? The problem with lithium is the termination current sensing if the load current is not known. \$\endgroup\$
    – Neil_UK
    Sep 3, 2021 at 11:09
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    \$\begingroup\$ Please note that the sentence "charging battery while it is taking load" is fundamentally incorrect. The current is either flowing into the battery, so you are charging it, or it is flowing out of the battery, so you are discharging it. It is not possible for the current to be both positive and negative at the same time. \$\endgroup\$ Sep 3, 2021 at 11:41

1 Answer 1


The TP4056 cards are normally preset for 1A charge and 10% cutoff or 100 mA. The reason it is bad to charge while using, is the current is only sensed on the charger output not the battery alone.

If the load took most of the 100 mA cutoff, the charger would never cut off and the battery's cycle rate of 500 or less would be cut according the time spent with the charger on > 3.9V.

So adding 5 mA load means the cutoff is now 95 mA which is OK.

If the load were 50 mA, I would want the cutoff to be 4.1V but it's pre-fixed.

For the longest lifespan/ charge cycles, battery University reports using the capacity between 25% and 75% is best. But if you reduce the CV voltage from 4.2 towards 3.9V you will lose some mAh capacity this way, but can get 10 times total mAhr life usage out of it.


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