The key purpose is that till your phone is obtaining around finishing charging, then the probabilities are that the power bank battery isn't charging much, if it all. depending on what proportion charging power your phone uses compared to the charging power of the power bank, you will even notice that the power bank battery is discharging a touch while the phone is charging, adding to the charging power going into the power bank to charge the phone additional quickly.
Though not all power banks support this feature, if yours does, you'll be able to assume its okay to make out. Some people could tell you that its not OK, because the power bank will age faster or die sooner. Though there's some truth behind, it will truly not make sense to something you have already paid for, unless you purchased it for collecting rather than using it.
Lithium-Ion batteries age with each cycle. This chemical action is process simply natural for lithium-ion accumulators. If you utilize it or not. it'll die anyway. It limits the period to 2 or 3 years once leaving the manufacturing plant. afterward the internal resistance can become soo high as only little of the positive plate is left, that the battery can simply not be able to deliver high currents without drop voltage any longer. thus knowing that your device is dying anyways, I counsel to use it as long and far as you'll be able to.
So the only concern is that you’re wasting power within the power bank electronics compared to charging your phone directly. this can be quite an bit of wasted electricity, however it'll cause some heating. the power bank electronics are designed to alter this, assumptive it’s an decent style, and as long because the room temperature isn't too high and you’re not concealing the power bank under something which will
keep the heat in.