As such the charger works very well. In terms of battery "naked" into the slot: a review involves the operation. This is REAL: we must "tweak" the battery in the location to a small red LED turns on and the battery charge properly. Furthermore: YES: it load slower when loading "phone + battery" simultaneously and YES it is normal. This product is not connecting directly to the mains BUT on a charger connected to a power outlet ==> this is the same amount of current available to the load of one phone or the battery alone or simultaneously 2: inevitably it lasts longer and even 2 times more if the two batteries have the same current capacity stored. Which brings me to the real plus of this device: it comes with 2 batteries of 4350 mili amp / hour. or a "capacity" of + 46% compared to original battery Samsung Galaxy Note 3. With 2 batteries ==> Over 3 days of autonomy (I am "zero" movie and video on my smartphone) . BRIEF: Go ahead without hesitation.