The level of battery with the simultaneous use and loading falls.

I welcome ! I have some problem with a battery. At the simultaneous use and loading the level of battery falls. I tested already two loaders from Sony Xperia Z3 and from Huawei. I thought, that then guilt of loader is thus I substituted her by new, but nothing acted then. A loader was purchased on an allegro and original. Today I noticed something strange, I connected a cable from Samsung Galaxy S2 to the loader and about a miracle loaded up during 4 hours, and always embarked 9 hours. I do not know in what is founded a problem. I apologize for my English.