Battery is charging slowly..

[Starboy21]

My 540 on windows 10 build : 14393.1593 whenever connected to the charger shows that the device is charging slowly n it asked me to connect to the official charger n i hav connected it to the official charger still n today charging my phome frm 25 to 78 took 4 hrs so i removed the battery for some time n then put it back n then it showed as 98 i dnt think this is a battery issue as my phone still lasts a day which it normally did only the charging time has increased so plzz suggest me what shud i do now ???
Also when charging ur phone does the plug icon blink in every sec ??