I do not know the reason why my mobile has come up with this problem. I have done nothing weird but still it gives me this problem. At night I left it for charging and in the morning when I switched on the mobile the battery was not fully charged. I tried again to charge the mobile phone, but as soon as I inserted the charger, it started to give me warning like: Unable to charge the battery. Please insert the Sony Ericsson Battery. I am sure that the battery is the original one. Any suggestions from your side.