Stefan Since I bought it I put it on charge when it gets around 20% and let it charge fully, to charge it I use either a power supply from Anker with the original cable, or a dock charge from Aukey. Charged like this for 2 years and until a few days ago no problem.
UPDATE: Tonight I tried charging the battery with the smartphone off and it recharged right away without any problem, so I think it is a software issue.