LG G2 Mini battery (?) Problem

A

AC Question

Hi,
I bought a LG G2 Mini second hand that has been used for about 7 months...sometimes it takes 2-3 hours to get full charge and other times it takes 5-7 hours with the same charger and conection (the charger that came with the device and the wall conection), it doesnt even say that its on a slow charge

It happens sometimes also that the battery gets drained for no reason, leaving it iddle with only wifi and 2g it can las betwin 20 hours and 240 (the last one was only once, generaly what i feel happy to get is 120)

Thanks