battery problems

hey guys new here and having some problems here just bought a 07 700 FI EPS and the battery doesnt seem to hold a charge and once it stalls an err_1 shows up and i think the number 46 i just recharged the battery on friday overnight and put it back in saturday morning it ran and started good all day then on sunday we were driving it around and the engine light came on so i turned it off thinking there was a problem and tried to restart it and the battery was dead again and suggestions please i am not very good with mechanics thank you