No, there should not be any bad effects from leaving the battery plugged in.

Once the battery is at full charge, it will not allow any overcharging from the ac power. So there isn't any need to worry about it.

Im new here and need alittle info.I just bought a Inspiron 2500 used with no disk and my battery light just blinks about 2 hours then quits.but it isnt charged,it wont operate the computer.Do I need to replace it or is there something I need to do to charge it?Is the light suppose to flash or stay on green while charging?

                                           Thank you in advance Pawpawholdme