If your using a proper lipo charger then it will charge in 2 stages, CC (constant Current) and CV (constant voltage). It first charges in CC at a set rate of charge untill the voltage starts to get close to the 4.2v per cell level. It then switched to CV at 4.2v untill the battery is charged. As it's getting nearer the end of it's charge the current from the charger should decrease and the voltage stay the same. If your charger is going over 4.2v then I would stop using it ASAP.