I have constructed one LM317T based Ni-Cd charger for 4 series cells. Charging voltage I applied is 6.30V. But in the battery pack, there is one 4007 diode is connected for safety. So there might be some voltage drop. The problem is as the charging is going on the output voltage also increased. I wondered y the current flow indicator doesn't stop. After some hours, I checked the output voltage it was 6.55 V! y this happens! Also what is the maximum charged voltage of a fully charged Ni-Cd AA cell.what is the voltage drop for 4007 I have to add for setting LM317?