Does a dead 1.2V rechargeable AA NiCad battery act as an open or closed circuit? My electric toothbrush's rechargeable battery recently died and the manufacturer expects me to replace the entire unit. Personally, I think that's a waste of money so I've already opened it up and I can see the battery. However, instead of simply replacing the battery, I'd rather hook it up to an external power supply so that I will never have to worry about the battery again. It is easy for me to hook it up in an external power supply but the problem is that the battery is housed pretty tightly inside the unit and therefore, I am trying to avoid removing the battery because I might break the housing. Once again, I am planning to leave the battery where it is, drain the battery so that it is completely dead, and hooking up the external power supply. This will only work if the battery acts as an open circuit when it is dead. Does a dead 1.2V rechargeable AA NiCad battery act as an open or closed circuit?