When I charge a 7.2 volt battery in either slot my “Fast battery charger” (the blue one) it buzzes. Sometimes it buzzes continuously and other times it is on and off. The battery seems to charge fine but it is sort of disconcerting, any ideas on what is happening?
Thanks 
How loud is the buzzing? Is it coming from the transformer or the charger itself? I don’t know for sure what it could be, but it can’t be good.
The buzzing is not very loud but is easily audible; it comes from the blue cradle and stops as soon as I unplug the battery.
I have a similar issue, but I just consider it to be the current running and no big deal. Not to mention it’s just one charger for me, so as long as I have other ones in case this one spazzes I’m fine with it.
Yep I have the same problem. I just unplug my charger when the batteries are done charging. I don’t think there’s anything wrong with your charger.
We’ve had this as well. There is a high-pitched buzzing that goes on/off with the red status LED.
Our batteries work fine, so not a problem.