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?
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.