Every charger supply I've seen has the voltage printed on it, even if it's sometimes black embossed on black and therefore not obvious.

With a weird situation like this, it often helps (see my signature below) to tell us what equipment you have. For instance, back when the only consumer remote made by RTI was the Lexicon T500, that remote learned an IR code for a Somfy electric shade motor that sent out an IR signal so strong that it actually blew some LEDs working off of a Niles IR distribution system. Another time I had to back away a satellite remote about five feet from the Lexicon to keep it from sending out a signal that would overload the satellite's IR receiver and thus not work.

IR things are under much better control now (I ASSUME!), but revealing your exact product takes this problem out of the realm of the general and lets us use our experience with individual products.