The only thing which matter is the battery capacity and plug polarity, then you can charge over night at 1/10 capacity rate like any Nicad or Nimh. You might have to check the polarity at the charging socket,but if same as Airtronic the center pin is positive (Only JR/Spektrum is different). If you can't get any reading at the socket it mean there is a diode somewhere to protect against reverse polarity while charging. Since it is an off brand Tx maybe sold only locally its hard to know exactly, many of these are rebranded radios made for a specific retail outlet so you might have to do some PC board measuring to know what is what. The battery capacity and type should be somewhere on a label. Just did a search and found their site:
A German company, the radio indeed look sort like the old Airtronic 3 chanels for surface use. They have a pdf of the manual:
Instructions in English,German,French but not a word about the charger, this radio seems to be sold as dry cell .