It will have two wires. One is red or orange, the other is black or brown. The red is the + and the black is the -. Connect the colors to colors.. red to red, black to black. (or orange to red.. brown to black) and you will have good connection and it should charge. You can probably see the number of cells in the battery pack. If it has four cells, then it's 4.8 volts ( and most likely is what it is). If it has five cells, then it's a 6 volt pack and probably not good to charge on the wall wart charger.