No, it won't work. Most wall wart chargers that come with your radio have an output voltage of 6 volts. This is what is needed to fully charge a 4-cell (4.8v) pack. These cells are fully charged when they are at 1.5v, so 4 cells times 1.5 volts/cell equals a total voltage of 6 volts. To fully charge a 5 cell (6 volt) batter you are going to need a charger that can put out 7.5 volts in order to fully charge that battery.

Ken