I would say that the odds of it fully charging the 5 cell pack are pretty low with any wall-wart charger for 4.8 volts. That's a nominal charge voltage. The typical fully charged 4 cell is over 5 volts and the normal fully charged voltage for a 6 volt pack is somewhere close to 7 volts.

You are better off using a proper charger for the 5 cell packs. There are many on the market for reasonable prices. I have three: An ICE, Triton, and the Hobbico Accucycle.

CGr.