yes you can use it but with a wall wart the voltage is inversly propotioanl to the current .. so the higher the voltage output the lower the current will be.. also its mA not mAh, mAh is a messure of capacity not charge current..
with a 4 cell pack you will get a 100mA charge current, with a 5 cell pack you will get less probably about 70-80mA.. so it will charge slightly faster than the 50mA 5cell charger you have.
check it out here
http://www.rcbatteryclinic.com/