Calculating CSTOR on BQ25504

I'm designing a solar chager to charge 3 Ni-MH AAA series batteries, using the BQ25504. Batteries I'm using has a equivalent capacitance of 3.6kF. So the 3 series batteries has 1.2kF of equivalent capacitance. It's series resistances is 30mohm, so the 3 series batteries has 90mohm of equivalent resistance. The time constant created by the storage element's series resistance (plus the resistance of the internal PFET switch) and the equivalent capacitance is T=(90 mohm + 2 ohm)*1.2 kF=2.5 ks. This parameter should be less than 45 ms, so I need to increase CSTOR or add an aditional capacitance to VBAT. How do I calculate the additional capacitance on VSTOR to satisfy the 45 ms max. window?