Battery recharging via solar panel
Vpanel >> Vbattery so panel acts as ~~ constant current source.

2 batteries in series or 4 batteries in series will still be &lt;&lt; 9V so charge in the same time.

Imp &lt; Icharge &lt; Isc  or
0.33A &lt; Icharge &lt; 0.43A

Say ~~= 350 mA.

T charge ~= Battery_mAh / Ichg  x 100 / Battery_efficiency  %
NimH CURRENT acceptance efficiency probably 80%-90%  

= 700 Mah / 350 mA x 100/80 ~~~= 2.5 hours

That's in full mid-day sun with panel square on to sun.
Charge for longer than this and you will quickly "cook" the batteries.
Vbattery_max at that charge rate should probably not be more than about 1.5V/cell when charging. 

Google:           your_city_name   gaisma
eg     Bangalore gaisma   gives  

    http://www.gaisma.com/en/location/bangalore.html


to get SSH = sunshine hours per day (= kWh/m^2/day)
Your panel will produce ABOUT  350 mA  x SSH  mAh per day

Bangalore example - 

Half a day on an average day will be more than enough in any month - see below.



Chart from Gaisma entry for Bangalore as above.