You cannot use NIMH batteries in a fixture meant for NI-CD. The way that the batteries work is completely different in terms of how the solar panel works.
You need to take these out and get the correct kind, or the fixtures will work for a little while, but will be destroyed. This is true for all electronic devices, not just solar lights. you can fry a laptop or cell phone doing this.
Once you get the correct lights, the "Recharge" period means that you put the correct new batteries in and then leave them in the sun for two full days (shutting them off) or taking them in at night for 2 days.
By the way, it is VERY unusual to have any solar light that has a battery in one area and solar panel in another. They only ones of these that are common are those that are used for flood or spot lights which have 10-15 foot cords so you can place non-halogen fixtures inside. Very few lamps or accent lights have this fixture and futhermore, a well-built solar light and battery is meant to withstand the sun's heat.
So, Monday leave them in the sun, take them in Monday night or shut them off. Put them out Tuesday, then you can leave them to automatically turn on. You need to do this again to prevent damage to the various components. By letting the batteries charge fully with the sun, they work better. Trying to run something on a drained battery runs the battery down, lowers it's life cycle.