You will want to get something with a voltage output as close to the battery that was hooked up to the board to start with. If you have one lying around I would try an early E-Spyder as I know they can take a variety of voltage inputs from a 7.2V NiMH to the 9.6 V java battery. I'm not certain of how a solar cell works but I believe their voltage output is related to the amount of light it is receiving.
As far as hairline cracks in the panels go,.. I don't think that effects them too much,... but I am not certain here. I know my calculators with hairline cracks in the panels still work fine, and as I said I haven't studied how a solar cell works internally so I'm not sure what effect this will have.
If you are going without a battery completely, once you get your solar bank built, all you will need to do is hook it up at the same place the battery was, making sure to hook up the positive and negative terminals right. If you are going to have a battery hooked up,... or even the option of one, please consider not charging it, but instead using a diode to keep it from being charge, and then hooking the battery up in parallel with the cells. This will prevent a potential fire hazard from over charging, unless you plan on building a battery charger that will prevent that.
