I would do some basic research on chargers for Nimh cells and on your solar panels as well. At what latitude are you located? If your Winters are long there isn't really a lot of insolation available and I would make sure that you have about 150 to 200 % 'excess capacity available. A Nimh charger isn't really hard to make, Maxim makes some nice charge controllers as well as several others and you might find a charger on Ebay. Basic advice is to limit the charge to .1C(apacity) unless the data sheet for the batteries indicates otherwise. It's been my experience with Nicd as well as Nimh that you need to replace about 120% of what you've used for a full charge. If you look carefully at the data sheets for the chargers you can get a good insight for charging the batteries.
Bob