I have looked into NIiMh batterys and I would stick with Nicads. The NiMh have a faster self discharging rate and don't like to sit withour being used. They also take a few cycles to get back up to full rating after if they have been sitting for a week or so. If you only fly on weekends that means that the Nicads are far better suited to our hobby. If you fly every day then they would be ok. If you are getting into more battery packs of different sizes you may want to invest another 10 bucks over the charger as mentioned above and get a multi charger. It can charge 4 sets at once with different settings. Check the link below.
http://www2.towerhobbies.com/cgi-bin...&I=LXL331&P=ML [8D]