Below are some batteries that we recommend for your Nocturnal Lights.
Sanyo Eneloop Rechargeable Batteries

Nocturnal Lights encourages the use of rechargeable AA batteries to help preserve and protect the environment. After doing some testing with a variety of consumer chargers and batteries in the market, we found the Sanyo Eneloop batteries outperformed most of the batteries in the market. These batteries are great because they have an extremely long shelf life (1 year+) compared to traditional NiMH batteries, which will lose most of its charge in about 3 months. They usually come in multiples of twos and fours and the Eneloop chargers comes with a charger that can charge 4 batteries at once. The batteries works with any chargers in the market so if you choose to use any existing charger you will only need to buy the batteries. Depending on your dive pattern you may choose the combination of batteries and chargers that makes the most sense to your needs.
Here are some detailed information about the Eneloop Batteries:
http://www.eneloop.info/home/general-description.html
http://www.eneloop.info/home/why-eneloop.html
http://www.eneloop.info/home/performance-details.html
http://www.eneloop.info/home/technology.html
http://www.eneloop.info/home/faq.html
Additional Notes:
Most quick chargers for AA batteries, especially the 15 minute chargers, will not give the batteries a full charge and the voltage tends to drop very quickly. If you notice that your light does not perform up to specs please try a different battery, charger, or a combination of both. A lot of photographers have rechargeable AAs for their strobes and the drop in voltage from the quick charger may not be noticeable when using the strobe.