Rechargeable batteries are a great bargain when you compute their cost over their service life. Example:

24 eneloops are $33.00 (current price at Battery Junction) or $2.75 apiece. 2100 recharge cycles are claimed. Let's say that is exaggerated and you can only achieve 1000 cycles. That's less than 3 cents per cycle!

You can buy a charger made of solid gold with those savings, but my favorite is a Nitecore Intellicharger i4 - 4 independent channels, charges Nimh, NiCad, or lithium ion in a variety of sizes - C, AAA, AA, 18650, etc. It comes with cords for either 12V or 120 AC and is small enough to pack and carry on trips. Other comparable chargers are available.

These capabilities really came in handy for me last summer. Doing a paleontology dig, I began supplying about 4/5 lights for weird situations where shadows obscured visibility. At the end of each day, I would collect the lights, recharge the batts overnight, and repeat, for about three weeks - a lot less trouble, and cheaper, too.